gpencil_paint.c

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2008, Blender Foundation, Joshua Leung
 * This is a new part of Blender
 *
 * Contributor(s): Joshua Leung
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include "MEM_guardedalloc.h"

#include "BLI_blenlib.h"
#include "BLI_math.h"
#include "BLI_utildefines.h"

#include "BKE_gpencil.h"
#include "BKE_context.h"
#include "BKE_global.h"
#include "BKE_report.h"

#include "DNA_object_types.h"
#include "DNA_scene_types.h"
#include "DNA_gpencil_types.h"
#include "DNA_windowmanager_types.h"

#include "UI_view2d.h"

#include "ED_gpencil.h"
#include "ED_screen.h"
#include "ED_view3d.h"

#include "RNA_access.h"

#include "RNA_define.h"
#include "WM_api.h"
#include "WM_types.h"

#include "gpencil_intern.h"

/* ******************************************* */
/* 'Globals' and Defines */

/* Temporary 'Stroke' Operation data */
typedef struct tGPsdata {
    Scene *scene;       /* current scene from context */
    
    wmWindow *win;      /* window where painting originated */
    ScrArea *sa;        /* area where painting originated */
    ARegion *ar;        /* region where painting originated */
    View2D *v2d;        /* needed for GP_STROKE_2DSPACE */
    rctf *subrect;      /* for using the camera rect within the 3d view */
    rctf subrect_data;
    
    
#if 0 // XXX review this 2d image stuff...
    ImBuf *ibuf;        /* needed for GP_STROKE_2DIMAGE */
    struct IBufViewSettings {
        int offsx, offsy;           /* offsets */
        int sizex, sizey;           /* dimensions to use as scale-factor */
    } im2d_settings;    /* needed for GP_STROKE_2DIMAGE */
#endif
    
    PointerRNA ownerPtr;/* pointer to owner of gp-datablock */
    bGPdata *gpd;       /* gp-datablock layer comes from */
    bGPDlayer *gpl;     /* layer we're working on */
    bGPDframe *gpf;     /* frame we're working on */
    
    short status;       /* current status of painting */
    short paintmode;    /* mode for painting */
    
    int mval[2];        /* current mouse-position */
    int mvalo[2];       /* previous recorded mouse-position */
    
    float pressure;     /* current stylus pressure */
    float opressure;    /* previous stylus pressure */
    
    short radius;       /* radius of influence for eraser */
    short flags;        /* flags that can get set during runtime */

    float imat[4][4];   /* inverted transformation matrix applying when converting coords from screen-space
                         * to region space */

    float custom_color[4]; /* custom color for (?) */
} tGPsdata;

/* values for tGPsdata->status */
enum {
    GP_STATUS_IDLING = 0,   /* stroke isn't in progress yet */
    GP_STATUS_PAINTING,     /* a stroke is in progress */
    GP_STATUS_ERROR,        /* something wasn't correctly set up */
    GP_STATUS_DONE          /* painting done */
};

/* Return flags for adding points to stroke buffer */
enum {
    GP_STROKEADD_INVALID    = -2,       /* error occurred - insufficient info to do so */
    GP_STROKEADD_OVERFLOW   = -1,       /* error occurred - cannot fit any more points */
    GP_STROKEADD_NORMAL,                /* point was successfully added */
    GP_STROKEADD_FULL                   /* cannot add any more points to buffer */
};

/* Runtime flags */
enum {
    GP_PAINTFLAG_FIRSTRUN       = (1<<0),   /* operator just started */
    GP_PAINTFLAG_STROKEADDED    = (1<<1)    /* stroke was already added during draw session */
};

/* ------ */

/* maximum sizes of gp-session buffer */
#define GP_STROKE_BUFFER_MAX    5000

/* Macros for accessing sensitivity thresholds... */
    /* minimum number of pixels mouse should move before new point created */
#define MIN_MANHATTEN_PX    (U.gp_manhattendist)
    /* minimum length of new segment before new point can be added */
#define MIN_EUCLIDEAN_PX    (U.gp_euclideandist)

/* ------ */
/* Forward defines for some functions... */

static void gp_session_validatebuffer(tGPsdata *p);

/* ******************************************* */
/* Context Wrangling... */

/* check if context is suitable for drawing */
static int gpencil_draw_poll (bContext *C)
{
    if (ED_operator_regionactive(C)) {
        /* check if current context can support GPencil data */
        if (gpencil_data_get_pointers(C, NULL) != NULL) {
            /* check if Grease Pencil isn't already running */
            if (ED_gpencil_session_active() == 0)
                return 1;
            else
                CTX_wm_operator_poll_msg_set(C, "Grease Pencil operator is already active");
        }
        else {
            CTX_wm_operator_poll_msg_set(C, "Failed to find Grease Pencil data to draw into");
        }
    }
    else {
        CTX_wm_operator_poll_msg_set(C, "Active region not set");
    }
    
    return 0;
}

/* check if projecting strokes into 3d-geometry in the 3D-View */
static int gpencil_project_check (tGPsdata *p)
{
    bGPdata *gpd= p->gpd;
    return ((gpd->sbuffer_sflag & GP_STROKE_3DSPACE) && (p->gpd->flag & (GP_DATA_DEPTH_VIEW | GP_DATA_DEPTH_STROKE)));
}

/* ******************************************* */
/* Calculations/Conversions */

/* Utilities --------------------------------- */

/* get the reference point for stroke-point conversions */
static void gp_get_3d_reference (tGPsdata *p, float *vec)
{
    View3D *v3d= p->sa->spacedata.first;
    float *fp= give_cursor(p->scene, v3d);
    
    /* the reference point used depends on the owner... */
#if 0 // XXX: disabled for now, since we can't draw relative to the owner yet
    if (p->ownerPtr.type == &RNA_Object) 
    {
        Object *ob= (Object *)p->ownerPtr.data;
        
        /* active Object 
         *  - use relative distance of 3D-cursor from object center 
         */
        sub_v3_v3v3(vec, fp, ob->loc);
    }
    else
#endif  
    {
        /* use 3D-cursor */
        copy_v3_v3(vec, fp);
    }
}

/* Stroke Editing ---------------------------- */

/* check if the current mouse position is suitable for adding a new point */
static short gp_stroke_filtermval (tGPsdata *p, const int mval[2], int pmval[2])
{
    int dx= abs(mval[0] - pmval[0]);
    int dy= abs(mval[1] - pmval[1]);
    
    /* if buffer is empty, just let this go through (i.e. so that dots will work) */
    if (p->gpd->sbuffer_size == 0)
        return 1;
    
    /* check if mouse moved at least certain distance on both axes (best case) 
     *  - aims to eliminate some jitter-noise from input when trying to draw straight lines freehand
     */
    else if ((dx > MIN_MANHATTEN_PX) && (dy > MIN_MANHATTEN_PX))
        return 1;
    
    /* check if the distance since the last point is significant enough 
     *  - prevents points being added too densely
     *  - distance here doesn't use sqrt to prevent slowness... we should still be safe from overflows though
     */
    else if ((dx*dx + dy*dy) > MIN_EUCLIDEAN_PX*MIN_EUCLIDEAN_PX)
        return 1;
    
    /* mouse 'didn't move' */
    else
        return 0;
}

/* convert screen-coordinates to buffer-coordinates */
// XXX this method needs a total overhaul!
static void gp_stroke_convertcoords (tGPsdata *p, const int mval[2], float out[3], float *depth)
{
    bGPdata *gpd= p->gpd;
    
    /* in 3d-space - pt->x/y/z are 3 side-by-side floats */
    if (gpd->sbuffer_sflag & GP_STROKE_3DSPACE) {
        if (gpencil_project_check(p) && (ED_view3d_autodist_simple(p->ar, mval, out, 0, depth))) {
            /* projecting onto 3D-Geometry
             *  - nothing more needs to be done here, since view_autodist_simple() has already done it
             */
        }
        else {
            int mval_prj[2];
            float rvec[3], dvec[3];
            float mval_f[2];

            /* Current method just converts each point in screen-coordinates to
             * 3D-coordinates using the 3D-cursor as reference. In general, this
             * works OK, but it could of course be improved.
             *
             * TODO:
             *  - investigate using nearest point(s) on a previous stroke as
             *    reference point instead or as offset, for easier stroke matching
             */
            
            gp_get_3d_reference(p, rvec);
            
            /* method taken from editview.c - mouse_cursor() */
            project_int_noclip(p->ar, rvec, mval_prj);

            VECSUB2D(mval_f, mval_prj, mval);
            ED_view3d_win_to_delta(p->ar, mval_f, dvec);
            sub_v3_v3v3(out, rvec, dvec);
        }
    }
    
    /* 2d - on 'canvas' (assume that p->v2d is set) */
    else if ((gpd->sbuffer_sflag & GP_STROKE_2DSPACE) && (p->v2d)) {
        UI_view2d_region_to_view(p->v2d, mval[0], mval[1], &out[0], &out[1]);
        mul_v3_m4v3(out, p->imat, out);
    }
    
#if 0
    /* 2d - on image 'canvas' (assume that p->v2d is set) */
    else if (gpd->sbuffer_sflag & GP_STROKE_2DIMAGE) {
        int sizex, sizey, offsx, offsy;
        
        /* get stored settings 
         *  - assume that these have been set already (there are checks that set sane 'defaults' just in case)
         */
        sizex= p->im2d_settings.sizex;
        sizey= p->im2d_settings.sizey;
        offsx= p->im2d_settings.offsx;
        offsy= p->im2d_settings.offsy;
        
        /* calculate new points */
        out[0]= (float)(mval[0] - offsx) / (float)sizex;
        out[1]= (float)(mval[1] - offsy) / (float)sizey;
    }
#endif
    
    /* 2d - relative to screen (viewport area) */
    else {
        if (p->subrect == NULL) { /* normal 3D view */
            out[0] = (float)(mval[0]) / (float)(p->ar->winx) * 100;
            out[1] = (float)(mval[1]) / (float)(p->ar->winy) * 100;
        }
        else { /* camera view, use subrect */
            out[0]= ((mval[0] - p->subrect->xmin) / ((p->subrect->xmax - p->subrect->xmin))) * 100;
            out[1]= ((mval[1] - p->subrect->ymin) / ((p->subrect->ymax - p->subrect->ymin))) * 100;
        }
    }
}

/* add current stroke-point to buffer (returns whether point was successfully added) */
static short gp_stroke_addpoint (tGPsdata *p, const int mval[2], float pressure)
{
    bGPdata *gpd= p->gpd;
    tGPspoint *pt;
    
    /* check painting mode */
    if (p->paintmode == GP_PAINTMODE_DRAW_STRAIGHT) {
        /* straight lines only - i.e. only store start and end point in buffer */
        if (gpd->sbuffer_size == 0) {
            /* first point in buffer (start point) */
            pt= (tGPspoint *)(gpd->sbuffer);
            
            /* store settings */
            copy_v2_v2_int(&pt->x, mval);
            pt->pressure= pressure;
            
            /* increment buffer size */
            gpd->sbuffer_size++;
        }
        else {
            /* normally, we just reset the endpoint to the latest value 
             *  - assume that pointers for this are always valid...
             */
            pt= ((tGPspoint *)(gpd->sbuffer) + 1);
            
            /* store settings */
            copy_v2_v2_int(&pt->x, mval);
            pt->pressure= pressure;
            
            /* if this is just the second point we've added, increment the buffer size
             * so that it will be drawn properly...
             * otherwise, just leave it alone, otherwise we get problems
             */
            if (gpd->sbuffer_size != 2)
                gpd->sbuffer_size= 2;
        }
        
        /* can keep carrying on this way :) */
        return GP_STROKEADD_NORMAL;
    }
    else if (p->paintmode == GP_PAINTMODE_DRAW) { /* normal drawing */
        /* check if still room in buffer */
        if (gpd->sbuffer_size >= GP_STROKE_BUFFER_MAX)
            return GP_STROKEADD_OVERFLOW;
        
        /* get pointer to destination point */
        pt= ((tGPspoint *)(gpd->sbuffer) + gpd->sbuffer_size);
        
        /* store settings */
        copy_v2_v2_int(&pt->x, mval);
        pt->pressure= pressure;
        
        /* increment counters */
        gpd->sbuffer_size++;
        
        /* check if another operation can still occur */
        if (gpd->sbuffer_size == GP_STROKE_BUFFER_MAX)
            return GP_STROKEADD_FULL;
        else
            return GP_STROKEADD_NORMAL;
    }
    else if (p->paintmode == GP_PAINTMODE_DRAW_POLY) {
        /* get pointer to destination point */
        pt= (tGPspoint *)(gpd->sbuffer);

        /* store settings */
        copy_v2_v2_int(&pt->x, mval);
        pt->pressure= pressure;

        /* if there's stroke for this poly line session add (or replace last) point
         * to stroke. This allows to draw lines more interactively (see new segment
         * during mouse slide, i.e.) 
         */
        if (p->flags & GP_PAINTFLAG_STROKEADDED) {
            bGPDstroke *gps= p->gpf->strokes.last;
            bGPDspoint *pts;

            /* first time point is adding to temporary buffer -- need to allocate new point in stroke */
            if (gpd->sbuffer_size == 0) {
                gps->points = MEM_reallocN(gps->points, sizeof(bGPDspoint)*(gps->totpoints+1));
                gps->totpoints++;
            }

            pts = &gps->points[gps->totpoints-1];

            /* special case for poly lines: normally, depth is needed only when creating new stroke from buffer,
             * but poly lines are converting to stroke instantly, so initialize depth buffer before converting coordinates 
             */
            if (gpencil_project_check(p)) {
                View3D *v3d= p->sa->spacedata.first;

                view3d_region_operator_needs_opengl(p->win, p->ar);
                ED_view3d_autodist_init(p->scene, p->ar, v3d, (p->gpd->flag & GP_DATA_DEPTH_STROKE) ? 1:0);
            }

            /* convert screen-coordinates to appropriate coordinates (and store them) */
            gp_stroke_convertcoords(p, &pt->x, &pts->x, NULL);

            /* copy pressure */
            pts->pressure= pt->pressure;
        }

        /* increment counters */
        if (gpd->sbuffer_size == 0)
            gpd->sbuffer_size++;

        return GP_STROKEADD_NORMAL;
    }
    
    /* return invalid state for now... */
    return GP_STROKEADD_INVALID;
}


/* temp struct for gp_stroke_smooth() */
typedef struct tGpSmoothCo {
    int x;
    int y;
} tGpSmoothCo;

/* smooth a stroke (in buffer) before storing it */
static void gp_stroke_smooth (tGPsdata *p)
{
    bGPdata *gpd= p->gpd;
    tGpSmoothCo *smoothArray, *spc;
    int i=0, cmx=gpd->sbuffer_size;
    
    /* only smooth if smoothing is enabled, and we're not doing a straight line */
    if (!(U.gp_settings & GP_PAINT_DOSMOOTH) || ELEM(p->paintmode, GP_PAINTMODE_DRAW_STRAIGHT, GP_PAINTMODE_DRAW_POLY))
        return;
    
    /* don't try if less than 2 points in buffer */
    if ((cmx <= 2) || (gpd->sbuffer == NULL))
        return;
    
    /* create a temporary smoothing coordinates buffer, use to store calculated values to prevent sequential error */
    smoothArray = MEM_callocN(sizeof(tGpSmoothCo)*cmx, "gp_stroke_smooth smoothArray");
    
    /* first pass: calculate smoothing coordinates using weighted-averages */
    for (i=0, spc=smoothArray; i < gpd->sbuffer_size; i++, spc++) {
        const tGPspoint *pc= (((tGPspoint *)gpd->sbuffer) + i);
        const tGPspoint *pb= (i-1 > 0)?(pc-1):(pc);
        const tGPspoint *pa= (i-2 > 0)?(pc-2):(pb);
        const tGPspoint *pd= (i+1 < cmx)?(pc+1):(pc);
        const tGPspoint *pe= (i+2 < cmx)?(pc+2):(pd);
        
        spc->x= (int)(0.1*pa->x + 0.2*pb->x + 0.4*pc->x + 0.2*pd->x + 0.1*pe->x);
        spc->y= (int)(0.1*pa->y + 0.2*pb->y + 0.4*pc->y + 0.2*pd->y + 0.1*pe->y);
    }
    
    /* second pass: apply smoothed coordinates */
    for (i=0, spc=smoothArray; i < gpd->sbuffer_size; i++, spc++) {
        tGPspoint *pc= (((tGPspoint *)gpd->sbuffer) + i);

        copy_v2_v2_int(&pc->x, &spc->x);
    }
    
    /* free temp array */
    MEM_freeN(smoothArray);
}

/* simplify a stroke (in buffer) before storing it 
 *  - applies a reverse Chaikin filter
 *  - code adapted from etch-a-ton branch (editarmature_sketch.c)
 */
static void gp_stroke_simplify (tGPsdata *p)
{
    bGPdata *gpd= p->gpd;
    tGPspoint *old_points= (tGPspoint *)gpd->sbuffer;
    short num_points= gpd->sbuffer_size;
    short flag= gpd->sbuffer_sflag;
    short i, j;
    
    /* only simplify if simplification is enabled, and we're not doing a straight line */
    if (!(U.gp_settings & GP_PAINT_DOSIMPLIFY) || (p->paintmode == GP_PAINTMODE_DRAW_STRAIGHT))
        return;
    
    /* don't simplify if less than 4 points in buffer */
    if ((num_points <= 4) || (old_points == NULL))
        return;
        
    /* clear buffer (but don't free mem yet) so that we can write to it 
     *  - firstly set sbuffer to NULL, so a new one is allocated
     *  - secondly, reset flag after, as it gets cleared auto
     */
    gpd->sbuffer= NULL;
    gp_session_validatebuffer(p);
    gpd->sbuffer_sflag = flag;
    
/* macro used in loop to get position of new point
 *  - used due to the mixture of datatypes in use here
 */
#define GP_SIMPLIFY_AVPOINT(offs, sfac) \
    { \
        co[0] += (float)(old_points[offs].x * sfac); \
        co[1] += (float)(old_points[offs].y * sfac); \
        pressure += old_points[offs].pressure * sfac; \
    }
    
    for (i = 0, j = 0; i < num_points; i++)
    {
        if (i - j == 3)
        {
            float co[2], pressure;
            int mco[2];
            
            /* initialise values */
            co[0]= 0;
            co[1]= 0;
            pressure = 0;
            
            /* using macro, calculate new point */
            GP_SIMPLIFY_AVPOINT(j, -0.25f);
            GP_SIMPLIFY_AVPOINT(j+1, 0.75f);
            GP_SIMPLIFY_AVPOINT(j+2, 0.75f);
            GP_SIMPLIFY_AVPOINT(j+3, -0.25f);
            
            /* set values for adding */
            mco[0]= (int)co[0];
            mco[1]= (int)co[1];
            
            /* ignore return values on this... assume to be ok for now */
            gp_stroke_addpoint(p, mco, pressure);
            
            j += 2;
        }
    } 
    
    /* free old buffer */
    MEM_freeN(old_points);
}


/* make a new stroke from the buffer data */
static void gp_stroke_newfrombuffer (tGPsdata *p)
{
    bGPdata *gpd= p->gpd;
    bGPDstroke *gps;
    bGPDspoint *pt;
    tGPspoint *ptc;
    int i, totelem;
    /* since strokes are so fine, when using their depth we need a margin otherwise they might get missed */
    int depth_margin = (p->gpd->flag & GP_DATA_DEPTH_STROKE) ? 4 : 0;
    
    /* get total number of points to allocate space for 
     *  - drawing straight-lines only requires the endpoints
     */
    if (p->paintmode == GP_PAINTMODE_DRAW_STRAIGHT)
        totelem = (gpd->sbuffer_size >= 2) ? 2: gpd->sbuffer_size;
    else
        totelem = gpd->sbuffer_size;
    
    /* exit with error if no valid points from this stroke */
    if (totelem == 0) {
        if (G.f & G_DEBUG) 
            printf("Error: No valid points in stroke buffer to convert (tot=%d) \n", gpd->sbuffer_size);
        return;
    }
    
    /* special case for poly line -- for already added stroke during session
       coordinates are getting added to stroke immediatelly to allow more
       interactive behavior */
    if (p->paintmode == GP_PAINTMODE_DRAW_POLY) {
        if (p->flags & GP_PAINTFLAG_STROKEADDED)
            return;
    }

    /* allocate memory for a new stroke */
    gps= MEM_callocN(sizeof(bGPDstroke), "gp_stroke");
    
    /* copy appropriate settings for stroke */
    gps->totpoints= totelem;
    gps->thickness= p->gpl->thickness;
    gps->flag= gpd->sbuffer_sflag;
    
    /* allocate enough memory for a continuous array for storage points */
    gps->points= MEM_callocN(sizeof(bGPDspoint)*gps->totpoints, "gp_stroke_points");

    /* set pointer to first non-initialized point */
    pt= gps->points + (gps->totpoints - totelem);

    /* copy points from the buffer to the stroke */
    if (p->paintmode == GP_PAINTMODE_DRAW_STRAIGHT) {
        /* straight lines only -> only endpoints */
        {
            /* first point */
            ptc= gpd->sbuffer;
            
            /* convert screen-coordinates to appropriate coordinates (and store them) */
            gp_stroke_convertcoords(p, &ptc->x, &pt->x, NULL);
            
            /* copy pressure */
            pt->pressure= ptc->pressure;
            
            pt++;
        }
            
        if (totelem == 2) {
            /* last point if applicable */
            ptc= ((tGPspoint *)gpd->sbuffer) + (gpd->sbuffer_size - 1);
            
            /* convert screen-coordinates to appropriate coordinates (and store them) */
            gp_stroke_convertcoords(p, &ptc->x, &pt->x, NULL);
            
            /* copy pressure */
            pt->pressure= ptc->pressure;
        }
    }
    else if (p->paintmode == GP_PAINTMODE_DRAW_POLY) {
        /* first point */
        ptc= gpd->sbuffer;

        /* convert screen-coordinates to appropriate coordinates (and store them) */
        gp_stroke_convertcoords(p, &ptc->x, &pt->x, NULL);

        /* copy pressure */
        pt->pressure= ptc->pressure;
    }
    else {
        float *depth_arr= NULL;
        
        /* get an array of depths, far depths are blended */
        if (gpencil_project_check(p)) {
            int mval[2], mval_prev[2]= {0};
            int interp_depth = 0;
            int found_depth = 0;
            
            depth_arr= MEM_mallocN(sizeof(float) * gpd->sbuffer_size, "depth_points");

            for (i=0, ptc=gpd->sbuffer; i < gpd->sbuffer_size; i++, ptc++, pt++) {
                copy_v2_v2_int(mval, &ptc->x);

                if ((ED_view3d_autodist_depth(p->ar, mval, depth_margin, depth_arr+i) == 0) &&
                    (i && (ED_view3d_autodist_depth_seg(p->ar, mval, mval_prev, depth_margin + 1, depth_arr+i) == 0))
                ) {
                    interp_depth= TRUE;
                }
                else {
                    found_depth= TRUE;
                }

                copy_v2_v2_int(mval_prev, mval);
            }
            
            if (found_depth == FALSE) {
                /* eeh... not much we can do.. :/, ignore depth in this case, use the 3D cursor */
                for (i=gpd->sbuffer_size-1; i >= 0; i--)
                    depth_arr[i] = 0.9999f;
            }
            else {
                if (p->gpd->flag & GP_DATA_DEPTH_STROKE_ENDPOINTS) {
                    /* remove all info between the valid endpoints */
                    int first_valid = 0;
                    int last_valid = 0;
                    
                    for (i=0; i < gpd->sbuffer_size; i++) {
                        if (depth_arr[i] != FLT_MAX)
                            break;
                    }
                    first_valid= i;
                    
                    for (i=gpd->sbuffer_size-1; i >= 0; i--) {
                        if (depth_arr[i] != FLT_MAX)
                            break;
                    }
                    last_valid= i;
                    
                    /* invalidate non-endpoints, so only blend between first and last */
                    for (i=first_valid+1; i < last_valid; i++)
                        depth_arr[i]= FLT_MAX;
                    
                    interp_depth= TRUE;
                }
                
                if (interp_depth) {
                    interp_sparse_array(depth_arr, gpd->sbuffer_size, FLT_MAX);
                }
            }
        }
        
        
        pt= gps->points;
        
        /* convert all points (normal behaviour) */
        for (i=0, ptc=gpd->sbuffer; i < gpd->sbuffer_size && ptc; i++, ptc++, pt++) {
            /* convert screen-coordinates to appropriate coordinates (and store them) */
            gp_stroke_convertcoords(p, &ptc->x, &pt->x, depth_arr ? depth_arr+i:NULL);
            
            /* copy pressure */
            pt->pressure= ptc->pressure;
        }
        
        if (depth_arr)
            MEM_freeN(depth_arr);
    }
    
    p->flags |= GP_PAINTFLAG_STROKEADDED;

    /* add stroke to frame */
    BLI_addtail(&p->gpf->strokes, gps);
}

/* --- 'Eraser' for 'Paint' Tool ------ */

/* eraser tool - remove segment from stroke/split stroke (after lasso inside) */
static short gp_stroke_eraser_splitdel (bGPDframe *gpf, bGPDstroke *gps, int i)
{
    bGPDspoint *pt_tmp= gps->points;
    bGPDstroke *gsn = NULL;

    /* if stroke only had two points, get rid of stroke */
    if (gps->totpoints == 2) {
        /* free stroke points, then stroke */
        MEM_freeN(pt_tmp);
        BLI_freelinkN(&gpf->strokes, gps);
        
        /* nothing left in stroke, so stop */
        return 1;
    }

    /* if last segment, just remove segment from the stroke */
    else if (i == gps->totpoints - 2) {
        /* allocate new points array, and assign most of the old stroke there */
        gps->totpoints--;
        gps->points= MEM_callocN(sizeof(bGPDspoint)*gps->totpoints, "gp_stroke_points");
        memcpy(gps->points, pt_tmp, sizeof(bGPDspoint)*gps->totpoints);
        
        /* free temp buffer */
        MEM_freeN(pt_tmp);
        
        /* nothing left in stroke, so stop */
        return 1;
    }

    /* if first segment, just remove segment from the stroke */
    else if (i == 0) {
        /* allocate new points array, and assign most of the old stroke there */
        gps->totpoints--;
        gps->points= MEM_callocN(sizeof(bGPDspoint)*gps->totpoints, "gp_stroke_points");
        memcpy(gps->points, pt_tmp + 1, sizeof(bGPDspoint)*gps->totpoints);
        
        /* free temp buffer */
        MEM_freeN(pt_tmp);
        
        /* no break here, as there might still be stuff to remove in this stroke */
        return 0;
    }

    /* segment occurs in 'middle' of stroke, so split */
    else {
        /* duplicate stroke, and assign 'later' data to that stroke */
        gsn= MEM_dupallocN(gps);
        gsn->prev= gsn->next= NULL;
        BLI_insertlinkafter(&gpf->strokes, gps, gsn);
        
        gsn->totpoints= gps->totpoints - i;
        gsn->points= MEM_callocN(sizeof(bGPDspoint)*gsn->totpoints, "gp_stroke_points");
        memcpy(gsn->points, pt_tmp + i, sizeof(bGPDspoint)*gsn->totpoints);
        
        /* adjust existing stroke  */
        gps->totpoints= i;
        gps->points= MEM_callocN(sizeof(bGPDspoint)*gps->totpoints, "gp_stroke_points");
        memcpy(gps->points, pt_tmp, sizeof(bGPDspoint)*i);
        
        /* free temp buffer */
        MEM_freeN(pt_tmp);
        
        /* nothing left in stroke, so stop */
        return 1;
    }
}

/* eraser tool - check if part of stroke occurs within last segment drawn by eraser */
static short gp_stroke_eraser_strokeinside (int mval[], int UNUSED(mvalo[]), short rad, short x0, short y0, short x1, short y1)
{
    /* simple within-radius check for now */
    if (edge_inside_circle(mval[0], mval[1], rad, x0, y0, x1, y1))
        return 1;
    
    /* not inside */
    return 0;
} 

/* eraser tool - evaluation per stroke */
// TODO: this could really do with some optimisation (KD-Tree/BVH?)
static void gp_stroke_eraser_dostroke (tGPsdata *p, int mval[], int mvalo[], short rad, rcti *rect, bGPDframe *gpf, bGPDstroke *gps)
{
    bGPDspoint *pt1, *pt2;
    int x0=0, y0=0, x1=0, y1=0;
    int xyval[2];
    int i;
    
    if (gps->totpoints == 0) {
        /* just free stroke */
        if (gps->points) 
            MEM_freeN(gps->points);
        BLI_freelinkN(&gpf->strokes, gps);
    }
    else if (gps->totpoints == 1) {
        /* get coordinates */
        if (gps->flag & GP_STROKE_3DSPACE) {
            project_int(p->ar, &gps->points->x, xyval);
            x0= xyval[0];
            y0= xyval[1];
        }
        else if (gps->flag & GP_STROKE_2DSPACE) {           
            UI_view2d_view_to_region(p->v2d, gps->points->x, gps->points->y, &x0, &y0);
        }
#if 0
        else if (gps->flag & GP_STROKE_2DIMAGE) {           
            int offsx, offsy, sizex, sizey;
            
            /* get stored settings */
            sizex= p->im2d_settings.sizex;
            sizey= p->im2d_settings.sizey;
            offsx= p->im2d_settings.offsx;
            offsy= p->im2d_settings.offsy;
            
            /* calculate new points */
            x0= (int)((gps->points->x * sizex) + offsx);
            y0= (int)((gps->points->y * sizey) + offsy);
        }
#endif
        else {
            if (p->subrect == NULL) { /* normal 3D view */
                x0= (int)(gps->points->x / 100 * p->ar->winx);
                y0= (int)(gps->points->y / 100 * p->ar->winy);
            }
            else { /* camera view, use subrect */
                x0= (int)((gps->points->x / 100) * (p->subrect->xmax - p->subrect->xmin)) + p->subrect->xmin;
                y0= (int)((gps->points->y / 100) * (p->subrect->ymax - p->subrect->ymin)) + p->subrect->ymin;
            }
        }
        
        /* do boundbox check first */
        if (BLI_in_rcti(rect, x0, y0)) {
            /* only check if point is inside */
            if ( ((x0-mval[0])*(x0-mval[0]) + (y0-mval[1])*(y0-mval[1])) <= rad*rad ) {
                /* free stroke */
                MEM_freeN(gps->points);
                BLI_freelinkN(&gpf->strokes, gps);
            }
        }
    }
    else {  
        /* loop over the points in the stroke, checking for intersections 
         *  - an intersection will require the stroke to be split
         */
        for (i=0; (i+1) < gps->totpoints; i++) {
            /* get points to work with */
            pt1= gps->points + i;
            pt2= gps->points + i + 1;
            
            /* get coordinates */
            if (gps->flag & GP_STROKE_3DSPACE) {
                project_int(p->ar, &pt1->x, xyval);
                x0= xyval[0];
                y0= xyval[1];
                
                project_int(p->ar, &pt2->x, xyval);
                x1= xyval[0];
                y1= xyval[1];
            }
            else if (gps->flag & GP_STROKE_2DSPACE) {
                UI_view2d_view_to_region(p->v2d, pt1->x, pt1->y, &x0, &y0);
                
                UI_view2d_view_to_region(p->v2d, pt2->x, pt2->y, &x1, &y1);
            }
#if 0
            else if (gps->flag & GP_STROKE_2DIMAGE) {
                int offsx, offsy, sizex, sizey;
                
                /* get stored settings */
                sizex= p->im2d_settings.sizex;
                sizey= p->im2d_settings.sizey;
                offsx= p->im2d_settings.offsx;
                offsy= p->im2d_settings.offsy;
                
                /* calculate new points */
                x0= (int)((pt1->x * sizex) + offsx);
                y0= (int)((pt1->y * sizey) + offsy);
                
                x1= (int)((pt2->x * sizex) + offsx);
                y1= (int)((pt2->y * sizey) + offsy);
            }
#endif
            else {
                if(p->subrect == NULL) { /* normal 3D view */
                    x0= (int)(pt1->x / 100 * p->ar->winx);
                    y0= (int)(pt1->y / 100 * p->ar->winy);
                    x1= (int)(pt2->x / 100 * p->ar->winx);
                    y1= (int)(pt2->y / 100 * p->ar->winy);
                }
                else { /* camera view, use subrect */ 
                    x0= (int)((pt1->x / 100) * (p->subrect->xmax - p->subrect->xmin)) + p->subrect->xmin;
                    y0= (int)((pt1->y / 100) * (p->subrect->ymax - p->subrect->ymin)) + p->subrect->ymin;
                    x1= (int)((pt2->x / 100) * (p->subrect->xmax - p->subrect->xmin)) + p->subrect->xmin;
                    y1= (int)((pt2->y / 100) * (p->subrect->ymax - p->subrect->ymin)) + p->subrect->ymin;
                }
            }
            
            /* check that point segment of the boundbox of the eraser stroke */
            if (BLI_in_rcti(rect, x0, y0) || BLI_in_rcti(rect, x1, y1)) {
                /* check if point segment of stroke had anything to do with
                 * eraser region  (either within stroke painted, or on its lines)
                 *  - this assumes that linewidth is irrelevant
                 */
                if (gp_stroke_eraser_strokeinside(mval, mvalo, rad, x0, y0, x1, y1)) {
                    /* if function returns true, break this loop (as no more point to check) */
                    if (gp_stroke_eraser_splitdel(gpf, gps, i))
                        break;
                }
            }
        }
    }
}

/* erase strokes which fall under the eraser strokes */
static void gp_stroke_doeraser (tGPsdata *p)
{
    bGPDframe *gpf= p->gpf;
    bGPDstroke *gps, *gpn;
    rcti rect;
    
    /* rect is rectangle of eraser */
    rect.xmin= p->mval[0] - p->radius;
    rect.ymin= p->mval[1] - p->radius;
    rect.xmax= p->mval[0] + p->radius;
    rect.ymax= p->mval[1] + p->radius;
    
    /* loop over strokes, checking segments for intersections */
    for (gps= gpf->strokes.first; gps; gps= gpn) {
        gpn= gps->next;
        gp_stroke_eraser_dostroke(p, p->mval, p->mvalo, p->radius, &rect, gpf, gps);
    }
}

/* ******************************************* */
/* Sketching Operator */

/* clear the session buffers (call this before AND after a paint operation) */
static void gp_session_validatebuffer (tGPsdata *p)
{
    bGPdata *gpd= p->gpd;
    
    /* clear memory of buffer (or allocate it if starting a new session) */
    if (gpd->sbuffer) {
        //printf("\t\tGP - reset sbuffer\n");
        memset(gpd->sbuffer, 0, sizeof(tGPspoint)*GP_STROKE_BUFFER_MAX);
    }
    else {
        //printf("\t\tGP - allocate sbuffer\n");
        gpd->sbuffer= MEM_callocN(sizeof(tGPspoint)*GP_STROKE_BUFFER_MAX, "gp_session_strokebuffer");
    }
    
    /* reset indices */
    gpd->sbuffer_size = 0;
    
    /* reset flags */
    gpd->sbuffer_sflag= 0;
}

/* (re)init new painting data */
static int gp_session_initdata (bContext *C, tGPsdata *p)
{
    bGPdata **gpd_ptr = NULL;
    ScrArea *curarea= CTX_wm_area(C);
    ARegion *ar= CTX_wm_region(C);
    
    /* make sure the active view (at the starting time) is a 3d-view */
    if (curarea == NULL) {
        p->status= GP_STATUS_ERROR;
        if (G.f & G_DEBUG) 
            printf("Error: No active view for painting \n");
        return 0;
    }
    
    /* pass on current scene and window */
    p->scene= CTX_data_scene(C);
    p->win= CTX_wm_window(C);

    unit_m4(p->imat);
    
    switch (curarea->spacetype) {
        /* supported views first */
        case SPACE_VIEW3D:
        {
            // View3D *v3d= curarea->spacedata.first;
            // RegionView3D *rv3d= ar->regiondata;
            
            /* set current area 
             *  - must verify that region data is 3D-view (and not something else)
             */
            p->sa= curarea;
            p->ar= ar;
            
            if (ar->regiondata == NULL) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG)
                    printf("Error: 3D-View active region doesn't have any region data, so cannot be drawable \n");
                return 0;
            }

#if 0 // XXX will this sort of antiquated stuff be restored?
            /* check that gpencil data is allowed to be drawn */
            if ((v3d->flag2 & V3D_DISPGP)==0) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG) 
                    printf("Error: In active view, Grease Pencil not shown \n");
                return 0;
            }
#endif
        }
            break;

        case SPACE_NODE:
        {
            //SpaceNode *snode= curarea->spacedata.first;
            
            /* set current area */
            p->sa= curarea;
            p->ar= ar;
            p->v2d= &ar->v2d;
            
#if 0 // XXX will this sort of antiquated stuff be restored?
            /* check that gpencil data is allowed to be drawn */
            if ((snode->flag & SNODE_DISPGP)==0) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG) 
                    printf("Error: In active view, Grease Pencil not shown \n");
                return 0;
            }
#endif
        }
            break;
#if 0 // XXX these other spaces will come over time...
        case SPACE_SEQ:
        {
            SpaceSeq *sseq= curarea->spacedata.first;
            
            /* set current area */
            p->sa= curarea;
            p->ar= ar;
            p->v2d= &ar->v2d;
            
            /* check that gpencil data is allowed to be drawn */
            if (sseq->mainb == SEQ_DRAW_SEQUENCE) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG) 
                    printf("Error: In active view (sequencer), active mode doesn't support Grease Pencil \n");
                return 0;
            }
            if ((sseq->flag & SEQ_DRAW_GPENCIL)==0) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG) 
                    printf("Error: In active view, Grease Pencil not shown \n");
                return 0;
            }
        }
            break;  
#endif
        case SPACE_IMAGE:
        {
            //SpaceImage *sima= curarea->spacedata.first;
            
            /* set the current area */
            p->sa= curarea;
            p->ar= ar;
            p->v2d= &ar->v2d;
            //p->ibuf= BKE_image_get_ibuf(sima->image, &sima->iuser);
            
#if 0 // XXX disabled for now
            /* check that gpencil data is allowed to be drawn */
            if ((sima->flag & SI_DISPGP)==0) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG)
                    printf("Error: In active view, Grease Pencil not shown \n");
                return 0;
            }
#endif
        }
            break;
        case SPACE_CLIP:
        {
            SpaceClip *sc= curarea->spacedata.first;

            /* set the current area */
            p->sa= curarea;
            p->ar= ar;
            p->v2d= &ar->v2d;
            //p->ibuf= BKE_image_get_ibuf(sima->image, &sima->iuser);

            invert_m4_m4(p->imat, sc->unistabmat);

            /* custom color for new layer */
            p->custom_color[0]= 1.0f;
            p->custom_color[1]= 0.0f;
            p->custom_color[2]= 0.5f;
            p->custom_color[3]= 0.9f;

            /* check that gpencil data is allowed to be drawn */
            if ((sc->flag & SC_SHOW_GPENCIL)==0) {
                p->status= GP_STATUS_ERROR;
                if (G.f & G_DEBUG)
                    printf("Error: In active view, Grease Pencil not shown \n");
                return 0;
            }
        }
            break;

        /* unsupported views */
        default:
        {
            p->status= GP_STATUS_ERROR;
            if (G.f & G_DEBUG) 
                printf("Error: Active view not appropriate for Grease Pencil drawing \n");
            return 0;
        }
            break;
    }
    
    /* get gp-data */
    gpd_ptr= gpencil_data_get_pointers(C, &p->ownerPtr);
    if (gpd_ptr == NULL) {
        p->status= GP_STATUS_ERROR;
        if (G.f & G_DEBUG)
            printf("Error: Current context doesn't allow for any Grease Pencil data \n");
        return 0;
    }
    else {
        /* if no existing GPencil block exists, add one */
        if (*gpd_ptr == NULL)
            *gpd_ptr= gpencil_data_addnew("GPencil");
        p->gpd= *gpd_ptr;
    }
    
    if (ED_gpencil_session_active()==0) {
        /* initialize undo stack,
           also, existing undo stack would make buffer drawn */
        gpencil_undo_init(p->gpd);
    }
    
    /* clear out buffer (stored in gp-data), in case something contaminated it */
    gp_session_validatebuffer(p);
    
#if 0
    /* set 'default' im2d_settings just in case something that uses this doesn't set it */
    p->im2d_settings.sizex= 1;
    p->im2d_settings.sizey= 1;
#endif

    return 1;
}

/* init new painting session */
static tGPsdata *gp_session_initpaint (bContext *C)
{
    tGPsdata *p = NULL;

    /* create new context data */
    p= MEM_callocN(sizeof(tGPsdata), "GPencil Drawing Data");

    gp_session_initdata(C, p);
    
    /* return context data for running paint operator */
    return p;
}

/* cleanup after a painting session */
static void gp_session_cleanup (tGPsdata *p)
{
    bGPdata *gpd= (p) ? p->gpd : NULL;
    
    /* error checking */
    if (gpd == NULL)
        return;
    
    /* free stroke buffer */
    if (gpd->sbuffer) {
        //printf("\t\tGP - free sbuffer\n");
        MEM_freeN(gpd->sbuffer);
        gpd->sbuffer= NULL;
    }
    
    /* clear flags */
    gpd->sbuffer_size= 0;
    gpd->sbuffer_sflag= 0;
}

/* init new stroke */
static void gp_paint_initstroke (tGPsdata *p, short paintmode)
{   
    /* get active layer (or add a new one if non-existent) */
    p->gpl= gpencil_layer_getactive(p->gpd);
    if (p->gpl == NULL) {
        p->gpl= gpencil_layer_addnew(p->gpd);

        if(p->custom_color[3])
            copy_v3_v3(p->gpl->color, p->custom_color);
    }
    if (p->gpl->flag & GP_LAYER_LOCKED) {
        p->status= GP_STATUS_ERROR;
        if (G.f & G_DEBUG)
            printf("Error: Cannot paint on locked layer \n");
        return;
    }
        
    /* get active frame (add a new one if not matching frame) */
    p->gpf= gpencil_layer_getframe(p->gpl, p->scene->r.cfra, 1);
    if (p->gpf == NULL) {
        p->status= GP_STATUS_ERROR;
        if (G.f & G_DEBUG) 
            printf("Error: No frame created (gpencil_paint_init) \n");
        return;
    }
    else
        p->gpf->flag |= GP_FRAME_PAINT;
    
    /* set 'eraser' for this stroke if using eraser */
    p->paintmode= paintmode;
    if (p->paintmode == GP_PAINTMODE_ERASER)
        p->gpd->sbuffer_sflag |= GP_STROKE_ERASER;
        
    /* set 'initial run' flag, which is only used to denote when a new stroke is starting */
    p->flags |= GP_PAINTFLAG_FIRSTRUN;
    

    /* when drawing in the camera view, in 2D space, set the subrect */
    if (!(p->gpd->flag & GP_DATA_VIEWALIGN)) {
        if (p->sa->spacetype == SPACE_VIEW3D) {
            View3D *v3d= p->sa->spacedata.first;
            RegionView3D *rv3d= p->ar->regiondata;

            /* for camera view set the subrect */
            if (rv3d->persp == RV3D_CAMOB) {
                ED_view3d_calc_camera_border(p->scene, p->ar, v3d, rv3d, &p->subrect_data, TRUE); /* no shift */
                p->subrect= &p->subrect_data;
            }
        }
    }

    /* check if points will need to be made in view-aligned space */
    if (p->gpd->flag & GP_DATA_VIEWALIGN) {
        switch (p->sa->spacetype) {
            case SPACE_VIEW3D:
            {
                RegionView3D *rv3d= p->ar->regiondata;
                float rvec[3];
                
                /* get reference point for 3d space placement */
                gp_get_3d_reference(p, rvec);
                initgrabz(rv3d, rvec[0], rvec[1], rvec[2]);
                
                p->gpd->sbuffer_sflag |= GP_STROKE_3DSPACE;
            }
                break;
            
            case SPACE_NODE:
            {
                p->gpd->sbuffer_sflag |= GP_STROKE_2DSPACE;
            }
                break;
#if 0 // XXX other spacetypes to be restored in due course
            case SPACE_SEQ:
            {
                SpaceSeq *sseq= (SpaceSeq *)p->sa->spacedata.first;
                int rectx, recty;
                float zoom, zoomx, zoomy;
                
                /* set draw 2d-stroke flag */
                p->gpd->sbuffer_sflag |= GP_STROKE_2DIMAGE;
                
                /* calculate zoom factor */
                zoom= (float)(SEQ_ZOOM_FAC(sseq->zoom));
                if (sseq->mainb == SEQ_DRAW_IMG_IMBUF) {
                    zoomx = zoom * (p->scene->r.xasp / p->scene->r.yasp);
                    zoomy = zoom;
                } 
                else
                    zoomx = zoomy = zoom;
                
                /* calculate rect size to use to calculate the size of the drawing area
                 *  - We use the size of the output image not the size of the ibuf being shown
                 *    as it is too messy getting the ibuf (and could be too slow). This should be
                 *    a reasonable for most cases anyway.
                 */
                rectx= (p->scene->r.size * p->scene->r.xsch) / 100;
                recty= (p->scene->r.size * p->scene->r.ysch) / 100; 
                
                /* set offset and scale values for opertations to use */
                p->im2d_settings.sizex= (int)(zoomx * rectx);
                p->im2d_settings.sizey= (int)(zoomy * recty);
                p->im2d_settings.offsx= (int)((p->sa->winx-p->im2d_settings.sizex)/2 + sseq->xof);
                p->im2d_settings.offsy= (int)((p->sa->winy-p->im2d_settings.sizey)/2 + sseq->yof);
            }
                break;
#endif
            case SPACE_IMAGE:
            {
                SpaceImage *sima= (SpaceImage *)p->sa->spacedata.first;
                
                /* only set these flags if the image editor doesn't have an image active,
                 * otherwise user will be confused by strokes not appearing after they're drawn
                 *
                 * Admittedly, this is a bit hacky, but it works much nicer from an ergonomic standpoint!
                 */
                if ELEM(NULL, sima, sima->image) {
                    /* make strokes be drawn in screen space */
                    p->gpd->sbuffer_sflag &= ~GP_STROKE_2DSPACE;
                    p->gpd->flag &= ~GP_DATA_VIEWALIGN;
                }   
                else
                    p->gpd->sbuffer_sflag |= GP_STROKE_2DSPACE;
            }
                break;
                
            case SPACE_CLIP:
            {
                p->gpd->sbuffer_sflag |= GP_STROKE_2DSPACE;
            }
                break;
        }
    }
}

/* finish off a stroke (clears buffer, but doesn't finish the paint operation) */
static void gp_paint_strokeend (tGPsdata *p)
{
    /* for surface sketching, need to set the right OpenGL context stuff so that 
     * the conversions will project the values correctly...
     */
    if (gpencil_project_check(p)) {
        View3D *v3d= p->sa->spacedata.first;
        
        /* need to restore the original projection settings before packing up */
        view3d_region_operator_needs_opengl(p->win, p->ar);
        ED_view3d_autodist_init(p->scene, p->ar, v3d, (p->gpd->flag & GP_DATA_DEPTH_STROKE) ? 1:0);
    }
    
    /* check if doing eraser or not */
    if ((p->gpd->sbuffer_sflag & GP_STROKE_ERASER) == 0) {
        /* smooth stroke before transferring? */
        gp_stroke_smooth(p);
        
        /* simplify stroke before transferring? */
        gp_stroke_simplify(p);
        
        /* transfer stroke to frame */
        gp_stroke_newfrombuffer(p);
    }
    
    /* clean up buffer now */
    gp_session_validatebuffer(p);
}

/* finish off stroke painting operation */
static void gp_paint_cleanup (tGPsdata *p)
{
    /* p->gpd==NULL happens when stroke failed to initialize,
          for example. when GP is hidden in current space (sergey) */
    if (p->gpd) {
        /* finish off a stroke */
        gp_paint_strokeend(p);
    }
    
    /* "unlock" frame */
    if (p->gpf)
        p->gpf->flag &= ~GP_FRAME_PAINT;
}

/* ------------------------------- */

static void gpencil_draw_exit (bContext *C, wmOperator *op)
{
    tGPsdata *p= op->customdata;
    
    /* clear undo stack */
    gpencil_undo_finish();
    
    /* restore cursor to indicate end of drawing */
    WM_cursor_restore(CTX_wm_window(C));
    
    /* don't assume that operator data exists at all */
    if (p) {
        /* check size of buffer before cleanup, to determine if anything happened here */
        if (p->paintmode == GP_PAINTMODE_ERASER) {
            // TODO clear radial cursor thing
            // XXX draw_sel_circle(NULL, p.mvalo, 0, p.radius, 0);
        }
        
        /* cleanup */
        gp_paint_cleanup(p);
        gp_session_cleanup(p);
        
        /* finally, free the temp data */
        MEM_freeN(p);   
    }
    
    op->customdata= NULL;
}

static int gpencil_draw_cancel (bContext *C, wmOperator *op)
{
    /* this is just a wrapper around exit() */
    gpencil_draw_exit(C, op);
    return OPERATOR_CANCELLED;
}

/* ------------------------------- */


static int gpencil_draw_init (bContext *C, wmOperator *op)
{
    tGPsdata *p;
    int paintmode= RNA_enum_get(op->ptr, "mode");
    
    /* check context */
    p= op->customdata= gp_session_initpaint(C);
    if ((p == NULL) || (p->status == GP_STATUS_ERROR)) {
        /* something wasn't set correctly in context */
        gpencil_draw_exit(C, op);
        return 0;
    }
    
    /* init painting data */
    gp_paint_initstroke(p, paintmode);
    if (p->status == GP_STATUS_ERROR) {
        gpencil_draw_exit(C, op);
        return 0;
    }
    
    /* radius for eraser circle is defined in userprefs now */
    p->radius= U.gp_eraser;
    
    /* everything is now setup ok */
    return 1;
}

/* ------------------------------- */

/* update UI indicators of status, including cursor and header prints */
static void gpencil_draw_status_indicators (tGPsdata *p)
{
    /* header prints */
    switch (p->status) {
        case GP_STATUS_PAINTING:
            /* only print this for paint-sessions, otherwise it gets annoying */
            if (GPENCIL_SKETCH_SESSIONS_ON(p->scene))
                ED_area_headerprint(p->sa, "Grease Pencil: Drawing/erasing stroke... Release to end stroke");
            break;
        
        case GP_STATUS_IDLING:
            /* print status info */
            switch (p->paintmode) {
                case GP_PAINTMODE_ERASER:
                    ED_area_headerprint(p->sa, "Grease Pencil Erase Session: Hold and drag LMB or RMB to erase | ESC/Enter to end");
                    break;
                case GP_PAINTMODE_DRAW_STRAIGHT:
                    ED_area_headerprint(p->sa, "Grease Pencil Line Session: Hold and drag LMB to draw | ESC/Enter to end");
                    break;
                case GP_PAINTMODE_DRAW:
                    ED_area_headerprint(p->sa, "Grease Pencil Freehand Session: Hold and drag LMB to draw | ESC/Enter to end");
                    break;
                    
                default: /* unhandled future cases */
                    ED_area_headerprint(p->sa, "Grease Pencil Session: ESC/Enter to end");
                    break;
            }
            break;
            
        case GP_STATUS_ERROR:
        case GP_STATUS_DONE:
            /* clear status string */
            ED_area_headerprint(p->sa, NULL);
            break;
    }
}

/* ------------------------------- */

/* create a new stroke point at the point indicated by the painting context */
static void gpencil_draw_apply (wmOperator *op, tGPsdata *p)
{
    /* handle drawing/erasing -> test for erasing first */
    if (p->paintmode == GP_PAINTMODE_ERASER) {
        /* do 'live' erasing now */
        gp_stroke_doeraser(p);
        
        /* store used values */
        p->mvalo[0]= p->mval[0];
        p->mvalo[1]= p->mval[1];
        p->opressure= p->pressure;
    }
    /* only add current point to buffer if mouse moved (even though we got an event, it might be just noise) */
    else if (gp_stroke_filtermval(p, p->mval, p->mvalo)) {
        /* try to add point */
        short ok= gp_stroke_addpoint(p, p->mval, p->pressure);
        
        /* handle errors while adding point */
        if ((ok == GP_STROKEADD_FULL) || (ok == GP_STROKEADD_OVERFLOW)) {
            /* finish off old stroke */
            gp_paint_strokeend(p);
            
            /* start a new stroke, starting from previous point */
            gp_stroke_addpoint(p, p->mvalo, p->opressure);
            gp_stroke_addpoint(p, p->mval, p->pressure);
        }
        else if (ok == GP_STROKEADD_INVALID) {
            /* the painting operation cannot continue... */
            BKE_report(op->reports, RPT_ERROR, "Cannot paint stroke");
            p->status = GP_STATUS_ERROR;
            
            if (G.f & G_DEBUG) 
                printf("Error: Grease-Pencil Paint - Add Point Invalid \n");
            return;
        }
        
        /* store used values */
        p->mvalo[0]= p->mval[0];
        p->mvalo[1]= p->mval[1];
        p->opressure= p->pressure;
    }
}

/* handle draw event */
static void gpencil_draw_apply_event (wmOperator *op, wmEvent *event)
{
    tGPsdata *p= op->customdata;
    PointerRNA itemptr;
    float mousef[2];
    int tablet=0;

    /* convert from window-space to area-space mouse coordintes */
    // NOTE: float to ints conversions, +1 factor is probably used to ensure a bit more accurate rounding...
    p->mval[0]= event->mval[0] + 1;
    p->mval[1]= event->mval[1] + 1;

    /* handle pressure sensitivity (which is supplied by tablets) */
    if (event->custom == EVT_DATA_TABLET) {
        wmTabletData *wmtab= event->customdata;
        
        tablet= (wmtab->Active != EVT_TABLET_NONE);
        p->pressure= wmtab->Pressure;
        
        //if (wmtab->Active == EVT_TABLET_ERASER)
            // TODO... this should get caught by the keymaps which call drawing in the first place
    }
    else
        p->pressure= 1.0f;
    
    /* fill in stroke data (not actually used directly by gpencil_draw_apply) */
    RNA_collection_add(op->ptr, "stroke", &itemptr);
    
    mousef[0]= p->mval[0];
    mousef[1]= p->mval[1];
    RNA_float_set_array(&itemptr, "mouse", mousef);
    RNA_float_set(&itemptr, "pressure", p->pressure);
    RNA_boolean_set(&itemptr, "is_start", (p->flags & GP_PAINTFLAG_FIRSTRUN));
    
    /* special exception for start of strokes (i.e. maybe for just a dot) */
    if (p->flags & GP_PAINTFLAG_FIRSTRUN) {
        p->flags &= ~GP_PAINTFLAG_FIRSTRUN;
        
        p->mvalo[0]= p->mval[0];
        p->mvalo[1]= p->mval[1];
        p->opressure= p->pressure;
        
        /* special exception here for too high pressure values on first touch in
         *  windows for some tablets, then we just skip first touch ..  
         */
        if (tablet && (p->pressure >= 0.99f))
            return;
    }
    
    /* apply the current latest drawing point */
    gpencil_draw_apply(op, p);
    
    /* force refresh */
    ED_region_tag_redraw(p->ar); /* just active area for now, since doing whole screen is too slow */
}

/* ------------------------------- */

/* operator 'redo' (i.e. after changing some properties, but also for repeat last) */
static int gpencil_draw_exec (bContext *C, wmOperator *op)
{
    tGPsdata *p = NULL;
    
    //printf("GPencil - Starting Re-Drawing \n");
    
    /* try to initialise context data needed while drawing */
    if (!gpencil_draw_init(C, op)) {
        if (op->customdata) MEM_freeN(op->customdata);
        //printf("\tGP - no valid data \n");
        return OPERATOR_CANCELLED;
    }
    else
        p= op->customdata;
    
    //printf("\tGP - Start redrawing stroke \n");
    
    /* loop over the stroke RNA elements recorded (i.e. progress of mouse movement),
     * setting the relevant values in context at each step, then applying
     */
    RNA_BEGIN(op->ptr, itemptr, "stroke") 
    {
        float mousef[2];
        
        //printf("\t\tGP - stroke elem \n");
        
        /* get relevant data for this point from stroke */
        RNA_float_get_array(&itemptr, "mouse", mousef);
        p->mval[0] = (int)mousef[0];
        p->mval[1] = (int)mousef[1];
        p->pressure= RNA_float_get(&itemptr, "pressure");
        
        if (RNA_boolean_get(&itemptr, "is_start")) {
            /* if first-run flag isn't set already (i.e. not true first stroke),
             * then we must terminate the previous one first before continuing
             */
            if ((p->flags & GP_PAINTFLAG_FIRSTRUN) == 0) {
                // TODO: both of these ops can set error-status, but we probably don't need to worry
                gp_paint_strokeend(p);
                gp_paint_initstroke(p, p->paintmode);
            }
        }
        
        /* if first run, set previous data too */
        if (p->flags & GP_PAINTFLAG_FIRSTRUN) {
            p->flags &= ~GP_PAINTFLAG_FIRSTRUN;
            
            p->mvalo[0]= p->mval[0];
            p->mvalo[1]= p->mval[1];
            p->opressure= p->pressure;
        }
        
        /* apply this data as necessary now (as per usual) */
        gpencil_draw_apply(op, p);
    }
    RNA_END;
    
    //printf("\tGP - done \n");
    
    /* cleanup */
    gpencil_draw_exit(C, op);
    
    /* refreshes */
    WM_event_add_notifier(C, NC_SCREEN|ND_GPENCIL|NA_EDITED, NULL); // XXX need a nicer one that will work  
    
    /* done */
    return OPERATOR_FINISHED;
}

/* ------------------------------- */

/* start of interactive drawing part of operator */
static int gpencil_draw_invoke (bContext *C, wmOperator *op, wmEvent *event)
{
    tGPsdata *p = NULL;
    wmWindow *win= CTX_wm_window(C);
    
    if (G.f & G_DEBUG)
        printf("GPencil - Starting Drawing \n");
    
    /* try to initialise context data needed while drawing */
    if (!gpencil_draw_init(C, op)) {
        if (op->customdata) 
            MEM_freeN(op->customdata);
        if (G.f & G_DEBUG)
            printf("\tGP - no valid data \n");
        return OPERATOR_CANCELLED;
    }
    else
        p= op->customdata;
    
    // TODO: set any additional settings that we can take from the events?
    // TODO? if tablet is erasing, force eraser to be on?
    
    // TODO: move cursor setting stuff to stroke-start so that paintmode can be changed midway...
    
    /* if eraser is on, draw radial aid */
    if (p->paintmode == GP_PAINTMODE_ERASER) {
        // TODO: this involves mucking around with radial control, so we leave this for now..
    }
    
    /* set cursor */
    if (p->paintmode == GP_PAINTMODE_ERASER)
        WM_cursor_modal(win, BC_CROSSCURSOR); // XXX need a better cursor
    else
        WM_cursor_modal(win, BC_PAINTBRUSHCURSOR);
    
    /* special hack: if there was an initial event, then we were invoked via a hotkey, and 
     * painting should start immediately. Otherwise, this was called from a toolbar, in which
     * case we should wait for the mouse to be clicked.
     */
    if (event->type) {
        /* hotkey invoked - start drawing */
        //printf("\tGP - set first spot\n");
        p->status= GP_STATUS_PAINTING;
        
        /* handle the initial drawing - i.e. for just doing a simple dot */
        gpencil_draw_apply_event(op, event);
    }
    else {
        /* toolbar invoked - don't start drawing yet... */
        //printf("\tGP - hotkey invoked... waiting for click-drag\n");
    }
    
    WM_event_add_notifier(C, NC_SCREEN|ND_GPENCIL, NULL);
    /* add a modal handler for this operator, so that we can then draw continuous strokes */
    WM_event_add_modal_handler(C, op);
    return OPERATOR_RUNNING_MODAL;
}

/* gpencil modal operator stores area, which can be removed while using it (like fullscreen) */
static int gpencil_area_exists(bContext *C, ScrArea *satest)
{
    bScreen *sc= CTX_wm_screen(C);
    ScrArea *sa;
    
    for (sa= sc->areabase.first; sa; sa= sa->next) {
        if (sa==satest)
            return 1;
    }
    
    return 0;
}

static tGPsdata *gpencil_stroke_begin(bContext *C, wmOperator *op)
{
    tGPsdata *p= op->customdata;

    /* we must check that we're still within the area that we're set up to work from
     * otherwise we could crash (see bug #20586)
     */
    if (CTX_wm_area(C) != p->sa) {
        printf("\t\t\tGP - wrong area execution abort! \n");
        p->status= GP_STATUS_ERROR;
    }

    //printf("\t\tGP - start stroke \n");

    /* we may need to set up paint env again if we're resuming */
    // XXX: watch it with the paintmode! in future, it'd be nice to allow changing paint-mode when in sketching-sessions
    // XXX: with tablet events, we may event want to check for eraser here, for nicer tablet support

    if (gp_session_initdata(C, p))
        gp_paint_initstroke(p, p->paintmode);

    if(p->status != GP_STATUS_ERROR)
        p->status= GP_STATUS_PAINTING;

    return op->customdata;
}

static void gpencil_stroke_end(wmOperator *op)
{
    tGPsdata *p= op->customdata;

    gp_paint_cleanup(p);

    gpencil_undo_push(p->gpd);

    gp_session_cleanup(p);

    p->status= GP_STATUS_IDLING;

    p->gpd= NULL;
    p->gpl= NULL;
    p->gpf= NULL;
}

/* events handling during interactive drawing part of operator */
static int gpencil_draw_modal (bContext *C, wmOperator *op, wmEvent *event)
{
    tGPsdata *p= op->customdata;
    int estate = OPERATOR_PASS_THROUGH; /* default exit state - not handled, so let others have a share of the pie */
    
    // if (event->type == NDOF_MOTION)
    //  return OPERATOR_PASS_THROUGH;
    // -------------------------------
    // [mce] Not quite what I was looking
    // for, but a good start! GP continues to
    // draw on the screen while the 3D mouse
    // moves the viewpoint. Problem is that
    // the stroke is converted to 3D only after
    // it is finished. This approach should work
    // better in tools that immediately apply
    // in 3D space.

    //printf("\tGP - handle modal event...\n");
    
    /* exit painting mode (and/or end current stroke) */
    if (ELEM4(event->type, RETKEY, PADENTER, ESCKEY, SPACEKEY)) {
        /* exit() ends the current stroke before cleaning up */
        //printf("\t\tGP - end of paint op + end of stroke\n");
        p->status= GP_STATUS_DONE;
        estate = OPERATOR_FINISHED;
    }
    
    /* toggle painting mode upon mouse-button movement */
    if (ELEM(event->type, LEFTMOUSE, RIGHTMOUSE)) {
        /* if painting, end stroke */
        if (p->status == GP_STATUS_PAINTING) {
            int sketch= 0;
            /* basically, this should be mouse-button up = end stroke 
             * BUT what happens next depends on whether we 'painting sessions' is enabled
             */
            sketch |= GPENCIL_SKETCH_SESSIONS_ON(p->scene);
            /* polyline drawing is also 'sketching' -- all knots should be added during one session */
            sketch |= p->paintmode == GP_PAINTMODE_DRAW_POLY;

            if (sketch) {
                /* end stroke only, and then wait to resume painting soon */
                //printf("\t\tGP - end stroke only\n");
                gpencil_stroke_end(op);
                
                /* we've just entered idling state, so this event was processed (but no others yet) */
                estate = OPERATOR_RUNNING_MODAL;

                /* stroke could be smoothed, send notifier to refresh screen */
                WM_event_add_notifier(C, NC_SCREEN|ND_GPENCIL|NA_EDITED, NULL);
            }
            else {
                //printf("\t\tGP - end of stroke + op\n");
                p->status= GP_STATUS_DONE;
                estate = OPERATOR_FINISHED;
            }
        }
        else if (event->val == KM_PRESS) {
            /* not painting, so start stroke (this should be mouse-button down) */
            p= gpencil_stroke_begin(C, op);

            if (p->status == GP_STATUS_ERROR) {
                estate = OPERATOR_CANCELLED;
            }
        } 
        else {
            p->status = GP_STATUS_IDLING;
        }
    }
    
    /* handle mode-specific events */
    if (p->status == GP_STATUS_PAINTING) {
        /* handle painting mouse-movements? */
        if (ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE) || (p->flags & GP_PAINTFLAG_FIRSTRUN)) 
        {
            /* handle drawing event */
            //printf("\t\tGP - add point\n");
            gpencil_draw_apply_event(op, event);
            
            /* finish painting operation if anything went wrong just now */
            if (p->status == GP_STATUS_ERROR) {
                printf("\t\t\t\tGP - add error done! \n");
                estate = OPERATOR_CANCELLED;
            }
            else {
                /* event handled, so just tag as running modal */
                //printf("\t\t\t\tGP - add point handled!\n");
                estate = OPERATOR_RUNNING_MODAL;
            }
        }
        /* there shouldn't be any other events, but just in case there are, let's swallow them 
         * (i.e. to prevent problems with with undo)
         */
        else {
            /* swallow event to save ourselves trouble */
            estate = OPERATOR_RUNNING_MODAL;
        }
    }
    
    /* gpencil modal operator stores area, which can be removed while using it (like fullscreen) */
    if (0==gpencil_area_exists(C, p->sa))
        estate= OPERATOR_CANCELLED;
    else
        /* update status indicators - cursor, header, etc. */
        gpencil_draw_status_indicators(p);
    
    /* process last operations before exiting */
    switch (estate) {
        case OPERATOR_FINISHED:
            /* one last flush before we're done */
            gpencil_draw_exit(C, op);
            WM_event_add_notifier(C, NC_SCREEN|ND_GPENCIL|NA_EDITED, NULL); // XXX need a nicer one that will work
            break;
            
        case OPERATOR_CANCELLED:
            gpencil_draw_exit(C, op);
            break;

        case OPERATOR_RUNNING_MODAL|OPERATOR_PASS_THROUGH:
            /* event doesn't need to be handled */
            //printf("unhandled event -> %d (mmb? = %d | mmv? = %d)\n", event->type, event->type == MIDDLEMOUSE, event->type==MOUSEMOVE);
            break;
    }
    
    /* return status code */
    return estate;
}

/* ------------------------------- */

static EnumPropertyItem prop_gpencil_drawmodes[] = {
    {GP_PAINTMODE_DRAW, "DRAW", 0, "Draw Freehand", ""},
    {GP_PAINTMODE_DRAW_STRAIGHT, "DRAW_STRAIGHT", 0, "Draw Straight Lines", ""},
    {GP_PAINTMODE_DRAW_POLY, "DRAW_POLY", 0, "Draw Poly Line", ""},
    {GP_PAINTMODE_ERASER, "ERASER", 0, "Eraser", ""},
    {0, NULL, 0, NULL, NULL}
};

void GPENCIL_OT_draw (wmOperatorType *ot)
{
    /* identifiers */
    ot->name= "Grease Pencil Draw";
    ot->idname= "GPENCIL_OT_draw";
    ot->description= "Make annotations on the active data";
    
    /* api callbacks */
    ot->exec= gpencil_draw_exec;
    ot->invoke= gpencil_draw_invoke;
    ot->modal= gpencil_draw_modal;
    ot->cancel= gpencil_draw_cancel;
    ot->poll= gpencil_draw_poll;
    
    /* flags */
    ot->flag= OPTYPE_REGISTER|OPTYPE_UNDO|OPTYPE_BLOCKING;
    
    /* settings for drawing */
    RNA_def_enum(ot->srna, "mode", prop_gpencil_drawmodes, 0, "Mode", "Way to intepret mouse movements");
    
    RNA_def_collection_runtime(ot->srna, "stroke", &RNA_OperatorStrokeElement, "Stroke", "");
}