Merge branch 'master' into blender2.8

8 files changed, 199 insertions, 135 deletions

diff --git a/source/blender/editors/include/ED_screen.h b/source/blender/editors/include/ED_screen.h
index 89a6828a59d..942292788fc 100644
--- a/source/blender/editors/include/ED_screen.h
+++ b/source/blender/editors/include/ED_screen.h
@@ -125,7 +125,9 @@ int     ED_area_headersize(void);
 
 /* screens */
 void    ED_screens_initialize(struct wmWindowManager *wm);
-void    ED_screen_draw(struct wmWindow *win);
+void    ED_screen_draw_edges(struct wmWindow *win);
+void    ED_screen_draw_join_shape(struct ScrArea *sa1, struct ScrArea *sa2);
+void    ED_screen_draw_split_preview(struct ScrArea *sa, const int dir, const float fac);
 void    ED_screen_refresh(struct wmWindowManager *wm, struct wmWindow *win);
 void    ED_screen_do_listen(struct bContext *C, struct wmNotifier *note);
 bool    ED_screen_change(struct bContext *C, struct bScreen *sc);
diff --git a/source/blender/editors/screen/screen_draw.c b/source/blender/editors/screen/screen_draw.c
index 91b2be27d84..58dba662967 100644
--- a/source/blender/editors/screen/screen_draw.c
+++ b/source/blender/editors/screen/screen_draw.c
@@ -291,16 +291,13 @@ static void drawscredge_area(ScrArea *sa, int sizex, int sizey, unsigned int pos
 /**
  * Only for edge lines between areas, and the blended join arrows.
  */
-void ED_screen_draw(wmWindow *win)
+void ED_screen_draw_edges(wmWindow *win)
 {
 	bScreen *screen = WM_window_get_active_screen(win);
 	const int winsize_x = WM_window_pixels_x(win);
 	const int winsize_y = WM_window_pixels_y(win);
 
 	ScrArea *sa;
-	ScrArea *sa1 = NULL;
-	ScrArea *sa2 = NULL;
-	ScrArea *sa3 = NULL;
 
 	wmSubWindowSet(win, screen->mainwin);
 
@@ -323,36 +320,41 @@ void ED_screen_draw(wmWindow *win)
 
 	for (sa = screen->areabase.first; sa; sa = sa->next) {
 		drawscredge_area(sa, winsize_x, winsize_y, pos);
-
-		/* gather area split/join info */
-		if (sa->flag & AREA_FLAG_DRAWJOINFROM) sa1 = sa;
-		if (sa->flag & AREA_FLAG_DRAWJOINTO) sa2 = sa;
-		if (sa->flag & (AREA_FLAG_DRAWSPLIT_H | AREA_FLAG_DRAWSPLIT_V)) sa3 = sa;
 	}
 
+	immUnbindProgram();
+
+	screen->do_draw = false;
+}
+
+void ED_screen_draw_join_shape(ScrArea *sa1, ScrArea *sa2)
+{
+	unsigned int pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+	immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
+
+	glLineWidth(1);
+
 	/* blended join arrow */
-	if (sa1 && sa2) {
-		int dir = area_getorientation(sa1, sa2);
-		int dira = -1;
-		if (dir != -1) {
-			switch (dir) {
-				case 0: /* W */
-					dir = 'r';
-					dira = 'l';
-					break;
-				case 1: /* N */
-					dir = 'd';
-					dira = 'u';
-					break;
-				case 2: /* E */
-					dir = 'l';
-					dira = 'r';
-					break;
-				case 3: /* S */
-					dir = 'u';
-					dira = 'd';
-					break;
-			}
+	int dir = area_getorientation(sa1, sa2);
+	int dira = -1;
+	if (dir != -1) {
+		switch (dir) {
+			case 0: /* W */
+				dir = 'r';
+				dira = 'l';
+				break;
+			case 1: /* N */
+				dir = 'd';
+				dira = 'u';
+				break;
+			case 2: /* E */
+				dir = 'l';
+				dira = 'r';
+				break;
+			case 3: /* S */
+				dir = 'u';
+				dira = 'd';
+				break;
 		}
 
 		glEnable(GL_BLEND);
@@ -363,48 +365,59 @@ void ED_screen_draw(wmWindow *win)
 		glDisable(GL_BLEND);
 	}
 
-	/* splitpoint */
-	if (sa3) {
-		glEnable(GL_BLEND);
-		immUniformColor4ub(255, 255, 255, 100);
+	immUnbindProgram();
+}
 
-		immBegin(GWN_PRIM_LINES, 2);
+void ED_screen_draw_split_preview(ScrArea *sa, const int dir, const float fac)
+{
+	unsigned int pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
+	immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
 
-		if (sa3->flag & AREA_FLAG_DRAWSPLIT_H) {
-			immVertex2f(pos, sa3->totrct.xmin, win->eventstate->y);
-			immVertex2f(pos, sa3->totrct.xmax, win->eventstate->y);
+	/* splitpoint */
+	glEnable(GL_BLEND);
+	immUniformColor4ub(255, 255, 255, 100);
 
-			immEnd();
+	immBegin(GWN_PRIM_LINES, 2);
 
-			immUniformColor4ub(0, 0, 0, 100);
+	if (dir == 'h') {
+		const float y = (1 - fac) * sa->totrct.ymin + fac * sa->totrct.ymax;
 
-			immBegin(GWN_PRIM_LINES, 2);
+		immVertex2f(pos, sa->totrct.xmin, y);
+		immVertex2f(pos, sa->totrct.xmax, y);
 
-			immVertex2f(pos, sa3->totrct.xmin, win->eventstate->y + 1);
-			immVertex2f(pos, sa3->totrct.xmax, win->eventstate->y + 1);
-		}
-		else {
-			immVertex2f(pos, win->eventstate->x, sa3->totrct.ymin);
-			immVertex2f(pos, win->eventstate->x, sa3->totrct.ymax);
+		immEnd();
+
+		immUniformColor4ub(0, 0, 0, 100);
 
-			immEnd();
+		immBegin(GWN_PRIM_LINES, 2);
 
-			immUniformColor4ub(0, 0, 0, 100);
+		immVertex2f(pos, sa->totrct.xmin, y + 1);
+		immVertex2f(pos, sa->totrct.xmax, y + 1);
 
-			immBegin(GWN_PRIM_LINES, 2);
+		immEnd();
+	}
+	else {
+		BLI_assert(dir == 'v');
+		const float x = (1 - fac) * sa->totrct.xmin + fac * sa->totrct.xmax;
 
-			immVertex2f(pos, win->eventstate->x + 1, sa3->totrct.ymin);
-			immVertex2f(pos, win->eventstate->x + 1, sa3->totrct.ymax);
-		}
+		immVertex2f(pos, x, sa->totrct.ymin);
+		immVertex2f(pos, x, sa->totrct.ymax);
 
 		immEnd();
 
-		glDisable(GL_BLEND);
+		immUniformColor4ub(0, 0, 0, 100);
+
+		immBegin(GWN_PRIM_LINES, 2);
+
+		immVertex2f(pos, x + 1, sa->totrct.ymin);
+		immVertex2f(pos, x + 1, sa->totrct.ymax);
+
+		immEnd();
 	}
 
-	immUnbindProgram();
+	glDisable(GL_BLEND);
 
-	screen->do_draw = false;
+	immUnbindProgram();
 }
 
 
diff --git a/source/blender/editors/screen/screen_edit.c b/source/blender/editors/screen/screen_edit.c
index d3f99dc8152..0b78590d4d8 100644
--- a/source/blender/editors/screen/screen_edit.c
+++ b/source/blender/editors/screen/screen_edit.c
@@ -589,8 +589,6 @@ int screen_area_join(bContext *C, bScreen *scr, ScrArea *sa1, ScrArea *sa2)
 	/*printf("dir is : %i\n", dir);*/
 	
 	if (dir == -1) {
-		if (sa1) sa1->flag &= ~AREA_FLAG_DRAWJOINFROM;
-		if (sa2) sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
 		return 0;
 	}
 	
@@ -621,7 +619,7 @@ int screen_area_join(bContext *C, bScreen *scr, ScrArea *sa1, ScrArea *sa2)
 	
 	screen_delarea(C, scr, sa2);
 	removedouble_scrverts(scr);
-	sa1->flag &= ~AREA_FLAG_DRAWJOINFROM;
+
 	/* Update preview thumbnail */
 	BKE_icon_changed(scr->id.icon_id);
 
diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index 39b1f5ff5dd..3f52d232a39 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -1197,18 +1197,15 @@ static int area_snap_calc_location(
 
 	const int m_loc = origval + delta;
 	const int axis = (dir == 'v') ? 0 : 1;
-	int snap_dist = INT_MAX;
+	int snap_dist;
 	int dist;
 	{
 		/* Test the snap to middle. */
 		int middle = origval + (bigger - smaller) / 2;
 		middle -= (middle % AREAGRID);
 
-		dist = abs(m_loc - middle);
-		if (dist <= snap_dist) {
-			snap_dist = dist;
-			final_loc = middle;
-		}
+		snap_dist = abs(m_loc - middle);
+		final_loc = middle;
 	}
 
 	for (const ScrVert *v1 = sc->vertbase.first; v1; v1 = v1->next) {
@@ -1452,6 +1449,7 @@ typedef struct sAreaSplitData {
 	int delta;              /* delta move edge */
 	int origmin, origsize;  /* to calculate fac, for property storage */
 	int previewmode;        /* draw previewline, then split */
+	void *draw_callback;    /* call `ED_screen_draw_split_preview` */
 	bool do_snap;
 
 	ScrEdge *nedge;         /* new edge */
@@ -1460,6 +1458,19 @@ typedef struct sAreaSplitData {
 	
 } sAreaSplitData;
 
+static void area_split_draw_cb(const struct wmWindow *UNUSED(win), void *userdata)
+{
+	const wmOperator *op = userdata;
+
+	sAreaSplitData *sd = op->customdata;
+	if (sd->sarea) {
+		int dir = RNA_enum_get(op->ptr, "direction");
+		float fac = RNA_float_get(op->ptr, "factor");
+
+		ED_screen_draw_split_preview(sd->sarea, dir, fac);
+	}
+}
+
 /* generic init, menu case, doesn't need active area */
 static int area_split_menu_init(bContext *C, wmOperator *op)
 {
@@ -1470,15 +1481,7 @@ static int area_split_menu_init(bContext *C, wmOperator *op)
 	op->customdata = sd;
 	
 	sd->sarea = CTX_wm_area(C);
-	
-	if (sd->sarea) {
-		int dir = RNA_enum_get(op->ptr, "direction");
 
-		if (dir == 'h')
-			sd->sarea->flag |= AREA_FLAG_DRAWSPLIT_H;
-		else
-			sd->sarea->flag |= AREA_FLAG_DRAWSPLIT_V;
-	}
 	return 1;
 }
 
@@ -1589,9 +1592,9 @@ static void area_split_exit(bContext *C, wmOperator *op)
 		if (sd->sarea) ED_area_tag_redraw(sd->sarea);
 		if (sd->narea) ED_area_tag_redraw(sd->narea);
 
-		if (sd->sarea)
-			sd->sarea->flag &= ~(AREA_FLAG_DRAWSPLIT_H | AREA_FLAG_DRAWSPLIT_V);
-		
+		if (sd->draw_callback)
+			WM_draw_cb_exit(CTX_wm_window(C), sd->draw_callback);
+
 		MEM_freeN(op->customdata);
 		op->customdata = NULL;
 	}
@@ -1698,6 +1701,7 @@ static int area_split_invoke(bContext *C, wmOperator *op, const wmEvent *event)
 	}
 	else {
 		sd->previewmode = 1;
+		sd->draw_callback = WM_draw_cb_activate(win, area_split_draw_cb, op);
 		/* add temp handler for edge move or cancel */
 		WM_event_add_modal_handler(C, op);
 		
@@ -1755,9 +1759,7 @@ static int area_split_modal(bContext *C, wmOperator *op, const wmEvent *event)
 			if (sd->previewmode == 0)
 				area_move_apply_do(C, sd->delta, sd->origval, dir, sd->bigger, sd->smaller, sd->do_snap);
 			else {
-				/* TODO: Snap in preview mode too. */
 				if (sd->sarea) {
-					sd->sarea->flag &= ~(AREA_FLAG_DRAWSPLIT_H | AREA_FLAG_DRAWSPLIT_V);
 					ED_area_tag_redraw(sd->sarea);
 				}
 				/* area context not set */
@@ -1768,22 +1770,31 @@ static int area_split_modal(bContext *C, wmOperator *op, const wmEvent *event)
 					if (dir == 'v') {
 						sd->origsize = sd->sarea->winx;
 						sd->origmin = sd->sarea->totrct.xmin;
-						sd->sarea->flag |= AREA_FLAG_DRAWSPLIT_V;
 					}
 					else {
 						sd->origsize = sd->sarea->winy;
 						sd->origmin = sd->sarea->totrct.ymin;
-						sd->sarea->flag |= AREA_FLAG_DRAWSPLIT_H;
 					}
+
+					if (sd->do_snap) {
+						ScrArea *sa = sd->sarea;
+						sa->v1->editflag = sa->v2->editflag = sa->v3->editflag = sa->v4->editflag = 1;
+
+						int snap_loc = area_snap_calc_location(
+						        CTX_wm_screen(C), sd->delta, sd->origval, dir, sd->origmin + sd->origsize, -sd->origmin);
+
+						sa->v1->editflag = sa->v2->editflag = sa->v3->editflag = sa->v4->editflag = 0;
+						fac = snap_loc - sd->origmin;
+					}
+					else {
+						fac = (dir == 'v') ? event->x - sd->origmin : event->y - sd->origmin;
+					}
+					RNA_float_set(op->ptr, "factor", fac / (float)sd->origsize);
 				}
-				
+
 				CTX_wm_screen(C)->do_draw = true;
 
 			}
-			
-			fac = (dir == 'v') ? event->x - sd->origmin : event->y - sd->origmin;
-			RNA_float_set(op->ptr, "factor", fac / (float)sd->origsize);
-			
 			break;
 			
 		case LEFTMOUSE:
@@ -1809,19 +1820,14 @@ static int area_split_modal(bContext *C, wmOperator *op, const wmEvent *event)
 				
 				if (event->val == KM_PRESS) {
 					if (sd->sarea) {
-						sd->sarea->flag &= ~(AREA_FLAG_DRAWSPLIT_H | AREA_FLAG_DRAWSPLIT_V);
 						ED_area_tag_redraw(sd->sarea);
 						
 						if (dir == 'v') {
 							RNA_enum_set(op->ptr, "direction", 'h');
-							sd->sarea->flag |= AREA_FLAG_DRAWSPLIT_H;
-							
 							WM_cursor_set(CTX_wm_window(C), CURSOR_X_MOVE);
 						}
 						else {
 							RNA_enum_set(op->ptr, "direction", 'v');
-							sd->sarea->flag |= AREA_FLAG_DRAWSPLIT_V;
-							
 							WM_cursor_set(CTX_wm_window(C), CURSOR_Y_MOVE);
 						}
 					}
@@ -2562,13 +2568,23 @@ static void SCREEN_OT_screen_full_area(wmOperatorType *ot)
  */
 
 typedef struct sAreaJoinData {
-	ScrArea *sa1;   /* first area to be considered */
-	ScrArea *sa2;   /* second area to be considered */
-	ScrArea *scr;   /* designed for removal */
+	ScrArea *sa1;        /* first area to be considered */
+	ScrArea *sa2;        /* second area to be considered */
+	void *draw_callback; /* call `ED_screen_draw_join_shape` */
 
 } sAreaJoinData;
 
 
+static void area_join_draw_cb(const struct wmWindow *UNUSED(win), void *userdata)
+{
+	const wmOperator *op = userdata;
+
+	sAreaJoinData *sd = op->customdata;
+	if (sd->sa1 && sd->sa2) {
+		ED_screen_draw_join_shape(sd->sa1, sd->sa2);
+	}
+}
+
 /* validate selection inside screen, set variables OK */
 /* return 0: init failed */
 /* XXX todo: find edge based on (x,y) and set other area? */
@@ -2602,14 +2618,14 @@ static int area_join_init(bContext *C, wmOperator *op)
 	}
 	
 	jd = (sAreaJoinData *)MEM_callocN(sizeof(sAreaJoinData), "op_area_join");
-	
+
 	jd->sa1 = sa1;
-	jd->sa1->flag |= AREA_FLAG_DRAWJOINFROM;
 	jd->sa2 = sa2;
-	jd->sa2->flag |= AREA_FLAG_DRAWJOINTO;
-	
+
 	op->customdata = jd;
-	
+
+	jd->draw_callback = WM_draw_cb_activate(CTX_wm_window(C), area_join_draw_cb, op);
+
 	return 1;
 }
 
@@ -2633,8 +2649,13 @@ static int area_join_apply(bContext *C, wmOperator *op)
 /* finish operation */
 static void area_join_exit(bContext *C, wmOperator *op)
 {
-	if (op->customdata) {
-		MEM_freeN(op->customdata);
+	sAreaJoinData *jd = (sAreaJoinData *)op->customdata;
+
+	if (jd) {
+		if (jd->draw_callback)
+			WM_draw_cb_exit(CTX_wm_window(C), jd->draw_callback);
+
+		MEM_freeN(jd);
 		op->customdata = NULL;
 	}
 	
@@ -2693,17 +2714,6 @@ static int area_join_invoke(bContext *C, wmOperator *op, const wmEvent *event)
 
 static void area_join_cancel(bContext *C, wmOperator *op)
 {
-	sAreaJoinData *jd = (sAreaJoinData *)op->customdata;
-	
-	if (jd->sa1) {
-		jd->sa1->flag &= ~AREA_FLAG_DRAWJOINFROM;
-		jd->sa1->flag &= ~AREA_FLAG_DRAWJOINTO;
-	}
-	if (jd->sa2) {
-		jd->sa2->flag &= ~AREA_FLAG_DRAWJOINFROM;
-		jd->sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
-	}
-	
 	WM_event_add_notifier(C, NC_WINDOW, NULL);
 	
 	area_join_exit(C, op);
@@ -2727,9 +2737,7 @@ static int area_join_modal(bContext *C, wmOperator *op, const wmEvent *event)
 				if (jd->sa1 != sa) {
 					dir = area_getorientation(jd->sa1, sa);
 					if (dir != -1) {
-						if (jd->sa2) jd->sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
 						jd->sa2 = sa;
-						jd->sa2->flag |= AREA_FLAG_DRAWJOINTO;
 					}
 					else {
 						/* we are not bordering on the previously selected area 
@@ -2738,15 +2746,10 @@ static int area_join_modal(bContext *C, wmOperator *op, const wmEvent *event)
 						 */
 						dir = area_getorientation(sa, jd->sa2);
 						if (dir != -1) {
-							if (jd->sa1) jd->sa1->flag &= ~AREA_FLAG_DRAWJOINFROM;
-							if (jd->sa2) jd->sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
 							jd->sa1 = jd->sa2;
 							jd->sa2 = sa;
-							if (jd->sa1) jd->sa1->flag |= AREA_FLAG_DRAWJOINFROM;
-							if (jd->sa2) jd->sa2->flag |= AREA_FLAG_DRAWJOINTO;
 						}
 						else {
-							if (jd->sa2) jd->sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
 							jd->sa2 = NULL;
 						}
 					}
@@ -2756,12 +2759,8 @@ static int area_join_modal(bContext *C, wmOperator *op, const wmEvent *event)
 					/* we are back in the area previously selected for keeping 
 					 * we swap the areas if possible to allow user to choose */
 					if (jd->sa2 != NULL) {
-						if (jd->sa1) jd->sa1->flag &= ~AREA_FLAG_DRAWJOINFROM;
-						if (jd->sa2) jd->sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
 						jd->sa1 = jd->sa2;
 						jd->sa2 = sa;
-						if (jd->sa1) jd->sa1->flag |= AREA_FLAG_DRAWJOINFROM;
-						if (jd->sa2) jd->sa2->flag |= AREA_FLAG_DRAWJOINTO;
 						dir = area_getorientation(jd->sa1, jd->sa2);
 						if (dir == -1) {
 							printf("oops, didn't expect that!\n");
@@ -2770,9 +2769,7 @@ static int area_join_modal(bContext *C, wmOperator *op, const wmEvent *event)
 					else {
 						dir = area_getorientation(jd->sa1, sa);
 						if (dir != -1) {
-							if (jd->sa2) jd->sa2->flag &= ~AREA_FLAG_DRAWJOINTO;
 							jd->sa2 = sa;
-							jd->sa2->flag |= AREA_FLAG_DRAWJOINTO;
 						}
 					}
 					WM_event_add_notifier(C, NC_WINDOW, NULL);
diff --git a/source/blender/makesdna/DNA_screen_types.h b/source/blender/makesdna/DNA_screen_types.h
index e3e5aaf8ca4..dd716014f66 100644
--- a/source/blender/makesdna/DNA_screen_types.h
+++ b/source/blender/makesdna/DNA_screen_types.h
@@ -290,11 +290,11 @@ typedef struct ARegion {
 /* area->flag */
 enum {
 	HEADER_NO_PULLDOWN           = (1 << 0),
-	AREA_FLAG_DRAWJOINTO         = (1 << 1),
-	AREA_FLAG_DRAWJOINFROM       = (1 << 2),
+//	AREA_FLAG_DEPRECATED_1       = (1 << 1),
+//	AREA_FLAG_DEPRECATED_2       = (1 << 2),
 	AREA_TEMP_INFO               = (1 << 3),
-	AREA_FLAG_DRAWSPLIT_H        = (1 << 4),
-	AREA_FLAG_DRAWSPLIT_V        = (1 << 5),
+//	AREA_FLAG_DEPRECATED_4       = (1 << 4),
+//	AREA_FLAG_DEPRECATED_5       = (1 << 5),
 	/* used to check if we should switch back to prevspace (of a different type) */
 	AREA_FLAG_TEMP_TYPE          = (1 << 6),
 	/* for temporary fullscreens (file browser, image editor render) that are opened above user set fullscreens */
diff --git a/source/blender/makesdna/DNA_windowmanager_types.h b/source/blender/makesdna/DNA_windowmanager_types.h
index fd2a422b4c8..f794c5cbaff 100644
--- a/source/blender/makesdna/DNA_windowmanager_types.h
+++ b/source/blender/makesdna/DNA_windowmanager_types.h
@@ -227,6 +227,9 @@ typedef struct wmWindow {
 	ListBase gesture;             /* gesture stuff */
 
 	struct Stereo3dFormat *stereo3d_format; /* properties for stereoscopic displays */
+
+	/* custom drawing callbacks */
+	ListBase drawcalls;
 } wmWindow;
 
 #ifdef ime_data
diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index e3f53e4b5cb..85f94721d40 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -539,6 +539,11 @@ void		WM_progress_set(struct wmWindow *win, float progress);
 void		WM_progress_clear(struct wmWindow *win);
 
 			/* Draw (for screenshot) */
+void        *WM_draw_cb_activate(
+                    struct wmWindow *win,
+                    void (*draw)(const struct wmWindow *, void *),
+                    void *customdata);
+void        WM_draw_cb_exit(struct wmWindow *win, void *handle);
 void		WM_redraw_windows(struct bContext *C);
 
 void        WM_main_playanim(int argc, const char **argv);
diff --git a/source/blender/windowmanager/intern/wm_draw.c b/source/blender/windowmanager/intern/wm_draw.c
index c6b25ff8079..92bb81d2221 100644
--- a/source/blender/windowmanager/intern/wm_draw.c
+++ b/source/blender/windowmanager/intern/wm_draw.c
@@ -162,6 +162,46 @@ static void wm_region_test_render_do_draw(const Scene *scene, ScrArea *sa, ARegi
 /********************** draw all **************************/
 /* - reference method, draw all each time                 */
 
+typedef struct WindowDrawCB {
+	struct WindowDrawCB *next, *prev;
+
+	void(*draw)(const struct wmWindow *, void *);
+	void *customdata;
+
+} WindowDrawCB;
+
+void *WM_draw_cb_activate(
+        wmWindow *win,
+        void(*draw)(const struct wmWindow *, void *),
+        void *customdata)
+{
+	WindowDrawCB *wdc = MEM_callocN(sizeof(*wdc), "WindowDrawCB");
+
+	BLI_addtail(&win->drawcalls, wdc);
+	wdc->draw = draw;
+	wdc->customdata = customdata;
+
+	return wdc;
+}
+
+void WM_draw_cb_exit(wmWindow *win, void *handle)
+{
+	for (WindowDrawCB *wdc = win->drawcalls.first; wdc; wdc = wdc->next) {
+		if (wdc == (WindowDrawCB *)handle) {
+			BLI_remlink(&win->drawcalls, wdc);
+			MEM_freeN(wdc);
+			return;
+		}
+	}
+}
+
+static void wm_draw_callbacks(wmWindow *win)
+{
+	for (WindowDrawCB *wdc = win->drawcalls.first; wdc; wdc = wdc->next) {
+		wdc->draw(win, wdc->customdata);
+	}
+}
+
 static void wm_method_draw_full(bContext *C, wmWindow *win)
 {
 	bScreen *screen = WM_window_get_active_screen(win);
@@ -186,8 +226,9 @@ static void wm_method_draw_full(bContext *C, wmWindow *win)
 		CTX_wm_area_set(C, NULL);
 	}
 
-	ED_screen_draw(win);
+	ED_screen_draw_edges(win);
 	screen->do_draw = false;
+	wm_draw_callbacks(win);
 
 	/* draw overlapping regions */
 	for (ar = screen->regionbase.first; ar; ar = ar->next) {
@@ -323,17 +364,19 @@ static void wm_method_draw_overlap_all(bContext *C, wmWindow *win, int exchange)
 
 	/* after area regions so we can do area 'overlay' drawing */
 	if (screen->do_draw) {
-		ED_screen_draw(win);
+		ED_screen_draw_edges(win);
 		screen->do_draw = false;
+		wm_draw_callbacks(win);
 
 		if (exchange)
 			screen->swap = WIN_FRONT_OK;
 	}
 	else if (exchange) {
 		if (screen->swap == WIN_FRONT_OK) {
-			ED_screen_draw(win);
+			ED_screen_draw_edges(win);
 			screen->do_draw = false;
 			screen->swap = WIN_BOTH_OK;
+			wm_draw_callbacks(win);
 		}
 		else if (screen->swap == WIN_BACK_OK)
 			screen->swap = WIN_FRONT_OK;
@@ -627,8 +670,9 @@ static void wm_method_draw_triple(bContext *C, wmWindow *win)
 	}
 
 	/* after area regions so we can do area 'overlay' drawing */
-	ED_screen_draw(win);
+	ED_screen_draw_edges(win);
 	WM_window_get_active_screen(win)->do_draw = false;
+	wm_draw_callbacks(win);
 
 	/* draw floating regions (menus) */
 	for (ar = screen->regionbase.first; ar; ar = ar->next) {
@@ -802,10 +846,12 @@ static void wm_method_draw_triple_multiview(bContext *C, wmWindow *win, eStereoV
 	}
 
 	/* after area regions so we can do area 'overlay' drawing */
-	ED_screen_draw(win);
+	ED_screen_draw_edges(win);
 	if (sview == STEREO_RIGHT_ID)
 		screen->do_draw = false;
 
+	wm_draw_callbacks(win);
+
 	/* draw floating regions (menus) */
 	for (ar = screen->regionbase.first; ar; ar = ar->next) {
 		if (ar->swinid) {