GPencil: On the fly switching between Drawing and Erasing when using "Continuous Drawing"

It is now possible to switch between drawing and erasing strokes when in
the modal "Continous Drawing" sessions. This makes the drawing experience
just a little more fluid, saving some unncessary steps to get out of
the editing mode to activate the intended tool.

TODO: Is there interest for tablet support for this too?

1 files changed, 49 insertions, 1 deletions

diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index c03766a95e1..41caa777804 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -1236,6 +1236,16 @@ static void gp_paint_initstroke(tGPsdata *p, short paintmode)
 			}
 		}
 	}
+	else {
+		/* disable eraser flags - so that we can switch modes during a session */
+		p->gpd->sbuffer_sflag &= ~GP_STROKE_ERASER;
+		
+		if (p->sa->spacetype == SPACE_VIEW3D) {
+			if (p->gpl->flag & GP_LAYER_NO_XRAY) {
+				p->flags &= ~GP_PAINTFLAG_V3D_ERASER_DEPTH;
+			}
+		}
+	}
 	
 	/* set 'initial run' flag, which is only used to denote when a new stroke is starting */
 	p->flags |= GP_PAINTFLAG_FIRSTRUN;
@@ -1400,7 +1410,7 @@ static void gpencil_draw_toggle_eraser_cursor(bContext *C, tGPsdata *p, short en
 		WM_paint_cursor_end(CTX_wm_manager(C), p->erasercursor);
 		p->erasercursor = NULL;
 	}
-	else if (enable) {
+	else if (enable && !p->erasercursor) {
 		/* enable cursor */
 		p->erasercursor = WM_paint_cursor_activate(CTX_wm_manager(C),
 		                                           NULL, /* XXX */
@@ -1893,6 +1903,27 @@ static int gpencil_draw_modal(bContext *C, wmOperator *op, const wmEvent *event)
 				/* printf("\t\tGP - end stroke only\n"); */
 				gpencil_stroke_end(op);
 				
+				/* If eraser mode is on, turn it off after the stroke finishes
+				 * NOTE: This just makes it nicer to work with drawing sessions
+				 */
+				if (p->paintmode == GP_PAINTMODE_ERASER) {
+					p->paintmode = RNA_enum_get(op->ptr, "mode");
+					
+					/* if the original mode was *still* eraser,
+					 * we'll let it say for now, since this gives
+					 * users an opportunity to have visual feedback
+					 * when adjusting eraser size
+					 */
+					if (p->paintmode != GP_PAINTMODE_ERASER) {	
+						/* turn off cursor...
+						 * NOTE: this should be enough for now
+						 *       Just hiding this makes it seem like
+						 *       you can paint again...
+						 */
+						gpencil_draw_toggle_eraser_cursor(C, p, false);
+					}
+				}
+				
 				/* we've just entered idling state, so this event was processed (but no others yet) */
 				estate = OPERATOR_RUNNING_MODAL;
 				
@@ -1906,6 +1937,23 @@ static int gpencil_draw_modal(bContext *C, wmOperator *op, const wmEvent *event)
 			}
 		}
 		else if (event->val == KM_PRESS) {
+			/* Switch paintmode (temporarily if need be) based on which button was used
+			 * NOTE: This is to make it more convenient to erase strokes when using drawing sessions
+			 */
+			if (event->type == LEFTMOUSE) {
+				/* restore drawmode to default */
+				// XXX: no need for this... this should just revert by itself
+				if (p->paintmode == GP_PAINTMODE_ERASER)
+					gpencil_draw_toggle_eraser_cursor(C, p, false);
+					
+				p->paintmode = RNA_enum_get(op->ptr, "mode");
+			}
+			else if (event->type == RIGHTMOUSE) {
+				/* turn on eraser */
+				p->paintmode = GP_PAINTMODE_ERASER;
+				gpencil_draw_toggle_eraser_cursor(C, p, true);
+			}
+			
 			/* not painting, so start stroke (this should be mouse-button down) */
 			p = gpencil_stroke_begin(C, op);