Grease Pencil Eraser - Numpad +/- and Scrollwheel Up/Down to change radius of

brush while erasing

This makes it easier to change the size of the brush without having to jump out
to the User Preferences and back

source/blender/editors/gpencil/gpencil_paint.c

@@ -1329,6 +1329,10 @@ static void gpencil_draw_exit(bContext *C, wmOperator *op)
 		if (p->paintmode == GP_PAINTMODE_ERASER) {
 			/* turn off radial brush cursor */
 			gpencil_draw_toggle_eraser_cursor(C, p, FALSE);
+			
+			/* if successful, store the new eraser size to be used again next time */
+			if (p->status == GP_STATUS_DONE)
+				U.gp_eraser = p->radius;
 		}
 		
 		/* cleanup */
@@ -1804,8 +1808,37 @@ static int gpencil_draw_modal(bContext *C, wmOperator *op, wmEvent *event)
 				estate = OPERATOR_RUNNING_MODAL;
 			}
 		}
+		/* eraser size */
+		else if ((p->paintmode == GP_PAINTMODE_ERASER) &&
+		         ELEM4(event->type, WHEELUPMOUSE, WHEELDOWNMOUSE, PADPLUSKEY, PADMINUS))
+		{
+			/* just resize the brush (local version)
+			 * TODO: fix the hardcoded size jumps (set to make a visible difference) and hardcoded keys
+			 */
+			//printf("\t\tGP - resize eraser\n");
+			switch (event->type) {
+				case WHEELUPMOUSE: /* larger */
+				case PADPLUSKEY:
+					p->radius += 5;
+					break;
+					
+				case WHEELDOWNMOUSE: /* smaller */
+				case PADMINUS:
+					p->radius -= 5;
+					
+					if (p->radius < 0) 
+						p->radius = 0;
+					break;
+			}
+			
+			/* force refresh */
+			ED_region_tag_redraw(p->ar); /* just active area for now, since doing whole screen is too slow */
+			
+			/* event handled, so just tag as running modal */
+			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)
+		 * (i.e. to prevent problems with undo)
 		 */
 		else {
 			/* swallow event to save ourselves trouble */