Final fix (I hope!) for partial redraw.

The problem here is that the redraw rectangle can be calculated many
times before actual redraw (for instance due to repetitive calls to the
paint step function for space strokes). Those redraw rectangles need to
be accumulated and finally flushed when the draw call is done.

Also, it is this accumulated rectangle that must account for the
previously drawn rectangle to avoid artifacts due to drawing.

Now all looks like it works correctly :)

1 files changed, 29 insertions, 14 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index a04d4a36ee4..a60e3a806f1 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -511,6 +511,19 @@ static void sculpt_extend_redraw_rect_previous(Object *ob, rcti *rect)
 	}
 }
 
+static void sculpt_extend_redraw_rect_current(Object *ob, rcti *rect)
+{
+	/* redraw rectangles do not get flushed immediately. There may be many update steps
+	 * before a redraw is issued. All those need to be accumulated this happens in the current_r
+	 * which is finally united with the previous rectangle to get the final rectangle */
+	SculptSession *ss = ob->sculpt;
+
+	if (ss->cache) {
+		if (!BLI_rcti_is_empty(&ss->cache->current_r))
+			BLI_rcti_union(rect, &ss->cache->current_r);
+	}
+}
+
 /* Get a screen-space rectangle of the modified area */
 static int sculpt_get_redraw_rect(ARegion *ar, RegionView3D *rv3d,
                                   Object *ob, rcti *rect)
@@ -542,13 +555,20 @@ void sculpt_get_redraw_planes(float planes[4][4], ARegion *ar,
                               RegionView3D *rv3d, Object *ob)
 {
 	PBVH *pbvh = ob->sculpt->pbvh;
-	rcti rect;
+	/* copy here, original will be used below */
+	rcti rect = ob->sculpt->cache->current_r;
 
-	sculpt_get_redraw_rect(ar, rv3d, ob, &rect);
 	sculpt_extend_redraw_rect_previous(ob, &rect);
 
 	paint_calc_redraw_planes(planes, ar, rv3d, ob, &rect);
 
+	/* we will draw this rect, so now we can set it as the previous partial rect.
+	 * Note that we don't update with the union of previous/current (rect), only with
+	 * the current. Thus we avoid the rectangle needlessly growing to include
+	 * all the stroke area */
+	ob->sculpt->cache->previous_r = ob->sculpt->cache->current_r;
+	BLI_rcti_init(&ob->sculpt->cache->current_r, 0, 0, 0, 0);
+
 	/* clear redraw flag from nodes */
 	if (pbvh)
 		BKE_pbvh_update(pbvh, PBVH_UpdateRedraw, NULL);
@@ -4414,21 +4434,20 @@ static void sculpt_flush_update(bContext *C)
 		sculpt_update_object_bounding_box(ob);
 
 		if (sculpt_get_redraw_rect(ar, CTX_wm_region_view3d(C), ob, &r)) {
-			r.xmin -= 1;
-			r.xmax += 1;
-			r.ymin -= 1;
-			r.ymax += 1;
+			sculpt_extend_redraw_rect_current(ob, &r);
 
 			if (ss->cache) {
 				ss->cache->current_r = r;
 			}
 
+			/* previous is not set in the current cache else
+			 * the partial rect will always grow */
 			sculpt_extend_redraw_rect_previous(ob, &r);
 
-			r.xmin += ar->winrct.xmin;
-			r.xmax += ar->winrct.xmin;
-			r.ymin += ar->winrct.ymin;
-			r.ymax += ar->winrct.ymin;
+			r.xmin += ar->winrct.xmin - 2;
+			r.xmax += ar->winrct.xmin + 2;
+			r.ymin += ar->winrct.ymin - 2;
+			r.ymax += ar->winrct.ymin + 2;
 
 			ss->partial_redraw = 1;
 			ED_region_tag_redraw_partial(ar, &r);
@@ -4478,10 +4497,6 @@ static void sculpt_stroke_update_step(bContext *C, struct PaintStroke *UNUSED(st
 	SculptSession *ss = ob->sculpt;
 	const Brush *brush = BKE_paint_brush(&sd->paint);
 	
-	if (ss->cache) {
-		ss->cache->previous_r = ss->cache->current_r;
-	}
-
 	sculpt_stroke_modifiers_check(C, ob);
 	sculpt_update_cache_variants(C, sd, ob, itemptr);
 	sculpt_restore_mesh(sd, ob);