[gtk/wip/baedert/outline-radius: 2/2] css boxes: Compute box from border box

[Timm Bäder <baedert src gnome org>]

commit 39a42726bf7506820c34e94eea9a70a485586720
Author: Timm Bäder <mail baedert org>
Date:   Tue Feb 11 08:29:11 2020 +0100

    css boxes: Compute box from border box
    
    We can't just use the outline rect and apply the border radius because
    the outline box is the border box grown by the outline offset, which
    will also grow the resulting border radius.

 gtk/gtkcssboxesimplprivate.h | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)
---
diff --git a/gtk/gtkcssboxesimplprivate.h b/gtk/gtkcssboxesimplprivate.h
index 242ff5880c..a250de6212 100644
--- a/gtk/gtkcssboxesimplprivate.h
+++ b/gtk/gtkcssboxesimplprivate.h
@@ -471,16 +471,45 @@ gtk_css_boxes_compute_content_box (GtkCssBoxes *boxes)
 static inline void
 gtk_css_boxes_compute_outline_box (GtkCssBoxes *boxes)
 {
+  const GskRoundedRect *src;
+  GskRoundedRect *dest;
+  double d;
+  int i;
+
   if (boxes->has_box[GTK_CSS_AREA_OUTLINE_BOX])
     return;
 
-  gtk_css_boxes_compute_outline_rect (boxes);
+  gtk_css_boxes_compute_border_box (boxes);
 
-  gtk_css_boxes_apply_border_radius (&boxes->box[GTK_CSS_AREA_OUTLINE_BOX],
-                                     boxes->style->border->border_top_left_radius,
-                                     boxes->style->border->border_top_right_radius,
-                                     boxes->style->border->border_bottom_right_radius,
-                                     boxes->style->border->border_bottom_left_radius);
+  src = &boxes->box[GTK_CSS_AREA_BORDER_BOX];
+  dest = &boxes->box[GTK_CSS_AREA_OUTLINE_BOX];
+
+  d = _gtk_css_number_value_get (boxes->style->outline->outline_offset, 100) +
+      _gtk_css_number_value_get (boxes->style->outline->outline_width, 100);
+
+  /* Grow border rect into outline rect */
+  dest->bounds.origin.x = src->bounds.origin.x - d;
+  dest->bounds.origin.y = src->bounds.origin.y - d;
+  dest->bounds.size.width = src->bounds.size.width + d + d;
+  dest->bounds.size.height = src->bounds.size.height + d + d;
+
+  /* Grow corner radii of border rect */
+  for (i = 0; i < 4; i ++)
+    {
+      if (src->corner[i].width > 0) dest->corner[i].width = src->corner[i].width + d;
+      if (src->corner[i].height > 0) dest->corner[i].height = src->corner[i].height + d;
+
+      if (dest->corner[i].width <= 0 || dest->corner[i].height <= 0)
+        {
+          dest->corner[i].width = 0;
+          dest->corner[i].height = 0;
+        }
+      else
+        {
+          dest->corner[i].width = MIN (dest->corner[i].width, dest->bounds.size.width);
+          dest->corner[i].height = MIN (dest->corner[i].height, dest->bounds.size.height);
+        }
+    }
 
   boxes->has_box[GTK_CSS_AREA_OUTLINE_BOX] = TRUE;
 }