[gtk] cssshadowvalue: Simplify inset shadow nodes to color nodes if possible

[Timm Bäder <baedert src gnome org>]

commit a75523da68b838bf55d9f6f4d23eb2465ad3e68c
Author: Timm Bäder <mail baedert org>
Date:   Fri Nov 29 13:34:22 2019 +0100

    cssshadowvalue: Simplify inset shadow nodes to color nodes if possible
    
    inset shadows like this are frequently used to implement highlights in
    CSS without crowing them min size of the element.

 gtk/gtkcssshadowvalue.c | 81 +++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 71 insertions(+), 10 deletions(-)
---
diff --git a/gtk/gtkcssshadowvalue.c b/gtk/gtkcssshadowvalue.c
index d2febe7522..dc11a50367 100644
--- a/gtk/gtkcssshadowvalue.c
+++ b/gtk/gtkcssshadowvalue.c
@@ -386,23 +386,84 @@ gtk_css_shadow_value_snapshot_outset (const GtkCssValue    *shadow,
 }
 
 void
-gtk_css_shadow_value_snapshot_inset (const GtkCssValue   *shadow,
-                                     GtkSnapshot         *snapshot,
-                                     const GskRoundedRect*padding_box)
+gtk_css_shadow_value_snapshot_inset (const GtkCssValue    *shadow,
+                                     GtkSnapshot          *snapshot,
+                                     const GskRoundedRect *padding_box)
 {
+  double dx, dy, spread, radius;
+  const GdkRGBA *color;
+
   g_return_if_fail (shadow->class == &GTK_CSS_VALUE_SHADOW);
 
   /* We don't need to draw invisible shadows */
   if (gdk_rgba_is_clear (_gtk_css_rgba_value_get_rgba (shadow->color)))
     return;
 
-  gtk_snapshot_append_inset_shadow (snapshot,
-                                    padding_box, 
-                                    _gtk_css_rgba_value_get_rgba (shadow->color),
-                                    _gtk_css_number_value_get (shadow->hoffset, 0),
-                                    _gtk_css_number_value_get (shadow->voffset, 0),
-                                    _gtk_css_number_value_get (shadow->spread, 0),
-                                    _gtk_css_number_value_get (shadow->radius, 0));
+  dx = _gtk_css_number_value_get (shadow->hoffset, 0);
+  dy = _gtk_css_number_value_get (shadow->voffset, 0);
+  spread = _gtk_css_number_value_get (shadow->spread, 0);
+  radius = _gtk_css_number_value_get (shadow->radius, 0);
+  color = _gtk_css_rgba_value_get_rgba (shadow->color);
+
+  /* These are trivial to do with a color node */
+  if (spread == 0 && radius == 0 &&
+      gsk_rounded_rect_is_rectilinear (padding_box))
+    {
+      const graphene_rect_t *padding_bounds = &padding_box->bounds;
+
+      if (dx > 0)
+        {
+          const float y = dy > 0 ? dy : 0;
+
+          gtk_snapshot_append_color (snapshot, color,
+                                     &GRAPHENE_RECT_INIT (
+                                       padding_bounds->origin.x,
+                                       padding_bounds->origin.y + y,
+                                       dx,
+                                       padding_bounds->size.height - ABS (dy)
+                                     ));
+        }
+      else if (dx < 0)
+        {
+          const float y = dy > 0 ? dy : 0;
+
+          gtk_snapshot_append_color (snapshot, color,
+                                     &GRAPHENE_RECT_INIT (
+                                       padding_bounds->origin.x + padding_bounds->size.width + dx,
+                                       padding_bounds->origin.y + y,
+                                       - dx,
+                                       padding_bounds->size.height - ABS (dy)
+                                     ));
+        }
+
+      if (dy > 0)
+        {
+          gtk_snapshot_append_color (snapshot, color,
+                                     &GRAPHENE_RECT_INIT (
+                                       padding_bounds->origin.x,
+                                       padding_bounds->origin.y,
+                                       padding_bounds->size.width,
+                                       dy
+                                     ));
+        }
+      else if (dy < 0)
+        {
+          gtk_snapshot_append_color (snapshot, color,
+                                     &GRAPHENE_RECT_INIT (
+                                       padding_bounds->origin.x,
+                                       padding_bounds->origin.y + padding_bounds->size.height + dy,
+                                       padding_bounds->size.width,
+                                       - dy
+                                     ));
+        }
+    }
+  else
+    {
+      gtk_snapshot_append_inset_shadow (snapshot,
+                                        padding_box,
+                                        color,
+                                        dx, dy, spread, radius);
+    }
 }
 
 gboolean