[gnome-shell] panelCorner: Only overlap panel if necessary

[Florian MÃllner <fmuellner src gnome org>]

commit a112bfdaa2c30fdc118cea92ddfe435ab1f21e6a
Author: Florian MÃllner <fmuellner gnome org>
Date:   Fri Sep 21 22:10:07 2012 +0200

    panelCorner: Only overlap panel if necessary
    
    The panel corners overlap the panel in order to hide the underline
    used for active buttons where it is supposed to arc downwards
    following the roundness of the corner.
    Unfortunately this prevents us from using a transparent panel background,
    as the overlapped area ends up with the wrong transparency. Work around
    this limitation by only overlapping the panel if there is a visible
    border.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=684573

 js/ui/panel.js |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/js/ui/panel.js b/js/ui/panel.js
index ba02a49..65ca664 100644
--- a/js/ui/panel.js
+++ b/js/ui/panel.js
@@ -882,10 +882,13 @@ const PanelCorner = new Lang.Class({
         let backgroundColor = node.get_color('-panel-corner-background-color');
         let borderColor = node.get_color('-panel-corner-border-color');
 
+        let noOverlap = borderColor.alpha == 0;
+        let offsetY = noOverlap ? borderWidth : 0;
+
         let cr = this.actor.get_context();
         cr.setOperator(Cairo.Operator.SOURCE);
 
-        cr.moveTo(0, 0);
+        cr.moveTo(0, offsetY);
         if (this._side == St.Side.LEFT)
             cr.arc(cornerRadius,
                    borderWidth + cornerRadius,
@@ -894,7 +897,7 @@ const PanelCorner = new Lang.Class({
             cr.arc(0,
                    borderWidth + cornerRadius,
                    cornerRadius, 3 * Math.PI / 2, 2 * Math.PI);
-        cr.lineTo(cornerRadius, 0);
+        cr.lineTo(cornerRadius, offsetY);
         cr.closePath();
 
         let savedPath = cr.copyPath();
@@ -904,6 +907,9 @@ const PanelCorner = new Lang.Class({
         Clutter.cairo_set_source_color(cr, over);
         cr.fill();
 
+        if (noOverlap)
+            return;
+
         let offset = borderWidth;
         Clutter.cairo_set_source_color(cr, backgroundColor);