Bug 668319 - Allow to set opacity on ::-moz-tree-cell-text.

r=roc

layout/reftests/bugs/668319-1.xul

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<?xml-stylesheet type="text/css" href="data:text/css,
+tree { height: 100px; -moz-appearance: none; border: none; }
+treecol, treecolpicker { visibility: hidden; }
+treechildren::-moz-tree-cell-text { opacity: 0; }
+"?>
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+  <tree>
+    <treecols>
+      <treecol flex="1"/>
+    </treecols>
+    <treechildren>
+      <treeitem>
+        <treerow>
+          <treecell label="test"/>
+        </treerow>
+      </treeitem>
+    </treechildren>
+  </tree>
+</window>

layout/reftests/bugs/reftest.list

@@ -1646,3 +1646,4 @@ fails-if(layersGPUAccelerated&&cocoaWidget) == 654950-1.html 654950-1-ref.html #
 == 658952.html 658952-ref.html
 == 664127-1.xul 664127-1-ref.xul
 == 660682-1.html 660682-1-ref.html
+== 668319-1.xul about:blank

layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp

@@ -3553,6 +3553,9 @@ nsTreeBodyFrame::PaintText(PRInt32              aRowIndex,
   // out and to paint.
   nsStyleContext* textContext = GetPseudoStyleContext(nsCSSAnonBoxes::moztreecelltext);
 
+  // Obtain opacity value for the image.
+  float opacity = textContext->GetStyleDisplay()->mOpacity;
+
   // Obtain the margins for the text and then deflate our rect by that 
   // amount.  The text is assumed to be contained within the deflated rect.
   nsRect textRect(aTextRect);
@@ -3619,8 +3622,19 @@ nsTreeBodyFrame::PaintText(PRInt32              aRowIndex,
   PRUint8 direction = aTextRTL ? NS_STYLE_DIRECTION_RTL :
                                  NS_STYLE_DIRECTION_LTR;
 
+  gfxContext* ctx = aRenderingContext.ThebesContext();
+  if (opacity != 1.0f) {
+    ctx->PushGroup(gfxASurface::CONTENT_COLOR_ALPHA);
+  }
+
   nsLayoutUtils::DrawString(this, &aRenderingContext, text.get(), text.Length(),
                             textRect.TopLeft() + nsPoint(0, baseline), direction);
+
+  if (opacity != 1.0f) {
+    ctx->PopGroupToSource();
+    ctx->Paint(opacity);
+  }
+
 #ifdef MOZ_TIMELINE
   NS_TIMELINE_STOP_TIMER("Render Outline Text");
   NS_TIMELINE_MARK_TIMER("Render Outline Text");