Bug 36947 – Transparent Background of Silverlight Apps lead to black backgrounds and repainting errors

• Component: Plug-ins
• Status: RESOLVED INVALID

[Henrik]

Created attachment 52280 [details]
Sample-screenshot and Silverlight Demo App

Szenario:
Having a Silverlight Application with WindowlessMode = true and a transparent Background, the App will strech all over the screen(this detail is not important for this bug). 
The effect should be, that html liying under Silverlight will be shown through the transparent parts of Silverlight.

When executing such configuration in Gecko-Based Browsers or the IE, everything works fine. With Webkit, Background remains black (not the Background of the SL-App, nor the Background of the html) - just a black color from the rendering pipeline and when dragging a Silverlight element around the screen, no redrawing is done, the older positions if this element will be shown to. - Until a general redrawing is triggered, like a window resize.

In the appending Archive, you can find a screenshot visualizing this effect and a small Silverlight Demo for confirming.
What this app does:
- A blue background-image defined in html
- A nearly complete transparent silverlight Application, stretching all over the html
- A draggable circle, initialized in the middle

Hint:
In the newest Chrome Source(not the currently release) was a Bugfix for this issue. Maybe this can help you finding the corresponding sources.

[Alexey Proskuryakov]

Confirmed with 56924. Only happens in 64 bit.

[Alexey Proskuryakov]

As far as Safari is concerned, this code is not in open source. Closing as INVALID as a non-WebKit issue per our policy.

But we've now fixed this in close source part of WebKit, it should work in the next nightly build.