Enabling more efficient transparent windowless painting

Brett Wilson brettw at google.com
Thu Apr 8 17:21:28 PDT 2010

On Thu, Apr 8, 2010 at 4:50 PM, Robert O'Callahan <robert at ocallahan.org> wrote:
> That basically sounds good to me. We only need this on X and Windows where
> X/GDI can't be trusted to set alpha values correctly.
> Why do you require the browser to clear the surface? Wouldn't it be more
> efficient for the plugin to clear it?

In Chrome this surface is in shared memory, so it doesn't matter who
clears it from a perf perspective. I just thought it was nice to
define what the state of the buffer is before handing it to the

> We'll also want a similar "draw to GL"/"draw to D3D" API shortly. I'm not
> sure if it's worth lumping that in here or not.

GL sounds like it's more of a replacement of the current painting
model, whereas my proposal is more of a mode on the current one. Does
this sound right to you?

Conceivably, the bitmap produced by my proposal could be converted to
a texture for accelerated painting, although the plugin itself could
not be accelerated.


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