[Webkit-unassigned] [Bug 73186] [Chromium]Draw small cached canvases to an onscreen large canvas is slow when 2D canvas is HW accelerated.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=73186





--- Comment #5 from Jin Yang <jin.a.yang at intel.com>  2011-12-09 07:32:29 PST ---
Thanks for your remainder, I just tested the non-static case you mentioned: I randomly draw rect with different color(fillRect) into the cached canvas, the texture was not re-uploaded.
After debug, I found the root cause is as follow:
1. in fillRect to the cached canvas, it use canvas->fDevice->bitmap to finish the operation. As pixels changed, the bitmap's generation id will set to 0;
2. when draw this cached canvas to accelerated big canvas, it will use m_data.m_image->bitmap(as my fix) to finish the operation. the bitmap's generation id is not 0, so we will use this id to find the cached texture, the texture is not re-loaded.

I tried the below code, that is to check bitmap's content is changed before we draw. It works and the texture will be re-uploaded after the source canvas content changed:
    // if the bitmap's content has changed, we have to update m_image.
    if( m_data.m_platformContext.bitmap()->getGenerationID() != m_data.m_image.get()->nativeImageForCurrentFrame()->bitmap().getGenerationID()) {
        m_data.m_image = BitmapImageSingleFrameSkia::create(*m_data.m_platformContext.bitmap(), false);
    }

    if (drawNeedsCopy(m_context.get(), context)) {
        // We are drawing to our own buffer, copy the source buffer first
        RefPtr<Image> copy = copyImage(CopyBackingStore);
        context->drawImage(copy.get(), styleColorSpace, destRect, srcRect, op, useLowQualityScale);
    } else
        context->drawImage(m_data.m_image.get(), styleColorSpace, destRect, srcRect, op, useLowQualityScale);

Any suggestion to it? Thanks

(In reply to comment #4)
> (From update of attachment 116699 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=116699&action=review
> 
> > Source/WebCore/platform/graphics/skia/ImageBufferSkia.cpp:122
> > +    m_data.m_image = BitmapImageSingleFrameSkia::create(*m_data.m_platformContext.bitmap(), false);
> 
> Thank you for the patch.
> 
> I'm wondering how this change will behave in the non-static case:  if you subsequently change the source canvas and re-draw it to the destination, since this bitmap has already been copied will it be successfully generation-bumped and the texture re-uploaded?  Have you tested this case?
> 
> > Source/WebCore/platform/graphics/skia/ImageBufferSkia.cpp:164
> > +    if (context == m_context) {
> 
> I've been changing this code a bit recently.  You'll have to sync up to tip-of-tree, since this condition has changed.

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