Bug 44064 – GraphicsContext3D::reshape is clearing using current clear color instead of transparent

• Status: RESOLVED
• Resolution: FIXED
• Component: WebGL

[Dave Hyatt]

The WebGL spec says when you resize the canvas (what happens in our reshape call), the buffer should be cleared and filled with transparent.  We're incorrectly filling with the current clear color instead.

[Kenneth Russell]

The bug is in GraphicsContext3DMac.mm. It should be querying the clear color, setting it to (0, 0, 0, 0) before the clear call, and resetting it afterward.

[Chris Marrin]

(In reply to comment #1)
> The bug is in GraphicsContext3DMac.mm. It should be querying the clear color, setting it to (0, 0, 0, 0) before the clear call, and resetting it afterward.

Yes, this is why I took the bug. Because it is so simple :-)

[Chris Marrin]

(In reply to comment #2)
> (In reply to comment #1)
> > The bug is in GraphicsContext3DMac.mm. It should be querying the clear color, setting it to (0, 0, 0, 0) before the clear call, and resetting it afterward.
> 
> Yes, this is why I took the bug. Because it is so simple :-)

But on a serious note, the test case should be testing this, but it's not. I will add this test to the testcase as well.

[Zhenyao Mo]

I guess Ken assigned to me because my code caused the bug.  Since you are working on it, I am assigning it back to you.

[Zhenyao Mo]

This bug is blocking texture/renderbuffer initialization patch in WebCore/graphics/gpu/DrawingBuffer.cpp:reset().

[Zhenyao Mo]

Created attachment 74318 [details]
patch

Will modify khornos's side of the test once it's reviewed here.

[Kenneth Russell]

Comment on attachment 74318 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=74318&action=review

Looks good. Apologies but we decided to change the clear depth upon resizing to the default value (1.0) rather than 0.0 on today's WebGL conference call, so would appreciate it if you could fix that up in these changes.

> WebCore/platform/graphics/gpu/DrawingBuffer.cpp:183
> +        m_context->clearDepth(0);

Per discussion on today's WebGL conference call, we should use the default clear depth, which is 1.0. The spec's been updated with this change.

> WebCore/platform/graphics/opengl/GraphicsContext3DOpenGL.cpp:227
> +        ::glClearDepth(0);

Here too.

> WebKit/chromium/src/WebGraphicsContext3DDefaultImpl.cpp:455
> +        glClearDepth(0);

Here too.

[Zhenyao Mo]

Created attachment 74397 [details]
revised patch

depth clear value all set to 1.

[Kenneth Russell]

Comment on attachment 74397 [details]
revised patch

Looks good to me.

[Zhenyao Mo]

Committed r72431: <http://trac.webkit.org/changeset/72431>