Waterfox: 56.2.12: HTML5 canvas is somewhat broken

[tmkk]

To Reproduce
Steps to reproduce the behavior:

1. Go to https://comic-walker.com/contents/detail/KDCW_CW01000002020000_68/ (a free web comic)
2. Click 'Begin Reading'
3. Click on the left edge of the screen and flip a page 3 times
4. No image is drawn on the screen, and browser console says: Error: WebGL warning: drawElements: bound vertex attribute buffers do not have sufficient size for given indices from the bound element array

Expected behavior
The image should be drawn properly.

Desktop

• OS: macOS 10.12.6/Windows 10 1803
• Version: Waterfox 56.2.12

Additional context
It works properly on 56.2.11. I'm not confident but the commit b705c80 looks suspect.

[grahamperrin]

No image is drawn on the screen, …

Not reproducible with Waterfox Classic 56.2.12 on FreeBSD-CURRENT.

[strotee]

The bug happens on Windows 10 LTSC (17763.615) using Waterfox 56.2.12.

[tmkk]

Now I've confirmed that b705c80 is the cause. The problem is in WebGLBuffer::BufferData function in WebGLBuffer.cpp, restoring previously existed mContext->InvalidateBufferFetching(); line fixes the problem.

--- dom/canvas/WebGLBuffer.cpp.orig     2019-07-10 06:00:02.000000000 +0900
+++ dom/canvas/WebGLBuffer.cpp  2019-07-20 16:50:04.000000000 +0900
@@ -134,6 +134,7 @@ WebGLBuffer::BufferData(GLenum target, s

   const bool sizeChanges = (size != ByteLength());
   if (sizeChanges) {
+    mContext->InvalidateBufferFetching();
     gl::GLContext::LocalErrorScope errorScope(*gl);
     gl->fBufferData(target, size, uploadData, usage);
     const auto error = errorScope.GetError();

[grahamperrin]

Thanks!

Bug reproducible with 56.2.12 on Lubuntu.

After two flips to the left:

– and after the third:

Meta/tracking: #538

[MrAlex94]

Now I've confirmed that b705c80 is the cause. The problem is in WebGLBuffer::BufferData function in WebGLBuffer.cpp, restoring previously existed mContext->InvalidateBufferFetching(); line fixes the problem.

--- dom/canvas/WebGLBuffer.cpp.orig     2019-07-10 06:00:02.000000000 +0900
+++ dom/canvas/WebGLBuffer.cpp  2019-07-20 16:50:04.000000000 +0900
@@ -134,6 +134,7 @@ WebGLBuffer::BufferData(GLenum target, s

   const bool sizeChanges = (size != ByteLength());
   if (sizeChanges) {
+    mContext->InvalidateBufferFetching();
     gl::GLContext::LocalErrorScope errorScope(*gl);
     gl->fBufferData(target, size, uploadData, usage);
     const auto error = errorScope.GetError();

Thanks for the fix! https://github.com/MrAlex94/Waterfox/commit/285f3f889d8a6f9c217f7178363991b3c9c45db2