RemoteGraphicsContextGL ReadPixels does not preserve contents for area that is not part of the Framebuffer

[Kimmo Kinnunen]

RemoteGraphicsContext ReadPixels does not preserve contents for area that is not written

When readPixels is used with source rectangle that contains areas that are not part of the Framebuffer, then the memory contents of the buffer should not be changed for that part.

E.g. when doing
data[0] = 77;
 readPixels(-1, -1, 10000000, 10000000, .., data)

then data[0] should be preserved as 77 as -1,-1 is not part of the framebuffer being read.

Problem since the webp->gpup does not don't transfer the buffer, but also does not risk the calculations to only populate part of the result buffer.

webgl/2.0.0/conformance/reading/read-pixels-test.html [ Failure ]
webgl/2.0.0/conformance2/reading/read-pixels-pack-parameters.html [ Failure ]

[Radar WebKit Bug Importer]

<rdar://problem/75025951>

[John Cunningham]

Created attachment 453856 [details]
Patch

[Kimmo Kinnunen]

Comment on attachment 453856 [details]
Patch

Looks good.
Can you remove the entry at the bottom of LayoutTests/platform/ios-wk2/TestExpectations

webkit.org/b/234536 webgl/2.0.0/conformance/reading/read-pixels-test.html

[John Cunningham]

Created attachment 454000 [details]
Patch for Landing

[John Cunningham]

Created attachment 454137 [details]
Patch for Landing

[EWS]

Committed r291032 (248206@main): <https://commits.webkit.org/248206@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 454137 [details].