1627413 - Software WebRender lacks support for supplying LOD bias when sampling 2DArrays (reftests/filters/svg-filter-composite.yaml)

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P3)

Description

[Jim Blandy :jimb]

The code generated for the call to texture in sampleInUvRect passes 0 for the level-of-detail bias argument. This means it calls glsl::texture(sampler2DArray, vec3, Float) , which is stubbed out.

Since the bias to the LOD calculation is zero, it's unclear to me why sampleInUvRect needs to pass that argument at all.

Comment 1

[Jim Blandy :jimb]

Comments in the code suggest that Firefox does not use mipmaps, but Servo does. Servo doesn't use Software WebRender, so I wonder if that definition of texture in SWGL could just call the next overload that takes no bias argument.

Comment 2

[Jim Blandy :jimb]

Same problem: reftests/filters/svg-filter-offset.yaml

Comment 3

[Jim Blandy :jimb]

This seems to be responsible for all current crashes in reftests/filters (12 tests).

Of course, once we fix this that might uncover more crashes, but this is at least entailed in those.

Comment 4

[Connor Brewster [:cbrewster]]

I'm the one who wrote that call to texture, I'm not sure why I passed 0 for LOD bias. I believe it should be okay to just remove it. Also this shader is currently not used by Firefox or Servo at the moment, but hopefully that will change soon once I have finished more work on SVG filter support.

Comment 5

[Jim Blandy :jimb]

Oh, neat. Thanks!

Comment 6

[Jim Blandy :jimb]

Attachment: Bug 1627413: WebRender: Don't pass level-of-detail bias value to GLSL texture function. r?cbrewster

The sampleInUvRect function in gfx/wr/webrender/res/cs_svg_filter.glsl calls
texture, passing the optional third argument that specifies a bias to the
sampler's level-of-detail calculation, used for mipmap interpolation. However,
the texture override in gfx/wr/swgl/src/glsl.h that accepts this parameter
is stubbed out, with an assert(0). This causes twelve tests in
gfx/wr/wrench/reftests/filters to crash.

Nothing in Firefox uses mipmaps, and Servo doesn't use Software WebRender, so it
should be fine for that call to texture to simply not pass the level-of-detail
bias.

This patch makes that change.

Comment 7

[Lee Salzman [:lsalzman]]

Attachment: Bug 1627413 - implement texture lod-bias. r?jimb

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/89e164da5af7
WebRender: Don't pass level-of-detail bias value to GLSL texture function. r=cbrewster

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/80476f6d2daa
implement texture lod-bias. r=jimb

Comment 10

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/89e164da5af7
https://hg.mozilla.org/mozilla-central/rev/80476f6d2daa