Capture infrastructure: Part II

[kvark]

Fixes #2238

The PR implements support for capturing all the built-frame stage environment:

• built frames for each document
• cached fonts, glyphs, images, and render targets
• gpu cache

How to use:

• run any example with "--features capture"
• hit "c" to capture, the data is written into "captures/example"
• run wrench with "load" command

TODO:

• cleanup
• rebase
• reviews
• proper external textures support (frame_output example)

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This change is 

[glennw]

Reviewed 31 of 35 files at r1.
Review status: 31 of 35 files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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webrender/src/glyph_cache.rs, line 13 at r1 (raw file):

#[cfg_attr(feature = "capture", derive(Deserialize, Serialize))]
pub struct GenericCachedGlyphInfo<D> {

Maybe it will become clearer later in the review - but why does this need to be made generic?

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Comments from Reviewable

[glennw]

Partial review only so far - will be working through the other files today.

[kvark]

Review status: 31 of 35 files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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webrender/src/glyph_cache.rs, line 13 at r1 (raw file):

Previously, glennw (Glenn Watson) wrote…

Maybe it will become clearer later in the review - but why does this need to be made generic?

The general approach is to have all the Arc<Vec<u8>> things replaced by String storing the relative path to a binary file (e.g. images/10.raw). In order to avoid code duplication, I made this struct generic over the data.

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Comments from Reviewable

[glennw]

Reviewed 4 of 35 files at r1, 1 of 1 files at r2.
Review status: all files reviewed at latest revision, 2 unresolved discussions.

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webrender/src/device.rs, line 132 at r2 (raw file):

#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ReadPixelsFormat {

I wonder if we should remove this and just use ImageFormat?

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Comments from Reviewable

[glennw]

Looks good to me!

[kvark]

Review status: all files reviewed at latest revision, 2 unresolved discussions, some commit checks failed.

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webrender/src/device.rs, line 132 at r2 (raw file):

Previously, glennw (Glenn Watson) wrote…

I wonder if we should remove this and just use ImageFormat?

I wish we could. Problem is - the ImageFormat doesn't have RGBA versus BGRA...

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Comments from Reviewable

[kvark]

@glennw please take a look at the last commit dealing with external images. There is nothing particularly concerning there, but it's new code. frame_output example capturing works now 🎉 , and this should be ready to land.

[glennw]

The last commit looks good to me. You could perhaps expand on the TODO? comments with some more details, but otherwise looks fine.

[kvark]

Thanks @glennw ! This is done now.
@bors-servo r=glennw

[bors-servo]

📌 Commit aeb2c60 has been approved by glennw

[bors-servo]

⌛ Testing commit aeb2c60 with merge 1eb0032...

[kvark]

@bors-servo r-
Didn't realize read_pixels_into is used by Gecko. Need to re-expose it.

[kvark]

Should be good now. read_pixels_into is back to original form.
@bors-servo r=glennw

[bors-servo]

📌 Commit 712e62f has been approved by glennw

[bors-servo]

⌛ Testing commit 712e62f with merge 39abbda...

[bors-servo]

☀️ Test successful - status-appveyor, status-taskcluster
Approved by: glennw
Pushing 39abbda to master...