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Add a debugging feature to visualize overdraw. #2963

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merged 2 commits into from Aug 11, 2018
Merged

Add a debugging feature to visualize overdraw. #2963

merged 2 commits into from Aug 11, 2018
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pcwalton commented Aug 10, 2018 •
edited by larsbergstrom

Lighter shades of orange indicate more overdraw.

This has already helped to diagnose a few issues (e.g. #2958).

r? @gw3583

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@pcwalton pcwalton requested a review from gw3583 Aug 10, 2018
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gw3583 commented Aug 10, 2018

Looks like there are some shader validation failures on CI:

https://ci.appveyor.com/project/servo/webrender/build/1.0.10141#L304

It might just be related to needing to pass the right defines to the validation code, if they've changed.
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Reviewed 19 of 19 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @pcwalton)

webrender/res/brush_debug_overdraw.glsl, line 1 at r1 (raw file):

/* This Source Code Form is subject to the terms of the Mozilla Public

Instead of having a separate shader, we could perhaps have just had an #ifdef in the fragment shader skeleton for brush.glsl? Doesn't really matter either way though.
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gw3583 commented Aug 10, 2018

We'll need to resolve the shader validation errors on CI above. If we instead added an #ifdef in brush.glsl we could probably select the debug variant of each normal brush shader. This might simplify some of the complexity involved with the vecs_per_brush code?

We should do a try run too, to make sure that nothing breaks with any of the weird shader combinations. I can do that on Monday if you're not sure how to do a gecko try.
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gw3583 commented Aug 10, 2018

(if you think it's simpler to leave as is, that's fine too - the above is just what came to mind when looking through the code).
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Left comments in reviewable.
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gw3583 commented Aug 10, 2018

This is a really helpful feature to have, btw! 👍
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kvark commented Aug 10, 2018

A screnshot would be handy here
@pcwalton pcwalton force-pushed the pcwalton:show-overdraw branch from 65a47f4 to 50a1293 Aug 10, 2018
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pcwalton commented Aug 10, 2018

@gw3583 Updated patch per your suggestion. This is way simpler :)

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Here's a before and after:

screen shot 2018-08-10 at 12 01 47 pm

screen shot 2018-08-10 at 12 01 51 pm
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kvark reviewed Aug 10, 2018
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webrender/src/renderer.rs Outdated
// Sets the blend mode. Blend is unconditionally set if the "show overdraw" debugging mode is
// enabled.
fn set_blend(&self, mut blend: bool) {
if !self.debug_flags.contains(DebugFlags::SHOW_OVERDRAW) {

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shouldn't this be the other way around? if self.debug_flags.contains(DebugFlags::SHOW_OVERDRAW) { blend = true; }

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pcwalton Aug 10, 2018

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Doh!
webrender/src/renderer.rs
@@ -4013,6 +4020,47 @@ impl Renderer {
}
self.device.end_frame();
}

// Sets the blend mode. Blend is unconditionally set if the "show overdraw" debugging mode is

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shouldn't it only affect the final (screen) pass?

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Could you elaborate?

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We render a frame in multiple passes. All but the last one go into off-screen targets. Since we are only displaying the screen overdraw, we don't want the blending overrides to affect rendering in any other passes than the last one.

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OK, changed it.
webrender/src/shade.rs Outdated
brush_radial_gradient: BrushShader,
brush_linear_gradient: BrushShader,
brush: BrushShaders,
brush_debug_overdraw: BrushShaders,

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a brush shader struct contains 3 versions:

struct BrushShader {
    opaque: LazilyCompiledShader,
    alpha: LazilyCompiledShader,
    dual_source: Option<LazilyCompiledShader>,
}

Would it make sense to add a 4th for the debug overdraw instead of duplicating the whole thing?
webrender/res/brush_debug_overdraw.glsl Outdated
@@ -0,0 +1,29 @@
/* This Source Code Form is subject to the terms of the Mozilla Public

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is this shader still used?
@pcwalton pcwalton force-pushed the pcwalton:show-overdraw branch from 50a1293 to 6037640 Aug 10, 2018
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pcwalton commented Aug 10, 2018

Comments addressed.
@pcwalton pcwalton force-pushed the pcwalton:show-overdraw branch from 6037640 to a03ab4b Aug 10, 2018
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pcwalton commented Aug 10, 2018

Comment addressed.
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Thank you! I got one last nit, otherwise shipit.
webrender/src/renderer.rs Outdated
@@ -2304,7 +2308,7 @@ impl Renderer {

self.device.disable_scissor();
self.device.disable_depth();
self.device.set_blend(false);
self.set_blend(false, true);

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uh, that's a bit confusing when reading the code.
can have an enum TargetKind or something like this?
pcwalton added 2 commits Aug 10, 2018
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Add a debugging feature to visualize overdraw.
2e96378 
Lighter shades of orange indicate more overdraw.

This has already helped to diagnose a few issues (e.g. #2958).
@pcwalton
Add a "total pixels drawn" line to the debug overlay, and express sam…
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a80d7e1 
…ple counts

as percentages to make them clearer
@pcwalton pcwalton force-pushed the pcwalton:show-overdraw branch from a03ab4b to a80d7e1 Aug 11, 2018
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pcwalton commented Aug 11, 2018

Comment addressed. r? @kvark
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kvark commented Aug 11, 2018

Wonderful, thank you!
@bors-servo r+
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bors-servo commented Aug 11, 2018

📌 Commit a80d7e1 has been approved by kvark
bors-servo added a commit that referenced this pull request Aug 11, 2018
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Auto merge of #2963 - pcwalton:show-overdraw, r=kvark
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002c7f6 
Add a debugging feature to visualize overdraw.

Lighter shades of orange indicate more overdraw.

This has already helped to diagnose a few issues (e.g. #2958).

r? @gw3583

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This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/webrender/2963)
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bors-servo commented Aug 11, 2018

⌛ Testing commit a80d7e1 with merge 002c7f6...
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bors-servo commented Aug 11, 2018

☀️ Test successful - status-appveyor, status-taskcluster
Approved by: kvark
Pushing 002c7f6 to master...
@bors-servo bors-servo merged commit a80d7e1 into servo:master Aug 11, 2018
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code-review/reviewable 4 files, 6 discussions left (gw3583, kvark, pcwalton)
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