What are the thick orange borders when "Show layer borders" is enabled in DevTools?

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Xianzhu Wang

Aug 16, 2022, 5:28:30 PM8/16/22
to graphics-dev
Hi, graphics-dev,

When I enable "Show layer borders" in the Rendering panel in DevTools, there are thick orange borders shown in the page, see this video. I see them on Windows, Mac and ChromeOS, but not Linux through remote desktop. I don't think they are layer borders or tile borders. Is there a document about them?


Sunny Sachanandani

Aug 16, 2022, 5:36:41 PM8/16/22
to Xianzhu Wang, graphics-dev
Maybe you can try matching the color with the predefined ones in debug_colors.cc. There are several orange like colors there though :/

Xianzhu Wang

Aug 16, 2022, 6:19:18 PM8/16/22
to Sunny Sachanandani, graphics-dev
There are 4 orange like colors:
1 TiledContentLayerBorderColor
2 SurfaceDamageRectBorderColor
3 NonFastScrollableRectBorderColor
4 MainThreadScrollingReasonRectBorderColor

The thick orange borders I see are not 1, 3 or 4. Suspected 2, but the thick orange borders are obviously different from what I see with --show-surface-damage-rects on Linux. There are also no debug borders with such a thick width (>=5 pixels).

I want to understand them because they look very annoying when I just want to see layer borders.

Xianzhu Wang

Aug 17, 2022, 11:43:21 PM8/17/22
to Sunny Sachanandani, graphics-dev
I bisected on Mac to https://chromium.googlesource.com/chromium/src/+log/7b74f72619ebc25c86e3cc09a407d1e43ca80ee7..612daee53a0c8a3aa91881e5eb799e752f0586c0 which includes the CL to enable SkiaRenderer on Mac.

I debugged a bit and found that the color used is TiledContentLayerBorderColor to show layer borders for tiled layers, but the borders shown are obviously incorrect. Filed crbug.com/1354009.
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