Bugfix/70733 add white backing in editor #71570
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dsas
commented
Sep 9, 2025
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| .block-editor-block-preview__content-iframe { | ||
| // Ensure a white backing layer for consistent semi-transparent color blending | ||
| background-color: $white; |
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There's a brief flash of the darker colour while this loads 🤔
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Flaky tests detected in 562efcb. 🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/18498117312
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t-hamano
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Global Styles
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Why doesn’t setting the iframe to white work? |
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I see, I guess because of zoom out. |
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Sorry I’m mobile atm. To what element are global styles backgrounds applied? Is it the body? If so, could we make the html element white? |
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The global styles background is applied to the 
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ellatrix
reviewed
Sep 20, 2025
| position: absolute; | ||
| inset: 0; | ||
| background-color: $white; | ||
| } |
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Why is this added a second time? Maybe it needs a comment?
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Also isn't .editor-visual-editor outside the iframe? Why does it need to use a pseudo element here?
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The white background-color should be applied between the body element (which gets the theme background-color applied) and any Gutenberg chrome. This ensures the behaviour is as close as possible to the front-end site (though technically speaking "white" here is UA dependent).
The GB chrome is implemented in different ways in different modes. Focusing purely on background-color:
- The general editor sets
iframe.edit-site-visual-editor__editor-canvasto be transparent and so the.editor-visual-editorbackground-color shines through. - The template part editor (e.g. header editing) sets some of its styling inside the iframe - it sets a background-color on
iframe.edit-site-visual-editor__editor-canvas html.block-editor-iframe__html - The style editing mode sets the iframe.edit-site-visual-editor__editor-canvas to transparent and so the
.edit-site-layout:not(.is-full-canvas) .editor-visual-editorbackground-color shines through - The zoomed-out mode (e.g. pattern inserter) sets some of its styling inside the iframe too - it sets a background-color on
html.edit-site-visual-editor__editor-canvas iframe.block-editor-iframe__html.is-zoomed-out(as well as setting background-color:initial)
In short, it's repeated because the background in gutenberg is complicated and handled diffusely (though the new --wp-editor-canvas-background variable consolidates it somewhat).
I considered the comment for the background-color above it to cover the explanation as to why it's repeated.
I think you're right about this not needing to be use a pseudo element. The iframe itself could probably just be set below to use $white.
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This variable was not defined inside the iframe, and hence the grey background was not being set in zoomed-out mode.
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What?
Closes #70733
It's worth pointing out that this PR is a step forward to aligning GB with the front-end, but isn't likely to be completely exhaustive in reference to treatment of alpha transparency on site elements.
Adds white "backing layers" to the editor canvas so that semi-transparent site background colours blend accurately and match the frontend.
Why?
The site editor canvas isn't always white - when inserting patterns, normal template editing or using the left hand navigation to change things. This causes transparent RGBA site backgrounds (e.g., #F5F6FE30) to blend against that background instead of the intended white, leading to a visible color mismatch between the editor and the frontend.
This change builds upon an unmerged PR #70737 that @R1shabh-Gupta started and @t-hamano reviewed.
How?
Testing Instructions
Screenshots or screencast
(Using a test background colour of
#503aa830)