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fix(v2): propagate Retina backing scale factor to WKWebView#5212

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fix/5111-wkwebview-devicepixelratio
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fix(v2): propagate Retina backing scale factor to WKWebView#5212
leaanthony wants to merge 1 commit into
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fix/5111-wkwebview-devicepixelratio

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@leaanthony

@leaanthony leaanthony commented Apr 22, 2026

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Summary

Fixes #5111

WKWebView does not automatically propagate the display's backing scale factor to JavaScript's devicePixelRatio when content is loaded via the custom wails:// URL scheme. This causes devicePixelRatio to return 1 on Retina displays, resulting in blurry canvas rendering for any app using <canvas> — terminal emulators, chart libraries, drawing tools, games, and code editors.

Changes

  • Added _setOverrideDeviceScaleFactor: SPI call in WailsContext.m after WKWebView initialization
  • Added SPI category declaration in WailsWebView.h
  • Added test in v2/test/5111/

The SPI is stable since macOS 10.11 and is used by Electron, Playwright, and WebKit's own test infrastructure.

Test plan

  • Build a Wails v2 app on macOS with a Retina display
  • Check window.devicePixelRatio returns 2 (not 1)
  • Verify canvas rendering is sharp at native resolution
  • Test on non-Retina display that devicePixelRatio returns 1

fix(v2): propagate Retina backing scale factor to WKWebView
38d96e3 
WKWebView does not automatically propagate the display's backing scale
factor to JavaScript's devicePixelRatio when content is loaded via a
custom URL scheme (wails://). This causes devicePixelRatio to return 1
on Retina displays, resulting in blurry canvas rendering.

Fix by calling _setOverrideDeviceScaleFactor: on the WKWebView after
initialization with the screen's backingScaleFactor. This SPI is stable
since macOS 10.11 and is used by Electron, Playwright, and WebKit's
own test infrastructure.

Fixes #5111
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@leaanthony

leaanthony commented May 2, 2026

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🤖 PR Triage Review

✅ Accepted

Propagates Retina backing scale factor to WKWebView (v2 macOS). Fixes high-DPI rendering.

Platform: macOS (v2)

Next Steps: Dispatching for Mac testing.

Reviewed by Wails PR Reviewer Bot

@leaanthony leaanthony added this to the v2.13.0 milestone May 20, 2026
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WKWebView reports devicePixelRatio=1 on macOS Retina displays (custom URL scheme)

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