fix(mapbox,google-maps): use css-dpr pixel sizing in overlaid mode to prevent basemap misalignment

[chrisgervang]

Summary

• Passes pixelSizeSource: 'css-dpr' to the luma.gl canvas context in overlaid (non-interleaved) mode for both MapboxOverlay and GoogleMapsOverlay
• This makes luma.gl derive pixel sizes using CSS dimensions × DPR instead of the exact devicePixelContentBoxSize, matching how Mapbox GL, MapLibre, and Google Maps compute their canvas drawing buffer dimensions
• Fixes visible drift between the deck.gl overlay canvas and the basemap at fractional browser zoom levels (90%, 110%, 33%, etc.)
• Bumps @luma.gl/* to 9.3.4 which ships the pixelSizeSource prop (visgl/luma.gl#2588)

Remaining luma.gl fix needed

visgl/luma.gl#2675: The css-dpr mode in luma.gl 9.3.4 has two bugs:

1. The ResizeObserver still watches device-pixel-content-box even in css-dpr mode — this causes major canvas misalignment during real browser zoom (Cmd+/-) due to race conditions in the observer callback
2. Uses Math.round instead of Math.floor — causes 1px mismatch at certain DPR values since Mapbox truncates via implicit canvas.width assignment

Both issues are confirmed fixed by patching luma.gl locally. Once luma.gl ships the fix, this PR will fully resolve #10173.

Impact by environment

Environment	Effect
Pure deck.gl (standalone, no basemap)	No change — default pixelSizeSource remains 'exact'
Mapbox/MapLibre overlaid	Fixed — overlay canvas now matches basemap sizing
Mapbox/MapLibre interleaved	No change — deck sets width: null, height: null, map owns canvas
Google Maps non-interleaved (raster & vector positioning)	Fixed — same treatment
Google Maps interleaved (WebGL overlay)	No change — gl prop present, deviceProps not injected
ArcGIS	No change — renders to external FBO

Root cause

At fractional browser zoom, window.devicePixelRatio becomes non-integer. Mapbox/MapLibre compute canvas pixel size as Math.floor(cssWidth * dpr) (via implicit truncation), while luma.gl's ResizeObserver with device-pixel-content-box reports the true physical pixel count. These can differ significantly, causing the two canvases to have different drawing buffer dimensions and visible misalignment.

The larger issue is that device-pixel-content-box observation fires during DPR changes with potentially stale/racey values, causing the deck.gl canvas to resize out of sync with Mapbox's canvas.

Test plan

• Verify no regression at 100% browser zoom with Mapbox overlay
• Verify drawing buffer dimensions match at fractional DPR (confirmed Math.floor matches Mapbox)
• Verify misalignment is fixed at 50%, 25% browser zoom (requires luma.gl#2675 fix)
• Verify Google Maps overlay renders correctly at fractional zoom
• Verify standalone deck.gl (no basemap) continues to use exact pixel sizing
• Verify interleaved mode is unaffected

Closes #10173 (pending luma.gl#2675)

🤖 Generated with Claude Code

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Note

Medium Risk
Changes how overlay canvases compute drawing-buffer size for Mapbox/Google Maps integrations; behavior is scoped to non-shared-GL paths but can affect alignment and rendering at non-100% zoom until the paired luma.gl fixes land.

Overview
Aligns deck.gl overlay canvas sizing with Mapbox/MapLibre and Google Maps at fractional browser zoom by opting into luma.gl’s pixelSizeSource: 'css-dpr' when Deck owns its own WebGL canvas.

MapboxOverlay always merges deviceProps.createCanvasContext.pixelSizeSource: 'css-dpr' into the Deck it creates in overlaid mode, preserving any existing deviceProps / createCanvasContext fields. GoogleMapsOverlay applies the same merge only when no external gl is passed (non-interleaved / separate overlay canvas); interleaved shared-context paths are unchanged.

Monorepo @luma.gl/* dependencies and peers are bumped from 9.3.3 to 9.3.4 (lockfile resolves 9.3.5). Unit tests assert the css-dpr wiring for Mapbox overlaid mode and Google Maps without external gl, and a fractional-zoom-alignment Vite test app was added to manually verify Mapbox overlay vs basemap dimensions at browser zoom.

^{Reviewed by Cursor Bugbot for commit c983cfd. Bugbot is set up for automated code reviews on this repo. Configure here.}

[coveralls]

coverage: 83.112%. remained the same — chr/deckgl-fix-evaluation into master