Progressive blur under fixed chrome (real variable blur like Craft) #32

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opened 2026-09-15 17:37:16 +00:00 by kayg · 1 comment

kayg commented

2026-09-15 17:37:16 +00:00

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Request (user, 2026-09-15)

The progressive-blur edge ('glur') was never verified in the app; Craft ships a real progressive (variable) blur under its fixed chrome although the API is private. Calternal is self-distributed (AGPL), so using CoreAnimation's private variable blur is acceptable.

Decision

Implement one shared ProgressiveBlurEdgeView (AppKit, NSView-backed): a CALayer with CAFilter type variableBlur created through KVC (filterWithType:), inputRadius ~ 18, inputMaskImage = a vertical gradient CGImage (opaque at the chrome edge → clear over the reach; asymmetric per the progressive-blur-edge skill), inputNormalizeEdges true; runtime-checked — if the filter class/type is unavailable, fall back to the existing alpha-mask dissolve. Apply it under every fixed chrome where content scrolls beneath: sidebar header (Timeline/Analytics) top edge and the sidebar bottom/footer, the search capsule's result list edges, the editor's floating toolbar row. One implementation, every front.

Acceptance

VM screenshots light AND dark, over bright busy content (the A0 note with the colour-bar images, and the timeline), sidebar scrolled so rows pass under the header: rows visibly blur progressively before the header, no hard line, no banding; side-by-side with Craft's header blur on the VM.
Scroll-spam gate: key-repeat scroll under the blurred edge stays at frame rate (Release sample: no per-frame mask regeneration; the mask image is built once per size).
cua script Scripts/vm/progressive_blur_check.py: scroll, capture the header band, assert a monotonic blur/contrast gradient across the band (row edge sharpness decreasing toward the chrome) rather than a step.

## Request (user, 2026-09-15) The progressive-blur edge ('glur') was never verified in the app; Craft ships a real progressive (variable) blur under its fixed chrome although the API is private. Calternal is self-distributed (AGPL), so using CoreAnimation's private variable blur is acceptable. ## Decision Implement one shared `ProgressiveBlurEdgeView` (AppKit, NSView-backed): a `CALayer` with `CAFilter` type `variableBlur` created through KVC (`filterWithType:`), `inputRadius` ~ 18, `inputMaskImage` = a vertical gradient CGImage (opaque at the chrome edge → clear over the reach; asymmetric per the progressive-blur-edge skill), `inputNormalizeEdges` true; runtime-checked — if the filter class/type is unavailable, fall back to the existing alpha-mask dissolve. Apply it under every fixed chrome where content scrolls beneath: sidebar header (Timeline/Analytics) top edge and the sidebar bottom/footer, the search capsule's result list edges, the editor's floating toolbar row. One implementation, every front. ## Acceptance - VM screenshots light AND dark, over bright busy content (the A0 note with the colour-bar images, and the timeline), sidebar scrolled so rows pass under the header: rows visibly blur progressively before the header, no hard line, no banding; side-by-side with Craft's header blur on the VM. - Scroll-spam gate: key-repeat scroll under the blurred edge stays at frame rate (Release sample: no per-frame mask regeneration; the mask image is built once per size). - cua script `Scripts/vm/progressive_blur_check.py`: scroll, capture the header band, assert a monotonic blur/contrast gradient across the band (row edge sharpness decreasing toward the chrome) rather than a step.

kayg commented

2026-09-16 01:20:58 +00:00

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Overnight (Main): wave19/progressive-blur @ 4553333a merged into desktop-test (255df592). Shipping path is mailternal's mailWindowDissolve alpha mask (shared interface); the CABackdropLayer variableBlur attempt is behind CALTERNAL_BACKDROP_BLUR=1 because the probe never proved the mask is honoured (blurs uniformly + shows a material plate). VM dark evidence on the merged build: rows fade under the header and under the bottom Space bar, no black band (/tmp/vm/dt6-mid.png, /tmp/progressive-blur-evidence/sidebar-fallback-dark.png). Real progressive blur remains open.

Overnight (Main): `wave19/progressive-blur` @ 4553333a merged into desktop-test (255df592). Shipping path is mailternal's `mailWindowDissolve` alpha mask (shared interface); the CABackdropLayer `variableBlur` attempt is behind `CALTERNAL_BACKDROP_BLUR=1` because the probe never proved the mask is honoured (blurs uniformly + shows a material plate). VM dark evidence on the merged build: rows fade under the header and under the bottom Space bar, no black band (/tmp/vm/dt6-mid.png, /tmp/progressive-blur-evidence/sidebar-fallback-dark.png). Real progressive blur remains open.

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kayg/calternal-macos#32

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