The track's "ShaderEffect / ColorOverlay / MultiEffect render NOTHING on the
software path this port runs on" doctrine was measured FALSE on 2026-07-29:
qbz-qt runs on the GPU (OpenGL RHI, threaded render loop, vsync 5.56ms). The
claim came from an offscreen session, and QT_QPA_PLATFORM=offscreen forces
software by definition. Every design it justified needed re-deciding.
- RoundedImage was a Canvas (renderTarget: Canvas.Image) that rasterised with
QPainter on the CPU AND uploaded a texture per repaint, for every cover in
the app, purely to round a corner identical in every frame of that image's
life. It is now layer.enabled + MultiEffect { maskSource } — an FBO rendered
once and cached for static content. Rectangle { radius; clip: true } cannot
do this: clip in Qt Quick is a RECTANGULAR scissor and ignores radius.
maskThresholdMin/maskSpreadAtMin are 0.5/1.0, NOT the 0.0/0.0 that looks
natural: 0.0 collapses Qt's mask smoothstep to step(0, alpha) and every
pixel with any alpha snaps fully opaque — measured 0 antialiased pixels at
radius 40 against the Canvas's 292. At 0.5/1.0 it is 308, ramp [0,51,219,255].
A software machine keeps the Canvas arm (GraphicsInfo.api), and
QBZ_QT_ROUND_MODE=canvas pins it on a GPU machine where the mask misbehaves.
- VizSettle drove the spectrum from FrameAnimation, i.e. every rendered frame:
180fps on this box for data the producer publishes at TARGET_FPS = 30. Now a
16ms Timer; the wall-clock maths is unchanged.
- SpectrumBand's per-bar y was a SECOND JS binding derived from height. An
anchor does the same arithmetic in C++ with no binding at all, and each FFT
frame is materialised into a plain array once per publish instead of being
read element by element across the JS/C++ boundary. Bindings per tick: bars
28 (was 56), waveform 48 (was 96), energy 5 (was 10).
QQuickPaintedItem was investigated and rejected with evidence: cxx-qt 0.7.3
emits X(QObject* parent) : base(parent), which does not compile against
QQuickPaintedItem(QQuickItem*), paint() is pure virtual, and there is zero
precedent for a custom base class in this workspace. Qt 6 ShaderEffect takes
no GLSL, only precompiled .qsb, which would make the build depend on a Qt
tool whose path differs on macOS.
- PlaylistCollage point-sampled its mosaic in its own Canvas
(Context2D.drawImage does not filter when it scales — measured RMSE 0.000
against nearest-neighbour). It now draws through RoundedImage.
- The scaled-derivative cache had no eviction at all and the .jpg -> .png key
change had orphaned 1251 files. Boot housekeeping sweeps the orphans once and
bounds the directory at 64 MB, LRU by mtime. Verified by effect: first run
deleted 1259 files / 10.05 MB, every run since reports 0, and the directory
is 14 MB. The eviction is only survivable because RoundedImage clears
_scaled on Image.Error and re-requests.
- For You artwork patched the rails in place instead of republishing the
document, which was resetting contentY. HomeView is destroyed on every
navigation, so the patch map is re-handed on mount through
QbzHome.refreshForyouArt() — otherwise the Radio rail and the Spotlight hero
went blank for the rest of the session after one navigation, and the skeleton
pulse Timer stayed pinned ON, defeating the fix it belonged to.
- Spotlight's placeholder gated on the local path instead of the remote url, so
it flashed a glyph on a cold cache where the Slint does not.
The retired doctrine is corrected wherever it was load-bearing for a decision.
The pre-baked icon tints are deliberately NOT reopened and no drop-shadows are
added: both are visual changes, not perf fixes.
cc
vicrodh
d4667f5ea9