Performance: Do Graphics the Right Way
summary
Practical recipe for fast Qt graphics: prefer opengl for main view and raster for UI — raster makes state changes and small draws cheap while OpenGL handles huge pixel throughput but has a 120 μs setup cost per glDrawArrays call. Two rules: minimize state/clip changes and combine many primitives into one call (drawPixmapFragments hits this). Static text (QStaticText) cuts layout cost — demo goes from ~80 ms per frame (widget per-button) to ~16 ms (cached pixmaps, 60 fps). Offload image decode/compose to a worker thread to keep UI at ~58–59 fps.
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chapters (6)
- 0:00Introduction and background
- 4:17Graphics systems concept
- 19:53Painting rules and optimizations
- 33:50Text rendering challenges
- 46:51Threading for responsive UI
- 57:20Demo and summary
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