fix(refr): fixes for triple buffering (v2) by kpajko79 · Pull Request #10445 · lvgl/lvgl

kpajko79 · 2026-08-08T07:12:52Z

This is a refactor of #10409 . See that for the description of the triple buffering-related fix.

After realizing the purpose of sync_cb() instead of hijacking I have renamed and documented it to prevent accidental use.

github-actions · 2026-08-08T07:21:59Z

Hi 👋, thank you for your PR!

We've run benchmarks in an emulated environment. Here are the results:

ARM Emulated 32b - lv_conf_perf32b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	101	38	24	24	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)
Empty screen	101	44	7	7
Moving wallpaper	101	14	70	70
Single rectangle	101	49	0	0
Multiple rectangles	101	49	3 (-1)	3 (-1)
Multiple RGB images	101	47	16	16
Multiple ARGB images	101	48 (-1)	13	13
Rotated ARGB images	101	25	38	38
Multiple labels	101	60	13	13
Screen sized text	101	24	39	39
Multiple arcs	101	42	20	20
Containers	101	49	5	5
Containers with overlay	101	14	68	68
Containers with opa	101	48	13	13
Containers with opa_layer	101	43 (-2)	19 (+1)	19 (+1)
Containers with scrolling	101	31	30	30
Widgets demo	101	30	30	30
All scenes avg.	101	38	24	24

ARM Emulated 64b - lv_conf_perf64b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	101	40	21	21	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)
Empty screen	101	44	7	7
Moving wallpaper	101	17	56	56
Single rectangle	101	49	0	0
Multiple rectangles	101	49	3	3
Multiple RGB images	101	49	13 (-1)	13 (-1)
Multiple ARGB images	101	49	13 (+1)	13 (+1)
Rotated ARGB images	101	44 (+1)	20	20
Multiple labels	101	51	13	13
Screen sized text	101	24	39	39
Multiple arcs	101	44	19	19
Containers	101	49	4	4
Containers with overlay	101	14	66	66
Containers with opa	101	50	12 (+1)	12 (+1)
Containers with opa_layer	101	45 (-1)	17	17
Containers with scrolling	101	33	29	29
Widgets demo	101	31	29	29
All scenes avg.	101	40	21	21

Disclaimer: These benchmarks were run in an emulated environment using QEMU with instruction counting mode.
The timing values represent relative performance metrics within this specific virtualized setup and should
not be interpreted as absolute real-world performance measurements. Values are deterministic and useful for
comparing different LVGL features and configurations, but may not correlate directly with performance on
physical hardware. The measurements are intended for comparative analysis only.

🤖 This comment was automatically generated by a bot.

kpajko79 · 2026-08-08T07:26:24Z

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kpajko79 · 2026-08-08T10:37:06Z

I have ran the tests locally under WSL2. The same two tests fail as on master. Something broke I1, I2 and I4 rendering before in test_image_clip_radius and bin_image_stride1_UNCOMPRESSED_simple in test_image_formats.
The differences between the rendered and reference images: https://postimg.cc/gallery/rzTqvhv

kpajko79 · 2026-08-09T14:19:15Z

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All reported issues were addressed across 17 files

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kpajko79 · 2026-08-09T15:02:48Z

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kpajko79 · 2026-08-09T15:13:22Z

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AndreCostaaa · 2026-08-18T07:04:12Z

Hi let's get #10448 merged first so that we can ensure this doesn't introduce any regressions

kpajko79 · 2026-08-18T07:45:52Z

Hi @AndreCostaaa,

Fine, but I think this pull request should wait for #9139 to be merged too, if it is accepted.

AndreCostaaa · 2026-09-01T05:07:09Z

#10448 is merged, feel free to rebase

kpajko79 · 2026-09-01T17:52:03Z

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… use case and document it

…he translation and the call to partial_sync_cb()

kpajko79 · 2026-09-01T18:14:25Z

Hi @AndreCostaaa,

I have completed the rebase and there is one thing left. Somebody created a unit test for the previous undocumented state and it is completely wrong! sync_cb has nothing to do with DIRECT mode rendering, it is strictly for PARTIAL. Sorry but I'm not going to fix that.

Another garbage from the code:

" /*Two more frames, each of them refreshing an unrelated area. The rectangle
has to be propagated to all of the three buffers./
"

No this is not true at all!

kpajko79 · 2026-09-01T18:40:50Z

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cubic-dev-ai Bot reviewed Aug 8, 2026

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Comment thread src/core/lv_refr.c

Comment thread include/lvgl/display/lv_display.h Outdated

Comment thread src/display/lv_display_private.h Outdated

kpajko79 mentioned this pull request Aug 8, 2026

fix(refr): Fixes for triple buffering #10409

Closed

kpajko79 marked this pull request as ready for review August 8, 2026 08:09

kpajko79 requested review from AndreCostaaa, axos88 and kisvegabor as code owners August 8, 2026 08:09

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Comment thread include/lvgl/display/lv_display.h Outdated

kpajko79 marked this pull request as draft August 9, 2026 04:45

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Comment thread docs/src/main-modules/display/rotation.mdx

Comment thread src/core/lv_refr.c

Comment thread docs/src/main-modules/display/rotation.mdx Outdated

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Comment thread src/core/lv_refr.c

kpajko79 marked this pull request as ready for review August 9, 2026 16:12

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AndreCostaaa added cmsis RTOS port config labels Aug 31, 2026

AndreCostaaa added core display event misc public-api refresh Core module scripts labels Aug 31, 2026

kpajko79 marked this pull request as draft September 1, 2026 17:25

kpajko79 force-pushed the feature/fix-triple-buffering-v2 branch from d20e2d9 to acd8d9d Compare September 1, 2026 17:50

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kpajko79 added 5 commits September 1, 2026 20:05

feat(display): rename sync_cb() to partial_sync_cb() to emphasize its…

ed8e011

… use case and document it

fix(refr): clean up the triple-buffering support

ce73bde

feat(refr): recover some time by waiting for the flush a bit later

81ad736

fix(refr): rotate the areas into physical frame buffer space before t…

2a7c6f9

…he translation and the call to partial_sync_cb()

feat(display): complete the documentation of partial_sync_cb()

3de28d1

kpajko79 force-pushed the feature/fix-triple-buffering-v2 branch from acd8d9d to 3de28d1 Compare September 1, 2026 18:10

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kpajko79 marked this pull request as ready for review September 1, 2026 18:54

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ARM Emulated 32b - lv_conf_perf32b

ARM Emulated 64b - lv_conf_perf64b

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