fix(slider): allow knob update while dragging even if scroll object is active

[dmd79]

Problem

When dragging a horizontal slider, lv_indev_get_scroll_obj() may
return non-NULL causing update_knob_pos() to return early without
sending LV_EVENT_VALUE_CHANGED. This prevents the slider from
updating continuously during drag as documented.

Root cause

In update_knob_pos(), the check:

if(lv_indev_get_scroll_obj(indev) != NULL)
    return;

exits the function even when the slider is already in dragging mode.

Fix

Skip the scroll object check when the slider is already dragging:

if(lv_indev_get_scroll_obj(indev) != NULL && !slider->dragging)
    return;

Tested

Verified on ESP32-S3 with touchscreen display running ESPHome.

[cubic-dev-ai]

No issues found across 1 file

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[github-actions]

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.	29	37	7	7	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
Empty screen	11	33	0	0	0
Moving wallpaper	2	33	1	1	0
Single rectangle	0	50	0	0	0
Multiple rectangles	0	33	0	0	0
Multiple RGB images	0	39	0	0	0
Multiple ARGB images	11	39	3	3	0
Rotated ARGB images	55 (+1)	44	15	15	0
Multiple labels	7	35	0	0	0
Screen sized text	97	47	20	20	0
Multiple arcs	33	33	7	7	0
Containers	4 (+4)	37	0	0	0
Containers with overlay	98	21	44	44	0
Containers with opa	18	38	1	1	0
Containers with opa_layer	18 (-1)	33 (-1)	6	6	0
Containers with scrolling	44	45	12	12	0
Widgets demo	71 (-1)	40 (+1)	17 (+1)	17 (+1)	0
All scenes avg.	29	37	7	7	0

ARM Emulated 64b - lv_conf_perf64b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	24	37	6	6	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
Empty screen	11	33	0	0	0
Moving wallpaper	1	33	0	0	0
Single rectangle	0	50	0	0	0
Multiple rectangles	0	35	0	0	0
Multiple RGB images	0	39	0	0	0
Multiple ARGB images	11	42	0	0	0
Rotated ARGB images	29	33	9	9	0
Multiple labels	2	35	0	0	0
Screen sized text	84	46	18	18	0
Multiple arcs	31	33	6	6	0
Containers	4	37	0	0	0
Containers with overlay	89	22	41	41	0
Containers with opa	14	38	1	1	0
Containers with opa_layer	6	36	1	1	0
Containers with scrolling	47	48	12	12	0
Widgets demo	68	40	15	15	0
All scenes avg.	24	37	6	6	0

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.

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[Copilot]

Pull request overview

Fixes slider drag behavior so knob/value updates continue while dragging even when the active input device reports a non-NULL scroll object, matching the documented “continuous update during drag” expectation.

Changes:

• Update update_knob_pos() to ignore lv_indev_get_scroll_obj() when the slider is already in dragging mode.

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[Copilot]

This change alters behavior when indev->pointer.scroll_obj is non-NULL during an active drag, but there’s no automated coverage for this regression scenario. Consider adding a unit test in tests/src/test_cases/widgets/test_slider.c that starts a pointer drag, then (e.g. via an LV_EVENT_PRESSING | LV_EVENT_PREPROCESS callback) forces lv_indev_active()->pointer.scroll_obj non-NULL while slider->dragging is true, and asserts that the slider value continues updating / LV_EVENT_VALUE_CHANGED still fires.