rlottie animations not running as fast as they should

[stwirth]

LVGL version

8.3

What happened?

When an rlottie animation has a higher framerate than the lvgl update rate (frequency of calls to lv_timer_handler) then it runs slower as it should.

How to reproduce?

No response

[stwirth]

The next frame callback is initialized using the frame rate specified in the lottie:

lvgl/src/extra/libs/rlottie/lv_rlottie.c

Line 148 in 36a8052

rlottie->task = lv_timer_create(next_frame_task_cb, 1000 / rlottie->framerate, obj);

and then in the callback, the frame number is simply incremented by 1:

lvgl/src/extra/libs/rlottie/lv_rlottie.c

Lines 253 to 254 in 36a8052

	if(rlottie->current_frame < rlottie->total_frames)
	++rlottie->current_frame;

I think it should instead calculate which frame should be rendered based on the time elapsed.

[kisvegabor]

Hi,

Can you try it this PR? It uses a more recent Lottie implementation and it's also easier to integrate into LVGL.

[stwirth]

Nice development @kisvegabor! Unfortunately I'm still on v8.3 so testing your PR will involve quite a bit of refactoring for me. I'll report back when I get it done.

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