The chart does not work correctly on the last commit


hello everyone,
I update the LVGL code, last commit id is 8b1500756
but I think there is some bug, my chart works with the v8.2 tag but this commit doesn’t work correctly I understood in debugging that “LV_EVENT_DRAW_MAIN” event of the chart does not send

What MCU/Processor/Board and compiler are you using?


What LVGL version are you using?

last version


Does you chart have any parts which are using any level of transparency?

If so it might be worth updating to the latest commit and taking a look at this post from yesterday:

Hope that helps.



thanks pete-pjb
Yes, my chart has some parts that are transparent(lv_opa_0), also I have some problems in the image that I set “transform_zoom”
I did these steps but it did not work
1- git pull LVGL code: my last commit is ff7204eca which is the post you recommend
2- set “LV_COLOR_SCREEN_TRANSP” to 1 in the lvgl.conf


I am sorry that was not helpful, I just saw your post and it seemed it could be related. We will need to ask @kisvegabor if he can comment, the recent updates are extensive and I am not familiar with the code in the area of the update.

It might be worth raising a Github issue also.

Kind Regards,


Thank you for your help.
Does anybody have other suggestions?


Please a send a code snippet to reproduce the issue. There was a large updated related to opacity and transformations so it can happen that something is not perfect yet.

Hello kisvegabor
chart.txt (7.7 KB)

hello @kisvegabor
I think this could be related to the amount of CPU used:
I get the data from a module then I send the data to the chart for drawing in realtime, the chart doesn’t change also the system doesn’t work correctly,
you think the system stopped until I turn off the module and the data sending to the chart is finished, then the chart is drawn according to the last data sended

in brief, I think drawing the chart consumed a lot of CPU that other parts of LVGL cant work

I couldn’t use the attached code because there was a lot of undefined variables and FreeRTOS specific functions. Having a minimal code just to demonstrate problem would be great.

LVGL refreshed the dirty areas sequentially. So the normally the worst thing that can happen is that you will get a low FPS, but not reduced functionality.

Hello @kisvegabor
I updated the LVGL codes today, the chart is drawing in realtime but the CPU used is about 80 percent however CPU used is about 40 percent in the V8.2

ok, I check my code again and I try to simplify it

I simplified the code please check the code:
chart2.txt (6.1 KB)
PS: I couldn’t use the simulator with the latest version of LVGL as I get compile error with lvgl8.3