Reposting here what i wrote in "Known Issues": https://touchgfx.zendesk.com/hc/en-us/articles/207507415
TextArea and ChromART (DMA2D)
Rendering of TextAreas with ChromART (when TextArea is the top most element / last to be drawn) causes a premature unlocking of the framebuffer and subsequently a premature completion/transfer of the current frame to the display.
Once endFrame() is called by TouchGFX all drawing operations, including DMA operations, should already be completed. Due to a breach of contract by TextArea in how to appropriately protect the framebuffer, DMA operations are allowed to continue even after returning from endFrame().
The contract for a widget is to either:
- Lock the framebuffer (returns a pointer to framebuffer).
- Draw something in the framebuffer.
- Unlock the framebuffer.
Or to use DMA operations, in which case syncronization of the framebuffer is handled automatically.
TextArea, in 4.10.0, mixes the two procedures which can cause glitches if it is the top most element (last to be drawn) of the current screen. The bug can be fixed by manually guarding endFrame() with the following override of endFrame() (based on F4 HAL). It ensures that endFrame() does not return if ChromART operations are still being processed.
void STM32F4HAL::endFrame()
{
if (dma.isDMARunning())
{
OSWrappers::tryTakeFrameBufferSemaphore();
}
HAL::endFrame();
}
/Martin
