Render performance on ESP32 S3

[egast]

Hi,

I am experimenting with running Slint on an ESP32 S3 (no_std). I have followed the instructions in the documentation and I have copied the printerdemo_mcu .slint files so I can test how well the printerdemo runs.
I am able to run the printer demo, but I am a bit disappointed about the performance. The frame rate is low and when I benchmark the render function, a full render (368x448) takes about 210 ms. For smaller (dirty) regions it is faster but still pretty slow, for example drawing a 34x348 (dirty) region takes about 74 ms. I am wondering if this kind of performance is normal and is there a wait to improve the performance?

I am using Slint 1.92 with software rendering (ReusedBuffer) and I let slint render to a Rgb565Pixel frame buffer of 368x448 pixels ( renderer.render(&mut buffer, LCD_WIDTH_RES as usize)).

[aurindam]

There is definitely room for improvement. Here are some key areas to focus on:

• Optimize overdrawing to reduce unnecessary rendering.
• Improve the main rendering loop—there’s likely significant room for gains.
• Utilize the second core for better performance.

We have also identified other issues that need to be addressed for the software renderer: https://github.com/slint-ui/slint/issues?q=is%3Aissue%20state%3Aopen%20software%20renderer%20label%3Aa%3Arenderer-software

The main challenge that we face is balancing between customer-requested features (that gives us much needed cash) and general performance improvements. So far, customers using Slint on ESP32 have GUI that generally feature minimal animations and full-page transitions (so no scrolling) for example https://youtu.be/xPW3XAIU3vQ?feature=shared&t=41

If this topic needs to be addressed urgently, then please reach out to me https://cal.slint.dev/aurindam and we will try to see if/how we can fit this in our roadmap.

In the meanwhile, I will convert this into an issue - #7631