Partial framebuffer clears in OpenGL

I've stumbled upon a question in your forum related with what I want to achieve and would like to check if it could be used for my purpose. In my case I'm looking into rendering parts of the framebuffer at a different frequency, while preserving other parts (which shouldn't change across frames). So, ideally, I'd like to perform clears in specific areas to achieve that. Am I right in assuming that if do the following I'll be able to preserve partial framebuffer contents on Mali GPUs? So, the intention being to tell the driver I want to invalidate the "custom area" and the proceed with a clear and draw to the remaining areas.

// FRAME 1


// draw everything needed

// FRAME 2-N
glScissor(fromX, fromY, custom_area_width, custom_area_height);
glScissor(0, 0, fbo_width, fbo_height); // full screen

// draw only I care about outside the custom area

I'm aware of transaction elimination, but I'd like to (a) completely avoid rendering to areas I know are not changing and (b) preserve those across frames if possible.


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