Reducing the Drawbuffer res in Pi4

[Brian Beuken]

There was a really nice trick on the broadcom VC IV Pi's which allowed me to have a full screen display, but reduce the resolution of the render buffers by halving or quartering the src_rect and using a viewpoint that size.

Code: Select all

	dest_rect.width = width; // it needs to know our window size
	dest_rect.height = height; //

	src_rect.x = 0;
	src_rect.y = 0;
	src_rect.width = (FBResX) << 16; // FBRRes is 1/4 width/heigh for zero, 1/3 for 1A, and  2/3 for 2 and 3B and 3B+
	src_rect.height = (FBResY) << 16;

This was handy for rendering to the Zero/1 which are much lower power than the 2/3's which I usually set to half size, the Pi4 despite a bit more oomph, is not quite capable of rendering my demo's at 60hz at 1080p so I'd like to try and half the size again.

But I don't know how to do that on an X11 window setup, since it does not expose the same values, is it possible to set a renderbuffer to half size but have Xwindow scale to full size?