Writing directly to the frame buffer is effectively the “CPU rendering” or “software rendering” approach. Most modern GUIs use a compositor, which usually rende

Writing directly to the frame buffer is effectively the “CPU rendering” or “software rendering” approach. Most modern GUIs use a compositor, which usually renders the contents of each window using the CPU to textures stored in VRAM. The GPU then does the actual rendering, sampling the textures drawn by the CPU (the windows) as it fills in the polygons, defined as sets of vertices also defined by the CPU.