Graphics stack: Difference between revisions

The compositor is the part that combines the individual elements being rendered into the instantaneous display state, that is, the screen as it is at a given moment. In a 2-D design, this is usually done by the renderer directly, but 3-D UIs almost always have a separate compositor.

 

OK, quick history lesson. Early 2-D windowing systems generally composited in situ, that is, directly into the display. However, while this was feasible with the stroke-vector displays of the 1960s, or on raster displays that used fixed cells drawn from tables of glyphs such as PLATO and the majority of text-oriented terminals, this was problematic for bitmapped video systems even from the outset, as it meant that a large block of memory - often as much as 30% of system memory in the days of the Alto and 128K Macintosh had to be set aside for the video, and the timing of drawing had to be synced with the vertical refresh in order to avoid flicker.