Vetter: Why no 2D Userspace API in DRM?

Posted Aug 23, 2018 9:08 UTC (Thu) by Sesse (subscriber, #53779)
In reply to: Vetter: Why no 2D Userspace API in DRM? by daniels
Parent article: Vetter: Why no 2D Userspace API in DRM?

I guess we need to talk about what “2D rendering” means first. Nobody really cares about accelerated pretty 2D lines and circles and such these days; it's all about getting an image from A to B, possibly including color conversion and rescaling (it depends a bit).

In this understanding of “2D rendering” 3D engines can and do 2D rendering; your composited desktop (even without wobbly windows) is an example. Quads are rendered as two triangles—that's not a problem at all. But they're not suitable for extremely embedded platforms, since they use more area, gates and power than a pure 2D engine would do.

Vetter: Why no 2D Userspace API in DRM?

Posted Aug 23, 2018 14:17 UTC (Thu) by nim-nim (subscriber, #34454) [Link] (2 responses)

Most people will assume 2D includes text. And text is definitely "lines and circles and curves".

Text is the 2D rendering deal-breaker, unless you restrict yourself to ASCII-only single-size bitmap fonts, that do not work on hidpi screens, and that users loathe.

Even basic video players are increasingly expected to render nice non-pixelated i18n subtitles.

Vetter: Why no 2D Userspace API in DRM?

Posted Aug 23, 2018 15:28 UTC (Thu) by louai (guest, #58033) [Link]

Text rendering happens in two stages:

1) Rendering individual glyphs (usually cached)
2) Putting these glyphs on screen

Either one of those can be accelerated, but generally speaking you get a lot more bang for your buck by making the second step fast. And that second step is really just blitting to screen.

Vetter: Why no 2D Userspace API in DRM?

Posted Aug 23, 2018 18:27 UTC (Thu) by Sesse (subscriber, #53779) [Link]

I doubt most of these devices accelerate glyph rendering. You just render them once and cache them.

They still need to be blit to screen one by one, but then we're back to the “get a rectangle from A to B” land.