LCA: The ways of Wayland

LCA: The ways of Wayland

Posted Mar 18, 2013 10:24 UTC (Mon) by nix (subscriber, #2304)
In reply to: LCA: The ways of Wayland by Cyberax
Parent article: LCA: The ways of Wayland

Something that doesn't really exist. Modern videocards don't have any intrinsic way to accelerate drawing of thick lines (especially with antialiasing), so X-server has to do it in software. Of course, thick lines and everything else can be emulated in shaders but as far as I know, no driver in X.org does this.

There's a reason for that. It's pointless. Almost no applications draw thick lines anymore, just as almost no applications use the ROPpery in the core protocol.

TBH, while it would be nice for my BARTS Radeon card here to have XRender acceleration as good as my old Matrox had, it's also pointless: the card is so fast that except in its lowest-power mode a full-screen refresh of two 1680x1050 monitors filled with tiny text composited onto a bitmap backdrop is instantaneous (I clocked it at 35fps in medium-performance mode, 60fps in high). Visible latencies happen only if the glyph cache fills up -- which hardly ever happens these days, I notice it once every few months -- and that's a latency imposed by the sloth of moving data into the GPU, which can hardly be fixed by ditching XRender's glyph caching and moving even more data across the bus.

You appear to be saying that XRender should be killed with fire because it can't be accelerated, even though I would require a prosthetic visual cortex to see the results of any such acceleration, and even though the only thing you've recommended replacing it with would exacerbate the only thing left in XRender that ever causes visible delays in my experience. Thanks, but no thanks.

>Third, that's not a limitation of X11 protocol, you know?

It is. There is exactly ONE implementation of X protocol with XRender extension.

You clearly didn't understand Serge's point. The protocol does not mandate lack of acceleration: indeed, in the past, at least one driver has implemented it. So the current ONE implementation does not make it impossible to accelerate XRender. (In fact, one of the problems with XRender is that it needs too much support code inside the drivers. If there was "ONE implementation" this would actually be better than what we have now.)

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