[Konsole-devel] [Bug 155174] Significant delay when switching tabs

[Eike Hein]

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http://bugs.kde.org/show_bug.cgi?id=155174         




------- Additional Comments From hein kde org  2008-03-17 18:51 -------
Sadly, no. I'm currently using 169.12 and Qt 4.4 Beta 1, and the performance issues with tab switching and Yakuake's animation when using a fixed-width bitmap font remain the same.

However, nVidia has issued[1] an new 171.06 Beta driver on March 7th. Quoting the announcement: 

"Note: This release has experimental support for a glyph cache on the GeForce 8 and 9 series that may improve anti-aliased font rendering performance. Enable with nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1."

The InitialPixmapProperty option of the driver controls where X pixmaps are created and held. The new driver supports a new value '2', which according to the headers is NV_CTRL_INITIAL_PIXMAP_PLACEMENT_VIDMEM, and that new GlyphCache option.

There's a 20+ page thread in then nVidia Linux driver forums[2] where KDE users have complained about shoddy rendering performance of anti-aliased text in KDE apps for years. It can be so bad with certain GPUs, I've seen videos where one can comfortably follow how individual lines in Kate are drawn. In general, it tends to be slower than pure VESA. This driver release appears to try and address that issue by trying harder to cache glyphs in video memory, avoiding costly roundtrips[3]. Reaction on the forums seems to be positive.

There's a number of parallels between the problem we're dealing with here and that story: Konsole, of course, deals in glyphs. Glyphs get drawn through XRender. The XRender software implementation (as used by Xephyr) being faster than the driver. And so on. Thus I'm hoping that this new beta driver might resolve this issue as well, but I haven't had a chance to test it yet unfortunately.

1 = http://www.nvnews.net/vbulletin/showthread.php?t=109422
2 = http://www.nvnews.net/vbulletin/showthread.php?t=65857
3 = http://www.nvnews.net/vbulletin/showthread.php?t=109478