[Konsole-devel] [Bug 98410] New: scrolling slow after showing some japanese characters

[Eduardo Habkost]

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http://bugs.kde.org/show_bug.cgi?id=98410         
           Summary: scrolling slow after showing some japanese characters
           Product: konsole
           Version: unspecified
          Platform: Conectiva RPMs
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: konsole-devel kde org
        ReportedBy: ehabkost conectiva com br


Version:           1.5 beta (using KDE KDE 3.3.91)
Installed from:    Conectiva RPMs
OS:                Linux

I've enabled unicode on konsole recently, and during my tests, konsole became too slow to draw the screen. If I run some application with lots of output (like 'strace find /'), the screen takes around 0.5 second for each redraw of the screen.

Testing further, I've noticed that it happens only after some wide characters are shown (like japanese chars). Steps to reproduce:

- Start konsole, set encoding to unicode, locale set to pt_BR.UTF-8
- strace find / => drawing ok, fast
- drawing/scrolling is fast for a long time, until a japanese caracter is drawn (e.g. cat some-japanese-text.txt)
- scrolling a single line on the screen become slow. You can see the scren being draw line by line. I have a Celeron 433MHz CPU, but even on a faster machine (1.8GHz) the difference on speed can still be seen
- even after the japanese text is not on the view port anymore, scrolling continues slow
- clearing the history (without any japanese char on the view port), doesn't solve the problem

- Interesting point: The scrolling speed is fast again if I create another shell tab and switch between the tabs (as long as there is not japanese char on the view port of the tab being selected). Speed is restored when switching tabs even if there are japanese chars on the history (but not on the view port), and remains fast until they are drawn on the screen again