glitches in qt4 apps

Bug #295079 reported by mhinsch on 2008-11-07
Affects Status Importance Assigned to Milestone
qt4-x11 (Ubuntu)

Bug Description

Binary package hint: libqtgui4

All of this applies to Ubuntu 8.10.

Several qt4 apps show graphical glitches:

- The highlight of menu items which follows the mouse pointer lags behind so that multiple menu items are highlighted (and sometimes not even the one currently selected). This occurs for example in KJots and Kate. Interestingly as well in Mathematica although it comes with its own version of Qt4.

- When changing selection in treewidgets sometimes the displayed selection state gets out of sync with the actual selection. That is, either multiple items or not the one actually selected are highlighted (KJots).

Some additional information:

- I could observe the problems only when running the programs in question in gnome/compiz, under kde4 everything seems to work fine.

- A simple redisplay of the app (e.g. when switching to a different desktop and back) brings it back into a sane state.

- In my own program (a tiny kjots clone) written in qtruby the second problem becomes so bad that the program basically is unusable. It turns out that the likelihood of displayed and internal state in TreeWidget getting out of sync depends somehow on the timing of events. I catch the signal emitted when the selection in the TreeWidget changes to update a TextWidget. The more stuff is done during processing that event the more likely it is that the visual update is skipped.

mhinsch (hinsch-martin) wrote :

There is another similar effect which I just thought might be related. Basically the same thing happens in gnome-terminal. I.e. output of programs, for example 'ls' or just paging a file with 'less' sometimes fails to update the display (see screenshot). As with the qt problem it's just the display, i.e. after switching back and forth one Desktop it looks fine again.
Just for the sake of completeness: the system is running on a Lenovo R61 with NVidia Quadro video card.

mhinsch (hinsch-martin) wrote :

Just a quick update. The same problem occurs (after a while) when editing text in kate. The cursor disappears and changes are not shown. Forcing a redraw shows the correct state.

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