TVirtualTreeView with rows of variable height: scrolling artefacts

Question

I am using the VirtualTreeView together with the OnMeasureItem event to display rows of variable size. The problem is that the event seems to be called only if a row is painted (following the virtual paradigm). But this leads to the scrollbar being displayed incorrectly. If I scroll to the bottom (by dragging the scrollbox with the mouse, not clicking the scroll buttons at the top or bottom), not the last row is displayed (which is what I would expect), but some row in the middle. After that, the scrollbar is updated and I can scroll further down. It seems as if the component uses the DefaultNodeHeight for its scrolling calculations. But since my rows have variable height, I cannot specify a DefaultNodeHeight that would lead to correct results. Option toVariableNodeHeight is enabled.

Has anyone experienced this before and maybe found a workaround? Or am I doing it wrong?

Just for sure. Do you have `toVariableNodeHeight` option included in the `TreeOptions.MiscOptions` set, do you ? Could you include this information into your question as well as the version of VirtualTreeView are you using, please ? — TLama, Mar 05 '13 at 12:23
`toVariableNodeHeight` makes no difference - I tried both. I am on revision 431 which is from november 2012. — jpfollenius, Mar 05 '13 at 12:40

score 4 · Accepted Answer · edited May 23 '17 at 12:31

4

You need to set DefaultNodeHeight to the maximum value you will be using and OnMeasureItem event set custom height value for the current node. Similar issue was described here.

edited May 23 '17 at 12:31

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answered Mar 05 '13 at 15:47

Linas

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Thank you very much!! I just set it to some upper bound value and it works perfectly. – jpfollenius Mar 07 '13 at 07:51

TVirtualTreeView with rows of variable height: scrolling artefacts

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