[Lazarus] Mouse wheel problem

Fabio Luis Girardi fluisgirardi at gmail.com
Tue Sep 18 16:27:15 CEST 2018

Hi all!

I'm experiencing a problem with the mouse wheel and combobox control. I
have a big form (4900x1000) on a single monitor. I put this big form on a
Scrollbox to make it scrollable. To make the things easy to user/system
operator, I decided to move the screen using the mouse wheel. This works
fine and makes the navigation on this screen/form easy.

The problem appears when the mouse cursor stops (after mouse wheel) over a
combobox control. Even the combobox over the mouse cursor doesn't have the
focus, the next mouse wheel event doesn't move the screen, but changes the
combobox selection.

All combobox on my application has Style set to csDropDownList. Another
point that I noted, is that mouse wheel change doesn't occur if ItemIndex =

The same behavior is in GTK2 and QT4. I don't have tried on QT5.

Someone knows how workaround or fix this?

The best regards,

Fabio Luis Girardi
PascalSCADA Project
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