How to disable MouseWheel if mouse is not over VirtualTreeView (TVirtualStringTree)
TVirtualStringTree behaves by default if it is focused - it will scroll on mouse wheel even if mouse is not over control (except if it is over another TVirtualStringTree).
Is there a quick and elegant way to disable this behaviour?
I already did this with OnMouseWheel event and checking with PtInRect if Mouse.CursorPos if it is over a control but I have a feeling that there is a better way to do the same because this way I'd have to define a new event for each TreeView I add and also handle when to focus/unfocus the control so I hope there must be a better way to disable this.
So to be clear, I want mousewheel function to work as usual, but only when mouse is over VirtualTreeView.
Drop down a TApplicationEvents control to the form
in TApplicationEvents onMessage
procedure TForm5.ApplicationEvents1Message(var Msg: tagMSG; var Handled: Boolean); var pnt: TPoint; ctrl: TWinControl; begin if Msg.message = WM_MOUSEWHEEL then begin if not GetCursorPos(pnt) then Exit; ctrl := FindVCLWindow(pnt); if Assigned(ctrl) then Msg.hwnd := ctrl.Handle; end; end;
Or you might try to modify the VirtualTree a bit. In the following example is used the interposed class. If you paste this code into your unit, then all of your VirtualTrees will behave this way in the form.
uses VirtualTrees; type TVirtualStringTree = class(VirtualTrees.TVirtualStringTree) private FMouseInside: Boolean; procedure CMMouseEnter(var Message: TMessage); message CM_MOUSEENTER; procedure CMMouseLeave(var Message: TMessage); message CM_MOUSELEAVE; procedure CMMouseWheel(var Message: TCMMouseWheel); message CM_MOUSEWHEEL; end; implementation procedure TVirtualStringTree.CMMouseEnter(var Message: TMessage); begin inherited; // SetFocus will set the focus to the tree which is entered by mouse // but it's probably what you don't want to, if so, just remove the // following line. If you want to scroll the tree under mouse without // stealing the focus from the previous control then this is not the // right way - the tree must either be focused or you can steal it by // the SetFocus. This only resolves the case when you have a focused // tree and leave it with the mouse, then no scrolling is performed, // if you enter it, you can scroll again. SetFocus; // set the flag which tells about mouse inside FMouseInside := True; end; procedure TVirtualStringTree.CMMouseLeave(var Message: TMessage); begin // reset the flag about mouse inside FMouseInside := False; inherited; end; procedure TVirtualStringTree.CMMouseWheel(var Message: TCMMouseWheel); begin // if mouse is inside then let's wheel the mouse otherwise nothing if FMouseInside then inherited; end;