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Lazarus – TTreeview – Prevent popup menu when not clicking a node

Lazarus – TTreeview – Prevent popup menu when not clicking a node

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Home Forums Software Development Delphi, Lazarus, Free Pascal Lazarus – TTreeview – Prevent popup menu when not clicking a node

This topic contains 0 replies, has 1 voice, and was last updated by  hans 2 months, 1 week ago.

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    hans
    Keymaster

    While working on ApplePi-Baker v2, I ran into an issue with TTreeView.

    When right clicking the TreeView, I wanted to display a popup menu, based on the selected node (ttreeview.multiselect = false).
    To my surprise, TTreeView doesn’t really seem to care if you’re right clicking a node or not.
    So right clicking in blank space (no node under the mouse cursor) actually does popup the menu, and I couldn’t find an easy and reliable way to determine if the mouse was (still) over a node of the treeview.

    The trick is to prevent the popup menu from appearing when the mouse cursor is not over a node and this can be done with the OnContextPopup event.
    The OnContextPopup event has a “Handled” variable. If set to TRUE, Treeview considers the context action to be done and dealt with.
    This event also passes the mouse cursor position, so we can use GetNodeAt() to determine what node the mouse cursor was clicking.

    All combined in simple code:

    procedure TForm1.TreeviewContextPopup(Sender: TObject; MousePos: TPoint; var Handled: Boolean);
    begin
      if Treeview.GetNodeAt(MousePos.X, MousePos.Y) = nil then
        Handled := True;
    end;   
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