如何通过单击空白背景来选择任何内容？

Question

I have a Virtual Treeview (eg TVirtualStringTree ).

• The user can select a row
• but it would be nice if they could also do the intuitiave thing of clicking "nowhere" to select no row

Note: Of course multiselect is off; because they can only select zero or one items

MCRE:

procedure TForm6.FormCreate(Sender: TObject);
var
    vst: TVirtualStringTree;
begin
    vst := VirtualStringTree1;

    vst.RootNodeCount := 5;
    vst.TreeOptions.SelectionOptions := vst.TreeOptions.SelectionOptions + [toFullRowSelect];
    vst.Header.Options := vst.Header.Options + [hoVisible];
    vst.Header.Columns.Add;
    vst.Header.Columns.Add;
    vst.Header.Columns.Add;
    vst.Header.Columns.Add;
    vst.Header.Columns.Add;
end;

Answer 1

This should work out-of-the-box if toAlwaysSelectNode is not set and toMultiSelect is set in TreeOption.SelectionOptions. Tested wit latest source.

In other cases simply call ClearSelection() :

procedure TVisibilityForm.VST2MouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  if TBaseVirtualTree(Sender).GetNodeAt(Point(X, Y)) = nil then
    TBaseVirtualTree(Sender).ClearSelection();
end;

Answer 2

This procedure in OnMouseDown should work regardless of the settings, you just need toRightClickSelect in TreeOptions.SelectionsOptions for right click selection, otherwise it doesn't work properly.

procedure VSTMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  if Button in [mbLeft, mbRight] then
    VST.FocusedNode := VST.GetNodeAt(X, Y);

  if Assigned(VST.FocusedNode) then
    VST.TreeOptions.PaintOptions := VST.TreeOptions.PaintOptions - [toAlwaysHideSelection]
  else
    VST.TreeOptions.PaintOptions := VST.TreeOptions.PaintOptions + [toAlwaysHideSelection];
end;