How to select nothing by clicking the empty background?

Question

I have a Virtual Treeview (e.g. 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;

I was struggling to figure out the same thing on VST. – Jerry Dodge Mar 22 '19 at 13:42 — Jerry Dodge, Mar 22 '19 at 13:42

score 1 · Answer 1 · answered Mar 22 '19 at 14:31

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;

answered Mar 22 '19 at 14:31

Joachim Marder

782
5
12

1

It wreaks havoc with `toRightClickSelect`. It's one of those hacks that probably leads to chasing down edge-cases forever. Also, i assume you mean *"`toMultiSelect` is not set in **TreeOptions.SelectionOptions**"* (because using `toMultiSelect` means you don't have to do anything special - clicking the empty background unselects already) – Ian Boyd Mar 22 '19 at 14:51
_"because using toMultiSelect means you don't have to do anything special"_ That's what I meant with it works out-of-the-box. – Joachim Marder Mar 22 '19 at 20:53
Yes, the right click selection behavior seems to be a critical point in every TreeView control. Feel free to submit more details in an issue at GitHub. – Joachim Marder Mar 22 '19 at 21:00

Triber · Answer 2 · 2019-03-25T08:11:40.670

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;

How to select nothing by clicking the empty background?

2 Answers2