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Scroll in TreeView components

Posted on 2003-10-30
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Last Modified: 2010-04-05
I have a TreeView (in a Delphi 7 program) and one of the operations I want supported is to "Move" elements between nodes. The problem is that when I'm dragging an element and the target node is out of sight the view does not scroll down to show the other elements.

How can I add scroll up and down when the cursor gets out of the control's boundaries ?

Thanks in advance !


AJ
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Question by:ajgonzalezm
4 Comments
 
LVL 5

Accepted Solution

by:
snehanshu earned 50 total points
ID: 9654776
Does this help?
(Changing Drag-Over event of the TreeView);

procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
begin
   // draggin over
  if (Sender is TForm) and (Source is TTreeView) then
    begin
    with Source as TTreeView do
        // check if we are in the hot zone (in this case only above or below)
      if (x > Left) and (x < Left + Width) and
         (y > Top - HOTZONE_WIDTH) and (y < Top + Height + HOTZONE_WIDTH)
        then begin
          Accept := true;  // we could set false here, too.
          if y < Top
            then Perform(WM_VSCROLL, SB_LINEUP, 0)
            else Perform(WM_VSCROLL, SB_LINEDOWN, 0);
          end
        else Accept := false;
    end
  else
    Accept := (Sender = Source);
end;

I picked this up from
http://www.experts-exchange.com/Programming/Programming_Languages/Delphi/Q_10125137.html?query=TreeView+Scroll&searchType=topic

HTH,
...Snehanshu
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LVL 27

Assisted Solution

by:kretzschmar
kretzschmar earned 50 total points
ID: 9677227
well, another method

procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
var ANode : TTreeNode;
begin
  ANode := TreeView1.GetNodeAt(x,y);
  Accept := assigned(ANode); //just as sample
  //Scrolling needed ?
  if ((y < 9) or
     (y > TreeView1.Height - 9)) and
     (assigned(ANode)) then
    //ScrollUp ?
    if (y < 5) then
      ANode := ANode.getPrevSibling
    else
      ANode := ANode.getNextSibling;
  If assigned(ANode) then
    ANode.MakeVisible;
end;

meikl ;-)
0

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