Mega Code Archive
How to scroll a Treeview when DragDrop
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Title: How to scroll a Treeview when Drag/Drop
procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin
if (y 15) then {On the upper edge - should scroll up }
SendMessage(TreeView1.Handle, WM_VSCROLL, SB_LINEUP, 0)
else if (TreeView1.Height - y 15) then { On the lower edge - should scroll down }
SendMessage(TreeView1.Handle, WM_VSCROLL, SB_LINEDOWN, 0);
end;
{+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
ERWEITERUNG von / ENHANCEMENT sent by
Stef Mientki (http://Punthoofd.flappie.nl)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++}
{
Thomas Stutz wrote a code snippet, to scroll a treeview,
when dragging near top/bottom of a treeview.
But with his code, you had to keep your mouse moving.
Adding a timer, does the work for you.
}
....
private
{ Private declarations }
scroll_down :boolean;
....
procedure TForm_test_list.tv_filesDragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
(*******************************************************************************
Start auto scroll when draging near top or bottom
*******************************************************************************)
begin
if y<15 then
begin
scroll_down:=true;
timer_autoscroll.Enabled:=true;
end
else
if (list.Height-y)<15 then
begin
scroll_down:=false;
timer_autoscroll.Enabled:=true;
end
else timer_autoscroll.Enabled:=false;
end;
procedure TForm_test_list.Timer_autoscrollTimer(Sender: TObject);
(*******************************************************************************
Set timer to about 100 msec (disabled at initialization)
*******************************************************************************)
begin
if scroll_down then
SendMessage(tv_files.Handle, WM_VSCROLL, SB_LINEUP, 0)
else
SendMessage(tv_files.Handle, WM_VSCROLL, SB_LINEDOWN, 0);
end;
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