TScrollBox question
Quote
glet...@aol.com (GLetour) wrote:
>I have a drawing pane which is a TScrollBox object. I draw
>on the canvas of this pane with no problem. However, when
>I scroll the pane it doesn't invalidate and redraw the contents.
>That is ok as I want to invoke the drawing myself. Unfortunately,
>I do not see any way to notify myself that a scrollbar OF THE
>SCROLLBOX has been hit. If I had just a scrollbar I would simply
>use the OnScroll event, but the scrollbox does not have a
>corresponding method. How do I see if a scrollbar OF THE
>SCROLLBOX has been hit? By the way, this a Delphi 1.0 program
>compiled under Delphi 1.0.
>Gary Letourneau
>Palet Software, Inc.
>pa...@imssys.com
Try creating a component that is based on the TScrollbox type but
includes an OnScroll event. You will need to provide a property for
the event procedure and respond to the WM_VSCROLL and WM_HSCROLL
messages. The component could look something like:
TNotifyScrollBox = class(TScrollBox)
private
fOnScroll: TScrollEvent;
procedure WMVScroll(var msg: TWMVScroll); message WM_VSCROLL;
procedure WMHScroll(var msg: TWMHScroll); message WM_HSCROLL;
published
OnScroll: TScrollEvent read fOnScroll write fOnScroll;
end;
implementation
procedure TNotifyScrollBox. WMVScroll(var msg: TWMVScroll);
var
code: TScrollCode;
begin
if Assigned(fOnScroll) then begin
code:= TScrollCode(msg.ScrollCode);
fOnScroll(self, code, msg.nPos);
end;
inherited;
end;
procedure TNotifyScrollBox. WMHScroll(var msg: TWMHScroll);
var
code: TScrollCode;
begin
if Assigned(fOnScroll) then begin
code:= TScrollCode(msg.ScrollCode);
fOnScroll(self, code, msg.nPos);
end;
inherited;
end;
Good Luck,
Steve
