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How to scroll a TForm through code Turn on/off line numbers in source code. Switch to Orginial background IDE or DSP color Comment or reply to this aritlce/tip for discussion. Bookmark this article to my favorite article(s). Print this article
28-Oct-02
Category
VCL-Forms
Language
Delphi 2.x
Views
112
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Publisher:
DSP, Administrator
Reference URL:
DKB
			Author: Jonas Bilinkevicius

I'm using a form with a TPaintBox element that exceeds the size of the form, so the 
form has two scrollbars. I want the user to be able to scroll the form using the 
keyboard (with cursor keys). How can I perform scrolling programmatically? I tried 
using the TForm.ScrollBy method, but the results are a bit strange.

Answer:

Do not use ScrollBy, instead send WM_VSCROLL messages to the form to make it do the 
work for you.
1   
2   procedure TfrmMain.FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
3   begin
4     case Key of
5       VK_DOWN: {scroll down}
6         begin
7           Perform(WM_VSCROLL, SB_LINEDOWN, 0);
8           Perform(WM_VSCROLL, SB_ENDSCROLL, 0);
9         end;
10      VK_UP: {scroll up}
11        begin
12          Perform(WM_VSCROLL, SB_LINEUP, 0);
13          Perform(WM_VSCROLL, SB_ENDSCROLL, 0);
14        end;
15    end;
16  end;


If you use ScrollBy you also have to manually adjust the scrollbar position since it only scrolls the windows client area, completely independent of any scrollbar.

			
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