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Why can't I draw an outline around my TLabel?

Posted on 2004-10-03
6
327 Views
Last Modified: 2010-04-05
Hi,
Take a look at the code below.

The code in the Shape1DragDrop event handler FAILS to create a dotted outline around the TLabel which is  created firstly in this procedure.

BUT....the same two lines of code dropped into the Button1Click event handler below DOES create the outline around the same label!

Any ideas why this is??
I don't want the user to have to click a button to draw the outline around this label :)

Thanks

procedure TForm1.Shape1DragDrop(Sender, Source: TObject; X, Y: Integer);
begin
if Source is TListBox then
begin
  l := TLabel.Create(Self);
  l.Left := X;
  l.Top := Y;
  l.Parent := Panel1;
  l.Caption := ListBox1.Items[ListBox1.ItemIndex];
  l.Canvas.Pen.Style := psDot;
  l.Canvas.Rectangle(0,0,l.Width,l.Height);
  MyArray[1] := l;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  l.Canvas.Pen.Style := psDot;
  l.Canvas.Rectangle(0,0,l.Width,l.Height);
end
0
Comment
Question by:nathc
  • 3
  • 2
6 Comments
 
LVL 4

Expert Comment

by:mottor
ID: 12211113
Because changing caption requires repaint:
...
.......
    l.Caption := ListBox1.Items[ListBox1.ItemIndex];
    l.Canvas.Pen.Style := psDot;
    Panel1.Repaint;                                     //  Look here
    l.Canvas.Rectangle(0,0,l.Width,l.Height);
....
0
 

Author Comment

by:nathc
ID: 12211160
Thanks mottor, that worked but raised a new issue.
The first label dropped onto Shape1 works fine but when I drop the second one on the dashed border around the first label disappears.
Is this something to do with the repaint??
0
 
LVL 6

Expert Comment

by:Jaymol
ID: 12211258
The repaint will only do what it thinks it should do, and that is to redraw every object as it should be.  If you have made any manual changes (eg. drawing directly onto the canvas) then these changes will be lost as they are not actually part of the object.

You will need to redraw any manual canvas changes after every repaint.
0
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LVL 4

Accepted Solution

by:
mottor earned 125 total points
ID: 12211330
Add this to your code and use TMyLabel instead of TLabel :

type TMyLabel = class(TLabel)
     protected
       procedure Paint; override;
     end;
procedure TMyLabel.Paint;
begin
  inherited;
  Canvas.Pen.Style := psDot;
  Canvas.Rectangle(0,0,Width,Height);
end;

0
 

Author Comment

by:nathc
ID: 12213964
Hey Mottor,

I get this error
[Error] LabelCreate.pas(42): Identifier redeclared: 'TMyLabel.Paint'
[Error] LabelCreate.pas(43): This form of method call only allowed in methods of derived types

When I try the code below.

type TMyLabel = class(TLabel)
     protected
       procedure Paint; override;
     end;
-->procedure TMyLabel.Paint; <--- This line!!
begin
  inherited;
  Canvas.Pen.Style := psDot;
  Canvas.Rectangle(0,0,Width,Height);
end;

Any ideas??
0
 

Author Comment

by:nathc
ID: 12214249
Sorry mottor, got it working. Just shifted the procedure bit elsewhere thanks very much :)
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