Override TPanel.OnPaint - but Children no longer show?

[Ozz_Nixon]

I have successfully modified TPanel's OnPaint to give me a gradient background.


However, the children (a TLabel and a TImage) no longer render. I am assuming that I am supposed to crawl the Components[index] and call Paint or Invalidate? Or is it because I do not have inherited OnPaint; in my onPaint code? 


I am simply calling the GradientFill(Rect,StartColor,EndColor,Vert);


** PART TWO of this question - is it possible to treat the Fill like a roundRect?

[Handoko]

For your information, OnPaint event and Paint method are 2 different things. Because you mentioned OnPaint several times, so I tested it on my Lazarus 2.2.6 Ubuntu, it worked.

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls, StdCtrls;
9.  
10. type
11.  
12.   { TForm1 }
13.  
14.   TForm1 = class(TForm)
15.     Image1: TImage;
16.     Label1: TLabel;
17.     Panel1: TPanel;
18.     procedure FormCreate(Sender: TObject);
19.   private
20.     procedure NewPanelPaint(Sender: TObject);
21.   public
22.  
23.   end;
24.  
25. var
26.   Form1: TForm1;
27.  
28. implementation
29.  
30. {$R *.lfm}
31.  
32. { TForm1 }
33.  
34. procedure TForm1.FormCreate(Sender: TObject);
35. begin
36.   Label1.Caption := 'Test custom OnPaint';
37.   Panel1.OnPaint := @NewPanelPaint;
38. end;
39.  
40. procedure TForm1.NewPanelPaint(Sender: TObject);
41. begin
42.   Panel1.Canvas.GradientFill(Panel1.ClientRect, clWhite, clYellow, gdVertical);
43. end;
44.  
45. end.

For gradient round rectangle, you can try:
https://forum.lazarus.freepascal.org/index.php/topic,32677.msg210848.html#msg210848

[lainz]

I have successfully modified TPanel's OnPaint to give me a gradient background.


However, the children (a TLabel and a TImage) no longer render. I am assuming that I am supposed to crawl the Components[index] and call Paint or Invalidate? Or is it because I do not have inherited OnPaint; in my onPaint code? 


I am simply calling the GradientFill(Rect,StartColor,EndColor,Vert);


** PART TWO of this question - is it possible to treat the Fill like a roundRect?

You need to call inherited.

For your information, OnPaint event and Paint method are 2 different things. Because you mentioned OnPaint several times, so I tested it on my Lazarus 2.2.6 Ubuntu, it worked.

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls, StdCtrls;
9.  
10. type
11.  
12.   { TForm1 }
13.  
14.   TForm1 = class(TForm)
15.     Image1: TImage;
16.     Label1: TLabel;
17.     Panel1: TPanel;
18.     procedure FormCreate(Sender: TObject);
19.   private
20.     procedure NewPanelPaint(Sender: TObject);
21.   public
22.  
23.   end;
24.  
25. var
26.   Form1: TForm1;
27.  
28. implementation
29.  
30. {$R *.lfm}
31.  
32. { TForm1 }
33.  
34. procedure TForm1.FormCreate(Sender: TObject);
35. begin
36.   Label1.Caption := 'Test custom OnPaint';
37.   Panel1.OnPaint := @NewPanelPaint;
38. end;
39.  
40. procedure TForm1.NewPanelPaint(Sender: TObject);
41. begin
42.   Panel1.Canvas.GradientFill(Panel1.ClientRect, clWhite, clYellow, gdVertical);
43. end;
44.  
45. end.

For gradient round rectangle, you can try:
https://forum.lazarus.freepascal.org/index.php/topic,32677.msg210848.html#msg210848

The author of this topic is talking about overriding not using the event.

[wp]

** PART TWO of this question - is it possible to treat the Fill like a roundRect?

Use a clip region:

Code: Pascal  [Select][+][-]

1. uses
2.   LCLIntf, LCLType;
3.  
4. procedure TForm1.Panel1Paint(Sender: TObject);
5. var
6.   Rgn: HRgn;
7. begin
8.   Rgn := CreateRoundRectRgn(0, 0, Panel1.Width, Panel1.Height, 30, 30);
9.   try
10.     SelectClipRgn(Panel1.Canvas.Handle, Rgn);
11.     Panel1.Canvas.GradientFill(Rect(0, 0, Panel1.Width, Panel1.Height), clBlue, clSkyBlue, gdVertical);
12.     SelectClipRgn(Panel1.Canvas.Handle, 0);
13.   finally
14.     DeleteObject(Rgn);
15.   end;
16. end;