TTrayicon shows wrong (self painted) icon

[Germo]

In my app I use a Trayicon, and to make it clear that there is some action needed i want the image on the Trayicon to display a number.
Creating this image and assigning it to the icon works most of the time. But sometimes there is a wrong number displayed. A number that has already been shown before.

I have been searching for some time now, but i can't seem to find a solution. Anyone here can point me in the right direction?


I created a small test program to display this behaviour.
It has an Image1 that is the default (numberless) icon, and a Image2 that is a faded version of Image1
I binded some click events to ClickVoorGetal procedure.

I am using: Free Pascal Compiler version 3.2.2-r0d122c49 [2024/02/09] for x86_64 on Ubuntu 22.04.5

Code: Pascal  [Select][+][-]

1. Unit unittesticon;
2. {$mode objfpc}{$H+}
3. Interface
4. Uses
5.   Classes, Sysutils, Forms, Controls, Graphics, Dialogs, Menus, ExtCtrls,
6.   StdCtrls;
7.  
8. Type
9.   { TTestForm }
10.   TTestForm = Class(Tform)
11.     Image1 : Timage;
12.     Image2 : Timage;
13.     Listbox : Tlistbox;
14.     Trayicon : Ttrayicon;
15.       PuM_TrayIcon : Tpopupmenu;
16.         Menuitem1 : Tmenuitem;
17.       Menuitem2 : Tmenuitem;
18.     Procedure ClickVoorGetal(Sender : Tobject);
19.   Public
20.     Getal : Integer;
21.     Procedure UpdateTrayIcon;
22.   End;
23.  
24. Var
25.   TestForm : TTestForm;
26.  
27. Implementation
28. {$R *.lfm}
29.  
30. { TTestForm }
31. Procedure TTestForm.ClickVoorGetal(Sender : Tobject);
32. Begin
33.   Getal := Random(1000);
34.   Caption := IntToStr(Getal);
35.   Listbox.Items.Add(IntToStr(Getal));
36.   ListBox.Invalidate;
37.   UpdateTrayIcon;
38.   End;
39.  
40. Procedure TTestForm.Updatetrayicon;
41. // Function to create an icon with a number on it
42. Function NewIcon(Aantal : Integer) : TIcon;
43. Var
44.   WorkBitmap : TBitMap = nil;  // Bitmap for creating Image
45.   CountText : String = '';     // text to display
46.   DesiredWidth,                // optimal width
47.   CountTextWidth,              // width after font adjust
48.   CountTextHeight,             // height after font adjust
49.   WidthOfset,                  // h-ofset to place text in center
50.   HeightOfset : Integer;       // v-ofset to place text in center
51. Begin
52.   Result := TIcon.Create;      // we have to return an icon
53.   If Aantal = 0 Then Begin     // Default image as result
54.     Result.Assign(Image1.Picture.Bitmap);  // standaard icoon
55.     End
56.   Else Begin                   // we create our own image
57.     WorkBitmap := TBitmap.Create;  // create a WorkBitmap
58.     Try
59.       WorkBitmap.Assign(Image2.Picture.Bitmap);  // faded icoon as base
60.       WorkBitmap.Canvas.Brush.Style := bsClear;  // no background with text
61.       WorkBitmap.Canvas.font.name := 'FreeSans'; // font settings
62.       WorkBitmap.Canvas.font.Bold := True;
63.       WorkBitmap.Canvas.font.Size := 60;
64.       CountText := Format('%d',[Aantal]);      // text we want to display
65. // we want the text to fill 80% of the icon
66.       DesiredWidth := Trunc(WorkBitmap.Width * 0.8);
67. // while text is to small => increase font size
68.       While (WorkBitmap.Canvas.TextWidth(CountText) < DesiredWidth) And
69.             (WorkBitmap.Canvas.TextHeight(CountText) < DesiredWidth) Do
70.         WorkBitmap.Canvas.font.size := WorkBitmap.Canvas.font.size + 2;
71. // in case the text is to big => decrease font size
72.       While (WorkBitmap.Canvas.TextWidth(CountText) > DesiredWidth) And
73.             (WorkBitmap.Canvas.TextHeight(CountText) > DesiredWidth) And
74.             (WorkBitmap.Canvas.font.size > 10) Do
75.         WorkBitmap.Canvas.font.size := WorkBitmap.Canvas.font.size - 2;
76. // calculate position
77.       CountTextWidth := WorkBitmap.Canvas.TextWidth(CountText);
78.       CountTextHeight := WorkBitmap.Canvas.TextHeight(CountText);
79.       WidthOfset := (WorkBitmap.Width - CountTextWidth) Div 2;
80.       HeightOfset := (WorkBitmap.Height - CountTextHeight) div 2;
81. // draw text (a little to the topleft) in white
82.       WorkBitmap.Canvas.font.color := clWhite;
83.       WorkBitmap.Canvas.TextOut(WidthOfset-8,HeightOfset-8,CountText);
84. // draw text (a little to the bottomright) in black
85.       WorkBitmap.Canvas.font.color := clBlack;
86.       WorkBitmap.Canvas.TextOut(WidthOfset+8,HeightOfset+8,CountText);
87. // draw the text in red
88.       WorkBitmap.Canvas.font.color := clRed;
89.       WorkBitmap.Canvas.TextOut(WidthOfset,HeightOfset,CountText);
90. // assign the resulting (bitmap) to our function-return
91.       Result.Assign(WorkBitmap);
92.     finally
93. // cleanup our working bitmap
94.       FreeAndNil(WorkBitmap);
95.       End;
96.     End;
97.   End;
98.  
99. Var
100.   NumberIcon : TICon;
101. begin
102. // check-text in menuitem-caption
103.   Menuitem2.Caption := Format('Aantal = %d',[Getal]);
104. // create a new icon with a number
105.   NumberIcon := newicon(Getal);
106.   Try
107. // clear the icon in the trayicon
108.     TrayIcon.Icon.Clear;
109. // assign our newly created icon
110.     TrayIcon.Icon.Assign(NumberIcon);
111. // let TrayIcon update itself
112.     TrayIcon.InternalUpdate;
113.   Finally
114. // cleanup our working icon
115.     FreeandNil(NumberIcon);
116.     End;
117.   end;
118.  
119. End.
120.