Talk:How to use a TrayIcon

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Linux Problems

DRAFT prior to release of Lazarus 2.0.6


Recently, changes in some Linux Desktops that use Gnome have threatened the TrayIcon Lazarus Component. Apparently driven by concern that the Linux System Tray (of which the TrayIcon is an example) is being used in overly complicated User Interfaces and is too hard to maintain at the Desktop level. Some major players have disabled the System Tray altogether, some have replaced it with a simpler model and some still support it.

Most, if not all distributions that don't use Gnome Shell are not a problem. The Gnome Shell desktops, to be used with Lazarus's TrayIcon all require the Gnome Extension, TopIconsPlus or one of its peers be installed. This introduces some issues -

  • End users are uncomfortable installing these Extensions but its unavoidable if they are using a Gnome distribution.
  • libappindicator3 is used (and may also need be installed) and that provides a limited version of the System Tray, a left click is not passed through to TrayIcon1Click(), it can only be used to invoke a PopupMenu. Further, if a menu is not assigned, the Tray Icon may not be shown. This might be a reason do decide to use the TrayIcon with only a menu and not depend on a calling a click handler.

Tests have been conducted on a wide range of commonly used distributions and desktop combinations prior to release of Lazarus 2.0.6. Using Lazarus versions prior to that will produce different results and changes to how future Linux distribution work with the System Tray is to be expected.



Could someone expand on this comment "The image of the icon can be altered using a HICON handle. "? As a newbie I don't really know what a HICON handle is or how to use it.

HICON is a widgetset Icon Handle. The TrayIcon component is quite old, and when I first wrote it there was no real support for the TIcon component is Lazarus, so you could use directly an icon handle instead. Now you should just go for TIcon.
--Felipe Monteiro de Carvalho 08:41, 25 July 2010 (CEST)

I have found it quite hard to generate icons that will load and display using

Should work.
--Felipe Monteiro de Carvalho 08:41, 25 July 2010 (CEST)

I found that the format of the icon in Windows XP is fussy. The icon will only display if it is saved with the parameters "8bpp,1-bit alpha,256-slot palette" in gimp for example.

Ummm ... that's probably something related to the Free Pascal Windows Icon reading capabilities. 24-bits RGB should work too. Doesn't it work? You can create a test project and attach it to a bug report in the bug tracker. It would also be great if you could find out which formats work and which don't and write this in the wiki.
--Felipe Monteiro de Carvalho 08:41, 25 July 2010 (CEST)

The next challenge is to modify an icon in memory and then display it. I'm sure my method isn't exactly correct but maybe it will help others. First I tried to create a tbitmap and load an icon into it but fails. Also any attempt to do a SysTrayIcon.Icon.LoadFromBitMapHandles() seems to result in a blank icon.

In the end I did this which works for a 32x32 icon

//PByte now points to the first byte of the first pixel.
//Set the top left pixel red
Pbyte^:=$00; //green
(PByte+1)^:=$FF;  //red
(PByte+2)^:=$00:  //blue

Now I have an icon in my system tray with a red dot in the top left corner. Each pixel uses 3 bytes so a procedure like this works to manipulate each 32x32 pixel

procedure TForm1.SetIconPixel(PTRIcon:PIcon;xpos,ypos,red,green,blue:byte);
  PByte: ^Byte;
  {xpos and ypos are 0 to 31}
  if PByte<PtrIcon^.RawImage.Data+PtrIcon^.RawImage.DataSize-1 then

I have no idea what the first 100 bytes do.

For a 16x16 icon there is no extra 100 bytes and the colour order is different. Same code for a 16x16 icon

procedure TForm1.SetIconPixel(PTRIcon:PIcon;xpos,ypos,red,green,blue:byte);
  PByte: ^Byte;
  {xpos and ypos are 0 to 15}
  if PByte<PtrIcon^.RawImage.Data+PtrIcon^.RawImage.DataSize-1 then

To use this procedure you have to load an icon file or resource into a ticon send a pointer to the ticon and the xpos, ypos and colour that you want to the procedure copy the icon to the systrayicon show it

like this

//draw a black square in the middle
for x:=6 to 9 do
  for y:=6 to 9 do


Now about setting an icon pixel, there is a much better way of doing this. The RawImage is completely dependent on the pixel format you are using, but you can also use TLazIntfImage, which is format independent and very fast:
 uses Graphics, IntfGraphics;

   TempIntfImg: TLazIntfImage;
   ImgHandle,ImgMaskHandle: HBitmap;
   px, py: Integer;
   TempBitmap: TBitmap;

   // Here you can set the pixels
   for py:=0 to TempIntfImg.Height-1 do
     for px:=0 to TempIntfImg.Width-1 do
       SrcIntfImg.Colors[px,py] := clRed;

   // Now you can copy it to a TBitmap

   // And copy the TBitmap to your Icon

That should do it and very 100% format independent.
--Felipe Monteiro de Carvalho 08:40, 25 July 2010 (CEST)

I can't get TempIntfImg.CreateBitmaps(ImgHandle,ImgMaskHandle,false) to actually run getting FPImageException: Failed to create handles bug 0017031 created dieselnutjob

For reference, I added a working code here: TrayIcon#Example_2_-_Creating_the_icon_with_TLazIntfImage
--Felipe Monteiro de Carvalho 17:38, 26 July 2010 (CEST)

Your code works well. I tried it in Linux and Windows XP. just removed the unnecessary "FPRed: TFPColor;" variable thanks dieselnutjob

I am getting a new problem now. With the example code on Linux the red box is scrambled. for an example see This is laptop running Debian Lenny with KDE desktop. Lazarus is beta Date 2009-10-27 FPC 2.2.4 thanks dieselnutjob