How to use a TrayIcon
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TrayIcon used to be an optional component, but is part of LCL since Lazarus 0.9.23
To start quickly, please read the demonstration program.
Linux may not display the Icon
Some Linux systems will have trouble displaying the GTK TrayIcon, in general this relates to a move away from the System Tray model that Lazarus TrayIcon is based on. This problem is a particular issue with Gnome but some other Desktops may also suffer. There are workarounds that involve using another library, and in some cases other extra packages and specific configuration steps. Its important to note, and to advise your end users, that the problem is with the Linux Distribution and its Desktop. You, as the application's programmer cannot directly solve the problem. Sadly, your app cannot tell if the TrayIcon is visible or not on an uncooperative Desktops !
At the time of writing, October 2019, Gnome desktop versions of Fedora, Red Hat, Suse and Mageia and Debian all require a AppIndicator library be installed and the Gnome Shell Extension, gnome-shell-extension-appindicator be installed and enabled, see below.
Mageia Enlightenment also requires an AppIndicator library and enabling System Tray in Settings->Modules and the adding that System Tray to a Shelf (all terms familiar to Enlightenment users). Unfortunately, even that gets 'an' icon, not the one you carefully select for your application.
As of Lazarus 2.0.6, LCL will attempt to 'guess' the correct model to display a Tray Icon. However as distributions change over time, or with more obscure distributions you may need to override these guesses. For GTK2 apps, by setting an environment variable, LAZUSEAPPIND you can force an app to try to use LibAppIndicator3, prevent it from trying or just tell us which way it has guessed using YES, NO or INFO. eg
LAZUSEAPPIND=YES project1 <enter>
Will force project1 to try to use an Appindicator library (instead of the traditional System Tray) on GTK2. Obviously, it may not be available or it may not be suitable for the desktop in use but it will try. A line or two of text will be printed on stdout if the var is defined and not blank. Many systems will display the TrayIcon without using this environment variable. If the desktop you are running does require an AppIndicator library, then you must accept all it can ever do is trigger a menu, no OnClick event.
GTK3 can support only the AppIndicator model. Its use of the Ayatana version (in trunk only) is determined by https://bugs.freepascal.org/view.php?id=38909
Why two models ?
The AppIndicator model does not do as much as the older System Tray model. Both libraries are derived from Unity's definition of a 'simpler' interface, it will display only a menu, it does not pass an event, OnClick, back to your app. Indeed, if you have not assigned a popup menu to your TrayIcon will not show up at all. So, applications that depend on getting a OnClick event will not work with LibAppIndicator3.
Developers of new applications may well be advised to design their program around TrayIcon using only a popUpMenu !
There are currently two possible AppIndicator libraries, Canonical's LibAppIndicator3-1 or libayatana-appindicator3-1, some systems have both, Bullseye has only the Ayatana one. Lazarus trunk supports Ayatana after 22 May 2021, r65122 and in 2.2.0. See External Links, below about the shift to Ayatana.
One or the other library can generally be installed from your distribution's normal package library. However, it is packaged with a number of different names. Sigh ...
- libappindicator3 - Slackware, NetBSD
- libappindicator3-1 - openSUSE and Debian [-based]
- libappindicator-gtk3 - Arch, ALT, CentOS and Fedora, RedHat
- libappindicator3_1 - all Mandrake/Mandriva derivatives -- Mageia, OpenMandriva, PCLinuxOS, Rosa
- libayatana-appindicator3-1 - Debian Bullseye and most other Linuxs that offer Ayatana.
This seems to be a viable solution mid 2021 for Gnome based systems. This plugin for Gnome Shell (the desktop) is made by Ubuntu to work like its old Unity AppIndicator model. So, in addition the the gnome plugin, you also need to install an AppIndicator3 library (AppIndicator3-1 on Fedora, Ayanata on Bullseye). It is KNSI inspired so no fancy right clicks allowed, just assign it a menu.
On Fedora, you can do this (note you don't need gnome-tweaks on Fedora 34) -
sudo dnf install libappindicator-gtk3 gnome-shell-extension-appindicator gnome-tweaks [enter]
Once installed, you need to restart the Desktop, just logout and back in. Then you must 'enable' the new plugin. On Fedora 33 thats easy, use the gnome-tweaks command, Extensions, enable "Kstatusnotifieritem/appindicator support". On Fedora 34, they have made it a bit harder by removing the Extensions section from Gnome Tweaks (too many happy users I expect). So, with Fedora 34, use the gnome-extensions command, it does not have a gui so issue the following command -
gnome-extensions enable firstname.lastname@example.org [enter]
Replace 'enable' with 'info' to get some diagnostic information.
Note, three steps, install, restart desktop, enable plugin !
Debian Bullseye appears to arrive with the Ayatana library pre installed but the Gnome version still requires gnome-shell-extension-appindicator, install as above.
Your application can enable the extension (after a desktop restart), if you are feeling brave see https://github.com/tomboy-notes/tomboy-ng/blob/master/source/mainunit.pas
Sadly, the coming of Wayland seems to have killed TopIconsPlus. This section may be removed before long.
Checking before invoking TrayIcon
Because you app may show the user only its TrayIcon and if that's not visible the user cannot interact, you may like to test to see if its going to work. Firstly, you can, sort of determine if LCL will use the old System Tray (in which case it will probably be OK), look at code in lcl/interfaces/gtk2/UnityWSCtrl.pas. If LCL is going to use an AppIndicator library, you need to see if the library is available and, on a Gnome system, if gnome-shell-extension-appindicator is enabled. The library is easy, try and load it, an error says its not there. To see if TopIcons is going to be available, the command "dconf read /org/gnome/shell/enabled-extensions" returns a few strings that may include "TopIcons". I expect there may also be an API ....
Trunk from October 2019 has a working GTK3 TrayIcon based, again, on LibAppIndicator3. The advice above relation to installing LibAppindicator3 and, where necessary TopIconsPlus applies to GTK3 as well. As the only way you can get a TrayIcon under GTK3 is the LibAppIndicator3, you can only use it to display a popup menu, don't expect to get a working OnClick event.
QT5 on Linux
Some linux systems that won't display the GTK Tray Icon will display the Qt5 version, but only if they use XOrg. Any system using wayland apparently has other has issues with Qt5. Fedora and OpenSuse use wayland by default but users can choose to use XOrg instead at logon time.
Issue On the macOS 32 bit Carbon
In October 2017 it was noted that a small problem existed on Sierra 10.12 when using the Carbon widget set. Attempts to update the caption of a menu item in a popup menu associated with a TrayIcon do not happen as expected. It is not uncommon to want to update the menu text at run time, for example, to display a list of recently opened files. This problem has been logged, https://bugs.freepascal.org/view.php?id=32516 . A workaround that appears reliable is to call
TrayIcon1.InternalUpdate; after making changes to the captions.
This problem does not exist on Linux, Windows or on macOS when using the 64 bit Cocoa widget set.
Below is a list of all methods, properties and events of the component. They have the same names and work the same way on the visual component and on the non-visual object.
A function works on all target platforms unless written otherwise.
Shows the icon on the system tray.
Removes the icon from the system tray.
function GetPosition: TPoint;
Returns the position of the tray icon on the display. This function is utilized to show message boxes near the icon. Currently it´s only a stub, no implementations are available and TPoint(0, 0) is returned.
property Hint: string;
A Hint will be shown the string isn't empty
property PopUpMenu: TPopUpMenu;
A PopUp menu that appears when the user right-clicks the tray icon.
property OnPaint: TNotifyEvent;
Use this to implement custom drawing to the icon. Draw using the canvas property of the icon.
property OnClick: TNotifyEvent;
property OnDblClick: TNotifyEvent;
property OnMouseDown: TMouseEvent;
property OnMouseUp: TMouseEvent;
property OnMouseMove: TMouseMoveEvent;
Can be located at Lazarus 0.9.22 or inferior at the directory: lazarus/components/trayicon
And on Lazarus 0.9.23 or superior it is automatically installed with LCL
Example 1 - Using TIcon
As of Lazarus 0.9.26 TIcon has been fully implemented and it is no longer necessary to load the icon from a resource file on Windows. The icon can be loaded in the IDE or with usual code.
Go to the Additional tab of components, and add a TTrayIcon to your form. Then change its Name property to SystrayIcon
Next add a button to the form. Double click the button and add this code to it:
procedure MyForm.Button1Click(Sender: TObject); begin SystrayIcon.Icon.LoadFromFile('/path_to_icon/icon.ico'); SystrayIcon.ShowHint := True; SystrayIcon.Hint := 'my tool tip'; SystrayIcon.PopUpMenu := MyPopUpMenu; SystrayIcon.Show; end;
Example 2 - Creating the icon with TLazIntfImage
You can use TLazIntfImage to draw your icon quickly, as in the example code below:
procedure TForm1.DrawIcon; var TempIntfImg: TLazIntfImage; ImgHandle, ImgMaskHandle: HBitmap; px, py: Integer; TempBitmap: TBitmap; begin try TempIntfImg := TLazIntfImage.Create(16, 16); TempBitmap := TBitmap.Create; TempBitmap.Width := 16; TempBitmap.Height := 16; TempIntfImg.LoadFromBitmap(TempBitmap.Handle, TempBitmap.MaskHandle); // Set the pixels red for py := 0 to TempIntfImg.Height - 1 do for px := 0 to TempIntfImg.Width - 1 do TempIntfImg.Colors[px, py] := colRed; // Copy it to a TBitmap TempIntfImg.CreateBitmaps(ImgHandle,ImgMaskHandle, False); TempBitmap.Handle := ImgHandle; TempBitmap.MaskHandle := ImgMaskHandle; // And copy the TBitmap to your Icon SystrayIcon.Icon.Assign(TempBitmap); SystrayIcon.Show; finally TempIntfImg.Free; TempBitmap.Free; end; end;
Located under components/trayicon/ on the latest subversion Lazarus.
Help, Bug Reporting and Feature Request
Please, post Bug Reports and Feature Requests on the Lazarus Bugtracker.
Help requests can be posted on the Lazarus mailing list or on the Lazarus Forum.
- 17/01/2006 - Available as a preview on the Lazarus subversion. Still under heavy construction, however.
- 24/01/2006 - Stable under win32, gnome and gtk1, but still waiting for gtk2 support. Lazarus 0.9.12 was release with this version.
- 17/02/2006 - Added support for gtk2 on subversion.
- July 2008 - Implements support for Qt 4
- July 2008 - Implements support for Carbon through PasCocoa
A difficulty on the development of this component was the many differences on the system tray implementation on various OSes and even Window Managers on Linux. To solve this, the component tries to implement the minimal set of features common to all target platforms. Below is a list of the features implemented on each platform:
Windows - Multiple system tray icons per application are supported. The image of the icon can be altered using a HICON handle. Events to the icon are sent via a special message on the user reserved space of messages (>= WM_USER) to the Window which owns the Icon. No paint events are sent to the Window.
Linux (Gnome, KDE, IceWM, etc) - Multiple system tray icons per application are supported. The image of the icon is actually a very small Window, and can be painted and receive events just like any other TForm descendant.
macOS - TTrayIcon support is implemented using the menu bar extras. Unfortunately the API to use menu bar extras is only available in Cocoa and not in Carbon, so we use the stable PasCocoa bindings in the Carbon interface to support menu bar extras even in older FPC compilers and in the Cocoa interface we will use the more modern Objective Pascal syntax.
To read more about menu bar extras:
With this in mind an approach which supports all Platforms was created:
- Painting is done via a TIcon object. (Required by Windows)
The following extra features are already available or will be, but they won´t work on all platforms.
- OnPaint event and Canvas property to draw the icon freely. Won´t work on Windows.
- http://www.codeproject.com/shell/ctrayiconposition.asp - Code and theory to find the tray icon position under Windows
- http://cvs.gnome.org/viewcvs/gtk%2B/gtk/gtkstatusicon.c?rev=1.23&view=markup - Gtk2 code that implements gtkstatusicon
- http://pasmontray.sourceforge.net - Open source program that uses TrayIcon to display CPU and memory utilisation in the system tray.
- Background to Debian's switch from libappindicator to Ayatana