How to create a taskbar icon using wxPHP in Ubuntu / Unity?

Question

After some struggle, I compiled a PHP module for wxPHP and wrote some scripts to see what it can do. My first demo creates a window and a taskbar icon, and I can't get the latter to work.

I am running this on Ubuntu 14.04 LTS.

Here is the script I am using:

<?php // Create an icon (does not appear on Ubuntu 14.04 LTS) $icon = new wxTaskBarIcon(); echo "Task bar available: " . (wxTaskBarIcon::IsAvailable() ? 'Yes' : 'No') . "\n"; echo "Create task bar icon: " . ($icon ? 'OK' : 'Failed') . "\n"; $wxIcon = new wxIcon('icon.ico'); $ok = $icon->setIcon($wxIcon); echo "Set image for icon: " . ($ok ? 'OK' : 'Failed') . "\n"; // Create a window (works fine) $main = new wxFrame(null, wxID_TOP, "Title" ); $main->Show(); wxEntry(); 

Now I would suggest that the "taskbar" in Unity is the top panel with the clock, sound and network controls, and not the application panel on the left. I get a blank gray app icon in the dock when the PHP task is running, but this is the status icon at the top, which I follow.

The console outputs from the above script show that everything is in order:

 Task bar available: Yes Create task bar icon: OK Set image for icon: OK 

I tried changing icon.ico to a nonexistent file, and this brings up the backtrace dialog, which shows that the icon I'm using is loading successfully (and presumably from an acceptable format).

Edit: Further studies show that:

• earlier versions of Ubuntu prevented applications from using the panel if it is not listed separately in the white list (note that the gsettings keys specified here gsettings not found in my later version of Ubuntu)
• later versions require something called AppIndicators

Thus, I am assuming that my code would work if it weren't for Unity preventing the operation, and that it would be immediately on other distributions such as Mint.

I found this guide that explains how to use the whitelist on Ubuntu 14, but this is most unsatisfactory; to do something so trivial, you don’t have to change the list of trusted repos. If I want to distribute an application written in wxPHP, users will (and should) find it unacceptable.

There are several research opportunities that I now ask for advice:

• Do something different in wxPHP if it (or up wxWidgets) supports AppIndicators (I think it is not)
• Detecting if AppIndicators is running, and if it sends DBus messages using PHP to create an icon (although I looked for a DBus message specification for AppIndicators in vain)

Edit again: since this is a pretty niche question, and since Ask Ubuntu contains a number of programming questions for the Ubuntu platform, I asked a question specific to DBus on this site.

Answer 1

In general, it is not possible to create a taskbar icon on Ubuntu, at least through wxPHP or wxWidgets. This is a deliberate design decision from the Ubuntu usability team to represent consistency and accessibility in the use of application-level status icons.

I raised this as an error and received a lot of useful information from the accompanying wxPHP. I agree with him that this feature will be better upstream in wxWidgets, but from the comments on the Internet it doesn't seem like there is a lot of appetite to add it there.

My short-term solution would be to configure the Python process to use its own App indicator ( python-appindicator in the Ubuntu repo) and establish a connection between the two processes (from PHP to Python to change the icon, from Python to PHP to send menu selection events). I expect to start by using wxFileSystemWatcher as a simple communication system, as it works well inside the wxWidgets event loop.

A better solution would be to have appindicator bindings for PHP, but that sounds more active, so I will leave it for now.