I’ve released KDocker 4.4 today. It is mostly bug fixes and clean up. However, there is one major change. The feature to dock when the window decorator close button (the x in the upper corner) is clicked has been removed. This feature was introduced in 4.3 and I really like how it. It gives KDocker a feature that no similar application has. However, I was not able to keep it due to a number of issues it introduced.

The dock when closed feature was implemented via XEmbed. Basically I was creating my own window mimicking the window border of the application’s window. I would then remove the border from the application’s window and embed it into my window. Events would be passed from my window into the embedded window. This should work just fine in theory but it didn’t work out so nicely. Embedding caused five issues. The first four are serious and the last is only an annoyance.

The most serious issue was, it broke drag and drop. This looks to be an issue with X itself because I could recreate the problem using Qt and GTK’s embed support as well as writing the embed calls myself using xlib.

Another issue it caused related to support windows. When the main window was embedded it broke the connection between the main window and it’s support windows. So when docking the main window there were issues docking the applications other windows. This is an issue for applications such as XMMS and the Gimp.

Embedding didn’t get along very well with borderless windows. Applications like Chrome and XMMS draw their own window border in place of using the window manager’s decorations. These applications have special handling for moving when clicking and dragging their border. When they are embedded you end up with one of two situations. You can click and drag the window but only in the container window. So instead of moving the window you just move the window’s contents. The other situation is moving via the border doesn’t work at all. In this case resizing doesn’t work either. Oh, and the minimize, maximize, close buttons might not work either. In both cases you can still move the window using alt+left mouse button but this isn’t ideal.

Focus handling with embedded windows didn’t work correctly between different window managers and possibly different versions of Xorg. Some combinations it was fine. Others focus handling only followed the mouse. There were issues with the embedded window never getting focus or only getting focus when using alt+tab to select the window after it was docked.

The only annoying issue that I was okay with having was when undocking a window the window manager (compiz) would cause it to move a little bit. When undocking the position of the container window is recorded, the embedded window is removed from the container and moved to it’s location. Then the container window is destroyed. Compiz didn’t like placing two windows in the exact same place and kept moving the second window down and right by the size of the decoration and frame. This isn’t a very big issue but I really don’t want to have window manager specific work arounds in the code base.

The decision to remove iconify on close wasn’t taken lightly. It was only due to the large number of issues it created. There is not point in using KDocker if it is only going to make docked applications unusable. I have created a branch for iconify on close so I can hopefully get it working properly.