Created attachment 5369 
Remember the window size of the settings dialog

Currently, the settings window does not remember its size, and one always has to resize it after opening it. If resolution allows it, it is much better to have a bigger window so one can see more images, but its a bit annoying having it to resize it every time. I've copied and adapted the code to remember the size from xfce4-settings. Patch attached and applies to current git.