When using the Changes -> Diff window on a Linux system with two monitors configured as a single desktop (using nVidia TwinView) it is not possible to make the window any wider than one of the monitors plus about 10 pixels. For example, I have two monitors configured as one desktop, each monitor resolution is 1280 pixels wide, so my total desktop width is 2560 pixels. When resizing other windows (for example the main IDEA window) there is no problem to resize them to use the entire width of the desktop, i.e. 2560 pixels, but the Diff window refuses to be made any wider than about 1290 pixels or so. It appears it is not possible to make it taller than one monitor either, although this doesn't concern me. The Diff3 window (for merge conflicts) works fine, as does every other child window we have tried. The problem does not occur on Windows with two monitors.