In a prior commit (38e00280e9d17282717595a05411736a308804c0), I added support to stick applets to the center of the panel, so that no matter the width of the applet or the panel, the applet would always stay at the center of the panel. That commit also added an "end-relative" mode, which is similar to the panel's old "right-stick" feature, except end-relative mode positions the applet's right edge relative to the panel's right edge, whereas right-sticking positioned the applet's left edge relative to the right edge of the panel. The advantage of end-relative positioning is that the applet can resize without moving itself even further to the right than the user intended, whereas if positioned so that there is empty space between the applet and the edge of the panel, right-stuck applets would change the size of that gap (or close it entirely) when the applet resized. Unfortunately, I have since discovered that my original implementation of the center-stick and end-relative positioning of applets was inadequate. Some applets can accept any amount of space between a minimum and their "preferred" size -- if such an applet cannot be allocated its preferred size (perhaps because panel space is scarce), then the applet will be allocated as much space as is available, and the applet will "flex" itself to compensate. Some examples of these "expanding" applets include the Window List (a component of the wncklet included in this package) and the MATE Dock Applet (a third-party panel applet from the Ubuntu MATE project). When writing my original center-stick code, I did not properly take expanding applets into account, and with my original commit, such applets were off-center -- usually way off-center since the code seemed to position such applets based on their minimum size, rather than their actual allocated size. This commit adds center-sticking support for expanding applets. It also works with end-relative expanding applets -- such applets will expand towards the left, thus keeping their right-relative position intact.