Here’s a little command that’s just vital for efficient use of apps like Gimp and Inkscape on the Mac:
defaults write com.apple.x11 wm_click_through -bool true
By default quartz-wm swallows the first click on a window, the one that gives the window focus. Real Mac apps can control that behavior, but obviously X11 apps can’t, even when they are toolbar windows that really, really need to accept the first click in order not to be terribly frustrating to use.
I can’t believe I actually went two years before breaking down and looking up how to do this.