I use both "Open" (Cmd+O) and "Open Quickly" (Cmd+Shift+D) in XCode to display source files in my project without having to navigate the source tree with the mouse.
Most files are opened in a new source window, but for some files, XCode insists on simply bringing up the multi-pane project window and displaying the specified source file inside the source display pane.
The arbitrariness of this is driving me insane. Can anyone fill me in on why XCode deems certain files worthy of their own window, and others not? Is there a way I can make this behavior consistent?