How to emulate the cmd-shift-4 screen capture interface?

Question

I am building an OSX app and would like to capture a portion of the screen with a similar interface as the cmd-shift-4 UX, IE initiating the action:

1. presents a mouse cursor
2. mouseDown and drag, mouseUp captures the screen coordinates while drawing a translucent overlay to denote the area being captured

I've found a good starting point in http://code.google.com/p/captureme/ which presents an NSPanel and captures the area within the panel. However I'd like do a bit better and emulate the cmd-shift-4 interface.

I can't find if something like this is built in (or if there's an existing solution). I suppose the straight forward way is to use an NSResponder and replace the cursor on mouseDown, then on a mouse drag event draw a translucent rectangle between the mouseDown point and the current cursor location. Let me know if my thinking is along the correct lines.

Thanks!

Answer 1

Here's the nutshell version of what you want to do: Create a fullscreen transparent window at CGShieldingWindowLevel(), setIgnoresMouseEvents:NO, have the view set the cursor to whatever you want, and implement dragging to draw the marquee in the dragged area.