static int letUserMarkScreenArea_shootAfterClickDelay = 1000;

static void letUserMarkScreenArea(final O f) {
  letUserMarkScreenArea(shootScreen2(), f);
}

// f: voidfunc(Rectangle r, BufferedImage screenshot) - gets called with null values on abort
static void letUserMarkScreenArea(final BufferedImage screenshot, final O f) {
  final JWindow window = showAnimationInTopRightCorner("#1005611", "Please click roughly in the area you would like to select");

  trackOneClick(voidfunc(final Point p) {
    final new Flag done;
    window.dispose();
    
    thread "Shooting Screen" {
      sleep(screenshot == null ? letUserMarkScreenArea_shootAfterClickDelay : 0);
      awt {
        final BufferedImage screenshot2 = screenshot == null ? shootScreen2() : screenshot;
  
        final ImageSurface is = imageSurface(screenshot2);
        is.setZoom(4);
        JFrame frame = showCenterFrame("Please select exact area and click OK", jScrollPane(is));
        setFrameBounds(frame, centerScreenPart(0.75));
        addToWindow(frame, withInset(imageSelectionDepend(is, jbutton("OK", r {
          Rectangle r = is.selection;
          if (r != null) {
            disposeWindow(is);
            done.raise();
            callF(f, r, screenshot2);
          }
        }))));
        is.centerPoint(p);
        onFrameClose(frame, r {
          if (!done.isUp()) {
            done.raise();
            callF(f, null, null);
          }
        });
      }
    }
  });
}

Began life as a copy of #1005662