Cocoa: Getting the "top/left" logical point of multiple screens

2
votes

I have 3 External screens on my MBP Retina 15" - Using Preferences/Displays to "arrange" the monitors in a way that mimics how they're arranged in real life.

My monitor setting

I have a small mouse position printing utility I got off of the app store. as the mouse travels, it prints the logical location of it-- and it seems to be compatible with the display arrangement.

My task is to write a program that'll enumerate them, and output the logical (top/left) coordinates of each monitor. so that those match the output of that mouse position printing utility when it's at the top/left corner. (that utility already flips the Y-coordinate) so my primary display monitor is 0,0 on the top/left corner.

I am using NSScreen's frame quite successfully, but no matter what I do, i cannot convert the Y axis output (origin.y) to top to bottom instead of cocoa's bottom to top.

How do I flip the frame NSRect on each screen such that the display arrangement is still respected?

1
macoscocoa

1 Answers

6
votes

To get the screen frames in Quartz coordinates, you can use the Quartz Display Services API:

for(NSScreen* screen in [NSScreen screens])
{
    NSRect cocoaScreenFrame = [screen frame];
    CGDirectDisplayID displayID = [[screen deviceDescription][@"NSScreenNumber"] unsignedIntValue];
    CGRect quartzScreenFrame = CGDisplayBounds(displayID);
    NSLog(@"Screen frame in Cocoa coordinate space: %@", NSStringFromRect(cocoaScreenFrame));
    NSLog(@"Screen frame in Quartz coordinate space:%@", NSStringFromRect(quartzScreenFrame));
}

If you need to convert arbitrary points or rects (e.g. mouse locations or window frames) to that coordinate space, you can take a look at this answer: In Objective-C (OS X), is the "global display" coordinate space used by Quartz Display Services the same as Cocoa's "screen" coordinate space?