Cocoa: Fix glfwSetWindowSize anchor point

This makes glfwSetWindowSize use the top-left corner as anchor point
instead of the bottom-left corner.

Fixes #1553.

README.md

@@ -128,6 +128,7 @@ information on what to include when reporting a bug.
    event (#1490)
  - [Win32] Bugfix: The window hint `GLFW_MAXIMIZED` did not move or resize the
    window (#1499)
+ - [Cocoa] Bugfix: `glfwSetWindowSize` used a bottom-left anchor point (#1553)
  - [X11] Bugfix: The CMake files did not check for the XInput headers (#1480)
  - [X11] Bugfix: Key names were not updated when the keyboard layout changed
    (#1462,#1528)
@@ -228,6 +229,7 @@ skills.
  - Peter Knut
  - Christoph Kubisch
  - Yuri Kunde Schlesner
+ - Rokas Kupstys
  - Konstantin Käfer
  - Eric Larson
  - Robin Leffmann

src/cocoa_window.m

@@ -1032,7 +1032,14 @@ void _glfwPlatformSetWindowSize(_GLFWwindow* window, int width, int height)
             acquireMonitor(window);
     }
     else
-        [window->ns.object setContentSize:NSMakeSize(width, height)];
+    {
+        NSRect contentRect =
+            [window->ns.object contentRectForFrameRect:[window->ns.object frame]];
+        contentRect.origin.y += contentRect.size.height - height;
+        contentRect.size = NSMakeSize(width, height);
+        [window->ns.object setFrame:[window->ns.object frameRectForContentRect:contentRect]
+                            display:YES];
+    }
 
     } // autoreleasepool
 }