[gtk/gtk-3-24: 1/2] macos: correctly handle retina cursors

[John Ralls <jralls src gnome org>]

commit 021cdf382d6f12adcfc2ed1259fda8245c120347
Author: Lukas Oberhuber <lukaso gmail com>
Date:   Fri Jan 14 00:01:38 2022 +0000

    macos: correctly handle retina cursors
    
    This change correctly sizes HiDPI curors on macOS.
    
    Before this, the cursors would appear double the size of normal cursors
    on non HiDPI screens.
    Based in part on this comment:
    https://gitlab.gnome.org/GNOME/gtk/-/issues/613#note_687914

 gdk/quartz/gdkcursor-quartz.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
---
diff --git a/gdk/quartz/gdkcursor-quartz.c b/gdk/quartz/gdkcursor-quartz.c
index ad9228f90c..0a938e093d 100644
--- a/gdk/quartz/gdkcursor-quartz.c
+++ b/gdk/quartz/gdkcursor-quartz.c
@@ -261,14 +261,21 @@ _gdk_quartz_display_get_cursor_for_surface (GdkDisplay      *display,
   NSCursor *nscursor;
   GdkCursor *cursor;
   GdkPixbuf *pixbuf;
+  double x_scale;
+  double y_scale;
 
   GDK_QUARTZ_ALLOC_POOL;
 
   pixbuf = gdk_pixbuf_get_from_surface (surface, 0, 0,
                                        cairo_image_surface_get_width (surface),
                                        cairo_image_surface_get_height (surface));
+  cairo_surface_get_device_scale (surface,
+                                  &x_scale,
+                                  &y_scale);
   image = gdk_quartz_pixbuf_to_ns_image_libgtk_only (pixbuf);
-  nscursor = [[NSCursor alloc] initWithImage:image hotSpot:NSMakePoint(x, y)];
+  NSImageRep *rep = [[image representations] objectAtIndex:0];
+  [image setSize:NSMakeSize(rep.pixelsWide / x_scale, rep.pixelsHigh / y_scale)];
+  nscursor = [[NSCursor alloc] initWithImage:image hotSpot:NSMakePoint(x / x_scale, y / y_scale)];
 
   cursor = gdk_quartz_cursor_new_from_nscursor (nscursor, GDK_CURSOR_IS_PIXMAP);