The cocoa crate links to AppKit, which made the symbol `CGDisplayCr…

…eateUUIDFromDisplayID` from ApplicationServices/ColorSync (which AppKit uses internally) available to us on macOS 10.8 to 10.13. (#275)

However, this does not work on macOS 10.7 (where AppKit does not link to ColorSync internally). Instead of relying on this, we should just link to ApplicationServices directly.

.changes/mac-link.md

@@ -0,0 +1,6 @@
+---
+"tao": patch
+---
+
+Fix linking to the `ColorSync` framework on macOS 10.7, and in newer Rust versions.
+

src/platform_impl/macos/ffi.rs

@@ -168,9 +168,18 @@ pub const IO8BitOverlayPixels: &str = "O8";
 pub type CGWindowLevel = i32;
 pub type CGDisplayModeRef = *mut libc::c_void;
 
+// `CGDisplayCreateUUIDFromDisplayID` comes from the `ColorSync` framework.
+// However, that framework was only introduced "publicly" in macOS 10.13.
+//
+// Since we want to support older versions, we can't link to `ColorSync`
+// directly. Fortunately, it has always been available as a subframework of
+// `ApplicationServices`, see:
+// https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/OSX_Technology_Overview/SystemFrameworks/SystemFrameworks.html#//apple_ref/doc/uid/TP40001067-CH210-BBCFFIEG
+//
+// TODO: Remove the WINIT_LINK_COLORSYNC hack, it is probably not needed.
 #[cfg_attr(
   not(use_colorsync_cgdisplaycreateuuidfromdisplayid),
-  link(name = "CoreGraphics", kind = "framework")
+  link(name = "ApplicationServices", kind = "framework")
 )]
 #[cfg_attr(
   use_colorsync_cgdisplaycreateuuidfromdisplayid,