Cocoa: Replace display link with IOKit query

This removes the final dependency on CoreVideo, using a display link to
get the refresh rate of monitors where Core Graphics report a refresh
rate of zero.  Instead we now query the I/O registry directly, similarly
to what the display link does at creation.

Thanks to @OneSadCookie for pointers to this solution.

CMakeLists.txt

@@ -275,11 +275,10 @@ if (_GLFW_COCOA)
     list(APPEND glfw_LIBRARIES
         "-framework Cocoa"
         "-framework IOKit"
-        "-framework CoreFoundation"
-        "-framework CoreVideo")
+        "-framework CoreFoundation")
 
     set(glfw_PKG_DEPS "")
-    set(glfw_PKG_LIBS "-framework Cocoa -framework IOKit -framework CoreFoundation -framework CoreVideo")
+    set(glfw_PKG_LIBS "-framework Cocoa -framework IOKit -framework CoreFoundation")
 endif()
 
 #--------------------------------------------------------------------

README.md

@@ -139,6 +139,7 @@ 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] Removed dependency on the CoreVideo framework
  - [Cocoa] Bugfix: `glfwSetWindowSize` used a bottom-left anchor point (#1553)
  - [Cocoa] Bugfix: Window remained on screen after destruction until event poll
    (#1412)

docs/build.dox

@@ -344,8 +344,8 @@ If you are using the dynamic library version of GLFW, add it to the project
 dependencies.
 
 If you are using the static library version of GLFW, add it and the Cocoa,
-OpenGL, IOKit and CoreVideo frameworks to the project as dependencies.  They can
-all be found in `/System/Library/Frameworks`.
+OpenGL and IOKit frameworks to the project as dependencies.  They can all be
+found in `/System/Library/Frameworks`.
 
 
 @subsection build_link_osx With command-line on macOS
@@ -359,7 +359,7 @@ the `-l` and `-framework` switches.
 If you are using the dynamic GLFW library, which is named `libglfw.3.dylib`, do:
 
 @code{.sh}
-cc -o myprog myprog.c -lglfw -framework Cocoa -framework OpenGL -framework IOKit -framework CoreVideo
+cc -o myprog myprog.c -lglfw -framework Cocoa -framework OpenGL -framework IOKit
 @endcode
 
 If you are using the static library, named `libglfw3.a`, substitute `-lglfw3`

docs/news.dox

@@ -52,6 +52,12 @@ add_subdirectory(path/to/glfw)
 @endcode
 
 
+@subsubsection corevideo_34 CoreVideo dependency has been removed
+
+GLFW no longer depends on the CoreVideo framework on macOS and it no longer
+needs to be specified during compilation or linking.
+
+
 @subsection deprecations_34 Deprecations in version 3.4
 
 @subsection removals_34 Removals in 3.4

src/cocoa_monitor.m

@@ -234,26 +234,65 @@ static GLFWbool refreshMonitorScreen(_GLFWmonitor* monitor)
     return GLFW_FALSE;
 }
 
-// Returns a fallback refresh rate for when Core Graphics says it is zero
+// Returns the display refresh rate queried from the I/O registry
 //
-static double getFallbackRefreshRate(_GLFWmonitor* monitor)
+static double getFallbackRefreshRate(CGDirectDisplayID displayID)
 {
-    CGDisplayModeRef mode = CGDisplayCopyDisplayMode(monitor->ns.displayID);
-    double refreshRate = CGDisplayModeGetRefreshRate(mode);
-    CGDisplayModeRelease(mode);
+    double refreshRate = 60.0;
 
-    if (refreshRate == 0.0)
+    io_iterator_t it;
+    io_service_t service;
+
+    if (IOServiceGetMatchingServices(kIOMasterPortDefault,
+                                     IOServiceMatching("IOFramebuffer"),
+                                     &it) != 0)
     {
-        CVDisplayLinkRef link = NULL;
-        CVDisplayLinkCreateWithCGDisplay(monitor->ns.displayID, &link);
-
-        const CVTime time = CVDisplayLinkGetNominalOutputVideoRefreshPeriod(link);
-        if (!(time.flags & kCVTimeIsIndefinite))
-            refreshRate = (int) (time.timeScale / (double) time.timeValue);
-
-        CVDisplayLinkRelease(link);
+        return refreshRate;
     }
 
+    while ((service = IOIteratorNext(it)) != 0)
+    {
+        const CFNumberRef indexRef =
+            IORegistryEntryCreateCFProperty(service,
+                                            CFSTR("IOFramebufferOpenGLIndex"),
+                                            kCFAllocatorDefault,
+                                            kNilOptions);
+        if (!indexRef)
+            continue;
+
+        uint32_t index = 0;
+        CFNumberGetValue(indexRef, kCFNumberIntType, &index);
+        CFRelease(indexRef);
+
+        if (CGOpenGLDisplayMaskToDisplayID(1 << index) != displayID)
+            continue;
+
+        const CFNumberRef clockRef =
+            IORegistryEntryCreateCFProperty(service,
+                                            CFSTR("IOFBCurrentPixelClock"),
+                                            kCFAllocatorDefault,
+                                            kNilOptions);
+        const CFNumberRef countRef =
+            IORegistryEntryCreateCFProperty(service,
+                                            CFSTR("IOFBCurrentPixelCount"),
+                                            kCFAllocatorDefault,
+                                            kNilOptions);
+        if (!clockRef || !countRef)
+            break;
+
+        uint32_t clock = 0, count = 0;
+        CFNumberGetValue(clockRef, kCFNumberIntType, &clock);
+        CFNumberGetValue(countRef, kCFNumberIntType, &count);
+        CFRelease(clockRef);
+        CFRelease(countRef);
+
+        if (clock > 0 && count > 0)
+            refreshRate = clock / (double) count;
+
+        break;
+    }
+
+    IOObjectRelease(it);
     return refreshRate;
 }
 
@@ -310,10 +349,14 @@ void _glfwPollMonitorsNS(void)
         _GLFWmonitor* monitor = _glfwAllocMonitor(name, size.width, size.height);
         monitor->ns.displayID  = displays[i];
         monitor->ns.unitNumber = unitNumber;
-        monitor->ns.fallbackRefreshRate = getFallbackRefreshRate(monitor);
 
         free(name);
 
+        CGDisplayModeRef mode = CGDisplayCopyDisplayMode(displays[i]);
+        if (CGDisplayModeGetRefreshRate(mode) == 0.0)
+            monitor->ns.fallbackRefreshRate = getFallbackRefreshRate(displays[i]);
+        CGDisplayModeRelease(mode);
+
         _glfwInputMonitor(monitor, GLFW_CONNECTED, _GLFW_INSERT_LAST);
     }
 

src/cocoa_platform.h

@@ -28,8 +28,6 @@
 #include <dlfcn.h>
 
 #include <Carbon/Carbon.h>
-#include <CoreVideo/CVBase.h>
-#include <CoreVideo/CVDisplayLink.h>
 
 // NOTE: All of NSGL was deprecated in the 10.14 SDK
 //       This disables the pointless warnings for every symbol we use