Avoid using timing related hacks to detect the end of a live resize on macOS

Since cocoa provides start/end notifications for live resizing, rely on
those instead.

glfw/cocoa_window.m

@@ -592,6 +592,17 @@ static GLFWapplicationshouldhandlereopenfun handle_reopen_callback = NULL;
     return YES;
 }
 
+- (void) viewWillStartLiveResize
+{
+    _glfwInputLiveResize(window, true);
+}
+
+- (void)viewDidEndLiveResize
+{
+    _glfwInputLiveResize(window, false);
+}
+
+
 - (BOOL)wantsUpdateLayer
 {
     return YES;

glfw/glfw3.h

@@ -1474,6 +1474,8 @@ typedef void (* GLFWkeyboardfun)(GLFWwindow*, int, int, int, int, const char*, i
  */
 typedef void (* GLFWdropfun)(GLFWwindow*,int,const char**);
 
+typedef void (* GLFWliveresizefun)(GLFWwindow*, bool);
+
 /*! @brief The function signature for monitor configuration callbacks.
  *
  *  This is the function signature for monitor configuration callback functions.
@@ -4343,6 +4345,7 @@ GLFWAPI GLFWscrollfun glfwSetScrollCallback(GLFWwindow* window, GLFWscrollfun cb
  *  @ingroup input
  */
 GLFWAPI GLFWdropfun glfwSetDropCallback(GLFWwindow* window, GLFWdropfun cbfun);
+GLFWAPI GLFWliveresizefun glfwSetLiveResizeCallback(GLFWwindow* window, GLFWliveresizefun cbfun);
 
 /*! @brief Returns whether the specified joystick is present.
  *

glfw/internal.h

@@ -419,6 +419,7 @@ struct _GLFWwindow
         GLFWscrollfun           scroll;
         GLFWkeyboardfun         keyboard;
         GLFWdropfun             drop;
+        GLFWliveresizefun       liveResize;
     } callbacks;
 
     // This is defined in the window API's platform.h
@@ -653,6 +654,7 @@ void _glfwPlatformSetWindowSizeLimits(_GLFWwindow* window,
                                       int maxwidth, int maxheight);
 void _glfwPlatformSetWindowAspectRatio(_GLFWwindow* window, int numer, int denom);
 void _glfwPlatformGetFramebufferSize(_GLFWwindow* window, int* width, int* height);
+void _glfwInputLiveResize(_GLFWwindow* window, bool started);
 void _glfwPlatformGetWindowFrameSize(_GLFWwindow* window,
                                      int* left, int* top,
                                      int* right, int* bottom);

glfw/window.c

@@ -139,6 +139,14 @@ void _glfwInputFramebufferSize(_GLFWwindow* window, int width, int height)
         window->callbacks.fbsize((GLFWwindow*) window, width, height);
 }
 
+// Notifies shared code that a window live resize is in progress
+//
+void _glfwInputLiveResize(_GLFWwindow* window, bool started)
+{
+    if (window->callbacks.liveResize)
+        window->callbacks.liveResize((GLFWwindow*) window, started);
+}
+
 // Notifies shared code that a window content scale has changed
 // The scale is specified as the ratio between the current and default DPI
 //
@@ -1122,6 +1130,17 @@ GLFWAPI GLFWframebuffersizefun glfwSetFramebufferSizeCallback(GLFWwindow* handle
     return cbfun;
 }
 
+GLFWAPI GLFWliveresizefun glfwSetLiveResizeCallback(GLFWwindow* handle,
+                                                              GLFWliveresizefun cbfun)
+{
+    _GLFWwindow* window = (_GLFWwindow*) handle;
+    assert(window != NULL);
+
+    _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
+    _GLFW_SWAP_POINTERS(window->callbacks.liveResize, cbfun);
+    return cbfun;
+}
+
 GLFWAPI GLFWwindowcontentscalefun glfwSetWindowContentScaleCallback(GLFWwindow* handle,
                                                                     GLFWwindowcontentscalefun cbfun)
 {