Added initial implementation for Cocoa.

src/cocoa_clipboard.m

@@ -43,6 +43,12 @@
 
 void _glfwPlatformSetClipboardString(_GLFWwindow* window, const char* string)
 {
+    NSArray* types = [NSArray arrayWithObjects:NSStringPboardType, nil];
+
+    NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
+    [pasteboard declareTypes:types owner:nil];
+    [pasteboard setString:[NSString stringWithUTF8String:string]
+                  forType:NSStringPboardType];
 }
 
 
@@ -52,6 +58,30 @@ void _glfwPlatformSetClipboardString(_GLFWwindow* window, const char* string)
 
 size_t _glfwPlatformGetClipboardString(_GLFWwindow* window, char* string, size_t size)
 {
+    const char* source;
+    size_t targetSize;
+    NSPasteboard* pasteboard = [NSPasteboard generalPasteboard];
+
+    if (![[pasteboard types] containsObject:NSStringPboardType])
+    {
+        _glfwSetError(GLFW_FORMAT_UNAVAILABLE, NULL);
+        return 0;
+    }
+
+    NSString* object = [pasteboard stringForType:NSStringPboardType];
+    if (!object)
+    {
+        _glfwSetError(GLFW_PLATFORM_ERROR,
+                      "Cocoa/NSGL: Failed to retrieve object from pasteboard");
+        return 0;
+    }
+
+    source = [object UTF8String];
+    targetSize = strlen(source) + 1;
+    if (targetSize > size)
+        targetSize = size;
+
+    strlcpy(string, source, targetSize);
     return 0;
 }