From 842aeb8c470eb93459cd152354522cd7269033c1 Mon Sep 17 00:00:00 2001
From: Camilla Berglund <elmindreda@elmindreda.org>
Date: Sun, 20 Sep 2015 16:25:00 +0200
Subject: [PATCH] Make Win32 video mode enumeration faster

---
 src/win32_monitor.c  | 25 ++++++++++++++++---------
 src/win32_platform.h |  1 +
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/win32_monitor.c b/src/win32_monitor.c
index be5686f8..5b235db6 100644
--- a/src/win32_monitor.c
+++ b/src/win32_monitor.c
@@ -152,6 +152,9 @@ _GLFWmonitor** _glfwPlatformGetMonitors(int* count)
             DeleteDC(dc);
             free(name);
 
+            if (adapter.StateFlags & DISPLAY_DEVICE_MODESPRUNED)
+                monitor->win32.modesPruned = GL_TRUE;
+
             wcscpy(monitor->win32.adapterName, adapter.DeviceName);
             wcscpy(monitor->win32.displayName, display.DeviceName);
 
@@ -226,15 +229,6 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* count)
 
         modeIndex++;
 
-        if (ChangeDisplaySettingsExW(monitor->win32.adapterName,
-                                    &dm,
-                                    NULL,
-                                    CDS_TEST,
-                                    NULL) != DISP_CHANGE_SUCCESSFUL)
-        {
-            continue;
-        }
-
         // Skip modes with less than 15 BPP
         if (dm.dmBitsPerPel < 15)
             continue;
@@ -257,6 +251,19 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* count)
         if (i < *count)
             continue;
 
+        if (monitor->win32.modesPruned)
+        {
+            // Skip modes not supported by the connected displays
+            if (ChangeDisplaySettingsExW(monitor->win32.adapterName,
+                                         &dm,
+                                         NULL,
+                                         CDS_TEST,
+                                         NULL) != DISP_CHANGE_SUCCESSFUL)
+            {
+                continue;
+            }
+        }
+
         if (*count == size)
         {
             if (*count)
diff --git a/src/win32_platform.h b/src/win32_platform.h
index e8e32dfc..d3e190e9 100644
--- a/src/win32_platform.h
+++ b/src/win32_platform.h
@@ -203,6 +203,7 @@ typedef struct _GLFWmonitorWin32
     WCHAR               displayName[32];
     char                publicAdapterName[64];
     char                publicDisplayName[64];
+    GLboolean           modesPruned;
     GLboolean           modeChanged;
 
 } _GLFWmonitorWin32;