From cf177905e506cdd21e86896e24201230aff953d9 Mon Sep 17 00:00:00 2001
From: Camilla Berglund <elmindreda@elmindreda.org>
Date: Mon, 10 Feb 2014 15:03:23 +0100
Subject: [PATCH] Allowed drops from less privileged processes.

By default, UAC will prevent less privileged processes from sending
these messages.  This resolves that on Windows 7 and later.  Windows
Vista is still affected by this issue, as it has UAC but lacks
ChangeWindowMessageFilterEx.

Fixes #227.
---
 src/win32_init.c     |  2 ++
 src/win32_platform.h | 17 +++++++++++++++++
 src/win32_window.c   | 10 ++++++++++
 3 files changed, 29 insertions(+)

diff --git a/src/win32_init.c b/src/win32_init.c
index 94190398..cc33bc38 100644
--- a/src/win32_init.c
+++ b/src/win32_init.c
@@ -96,6 +96,8 @@ static GLboolean initLibraries(void)
     {
         _glfw.win32.user32.SetProcessDPIAware = (SETPROCESSDPIAWARE_T)
             GetProcAddress(_glfw.win32.user32.instance, "SetProcessDPIAware");
+        _glfw.win32.user32.ChangeWindowMessageFilterEx = (CHANGEWINDOWMESSAGEFILTEREX_T)
+            GetProcAddress(_glfw.win32.user32.instance, "ChangeWindowMessageFilterEx");
     }
 
     _glfw.win32.dwmapi.instance = LoadLibrary(L"dwmapi.dll");
diff --git a/src/win32_platform.h b/src/win32_platform.h
index 5f781eb0..c0395bb9 100644
--- a/src/win32_platform.h
+++ b/src/win32_platform.h
@@ -77,6 +77,20 @@
 #ifndef WM_DWMCOMPOSITIONCHANGED
  #define WM_DWMCOMPOSITIONCHANGED 0x031E
 #endif
+#ifndef WM_COPYGLOBALDATA
+ #define WM_COPYGLOBALDATA 0x0049
+#endif
+#ifndef MSGFLT_ALLOW
+ #define MSGFLT_ALLOW 1
+#endif
+
+#if defined(__MINGW32__)
+typedef struct tagCHANGEFILTERSTRUCT
+{
+    DWORD cbSize;
+    DWORD ExtStatus;
+} CHANGEFILTERSTRUCT, *PCHANGEFILTERSTRUCT;
+#endif /*__MINGW32__*/
 
 
 //========================================================================
@@ -107,7 +121,9 @@ typedef DWORD (WINAPI * TIMEGETTIME_T) (void);
 
 // user32.dll function pointer typedefs
 typedef BOOL (WINAPI * SETPROCESSDPIAWARE_T)(void);
+typedef BOOL (WINAPI * CHANGEWINDOWMESSAGEFILTEREX_T)(HWND,UINT,DWORD,PCHANGEFILTERSTRUCT);
 #define _glfw_SetProcessDPIAware _glfw.win32.user32.SetProcessDPIAware
+#define _glfw_ChangeWindowMessageFilterEx _glfw.win32.user32.ChangeWindowMessageFilterEx
 
 // dwmapi.dll function pointer typedefs
 typedef HRESULT (WINAPI * DWMISCOMPOSITIONENABLED_T)(BOOL*);
@@ -192,6 +208,7 @@ typedef struct _GLFWlibraryWin32
     struct {
         HINSTANCE       instance;
         SETPROCESSDPIAWARE_T SetProcessDPIAware;
+        CHANGEWINDOWMESSAGEFILTEREX_T ChangeWindowMessageFilterEx;
     } user32;
 
     // dwmapi.dll
diff --git a/src/win32_window.c b/src/win32_window.c
index 3a0073d3..87831d21 100644
--- a/src/win32_window.c
+++ b/src/win32_window.c
@@ -901,6 +901,16 @@ static int createWindow(_GLFWwindow* window,
 
     free(wideTitle);
 
+    if (_glfw_ChangeWindowMessageFilterEx)
+    {
+        _glfw_ChangeWindowMessageFilterEx(window->win32.handle,
+                                        WM_DROPFILES, MSGFLT_ALLOW, NULL);
+        _glfw_ChangeWindowMessageFilterEx(window->win32.handle,
+                                        WM_COPYDATA, MSGFLT_ALLOW, NULL);
+        _glfw_ChangeWindowMessageFilterEx(window->win32.handle,
+                                        WM_COPYGLOBALDATA, MSGFLT_ALLOW, NULL);
+    }
+
     DragAcceptFiles(window->win32.handle, TRUE);
 
     if (!window->win32.handle)