From 2715e0929e34d1efcbab566f83379efcd4e4dc58 Mon Sep 17 00:00:00 2001
From: dcnieho <dcnieho@7f0cb862-5218-0410-a997-914c9d46530a>
Date: Sat, 9 Nov 2013 05:33:02 +0000
Subject: [PATCH] Fixing problem with non-client area becoming unresponsive on
 Windows due to mouse capture that isn't released. Thanks Philipp Kutin (on
 list!) for figuring this out and proposing a solution. -> It appears
 GetAsyncKeyState's return can be non-zero even when the queried key is not
 pressed

git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk@1627 7f0cb862-5218-0410-a997-914c9d46530a
---
 freeglut/freeglut/src/mswin/fg_main_mswin.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/freeglut/freeglut/src/mswin/fg_main_mswin.c b/freeglut/freeglut/src/mswin/fg_main_mswin.c
index 8162a5f..09e397f 100644
--- a/freeglut/freeglut/src/mswin/fg_main_mswin.c
+++ b/freeglut/freeglut/src/mswin/fg_main_mswin.c
@@ -578,6 +578,18 @@ static int fgPlatformGetModifiers (void)
             ( GetKeyState( VK_RMENU    ) < 0 )) ? GLUT_ACTIVE_ALT   : 0 );
 }
 
+/* Check whether a button (VK_*BUTTON) is currently depressed. Returns
+ * non-zero (not necessarily 1) if yes. */
+static SHORT fgGetAsyncKeyState(int vKey)
+{
+    /* MSDN says: "If the most significant bit is set, the key is down, and if
+     * the least significant bit is set, the key was pressed after the previous
+     * call to GetAsyncKeyState." This behavior cannot be relied upon however.
+     * Remove this bit so that we can simply test with ! if key is up.
+     */
+    return GetAsyncKeyState(vKey) & ~1;
+}
+
 static LRESULT fghWindowProcKeyPress(SFG_Window *window, UINT uMsg, GLboolean keydown, WPARAM wParam, LPARAM lParam)
 {
     static unsigned char lControl = 0, lShift = 0, lAlt = 0,
@@ -629,12 +641,12 @@ static LRESULT fghWindowProcKeyPress(SFG_Window *window, UINT uMsg, GLboolean ke
      * so when we get an alt, shift or control keypress here, we manually check whether it was the left or the right
      */
 #define ASYNC_KEY_EVENT(winKey,glutKey,keyStateVar)\
-    if (!keyStateVar && GetAsyncKeyState ( winKey ))\
+    if (!keyStateVar && fgGetAsyncKeyState ( winKey ))\
     {\
         keypress   = glutKey;\
         keyStateVar = 1;\
     }\
-    else if (keyStateVar && !GetAsyncKeyState ( winKey ))\
+    else if (keyStateVar && !fgGetAsyncKeyState ( winKey ))\
     {\
         keypress   = glutKey;\
         keyStateVar = 0;\
@@ -1237,7 +1249,7 @@ LRESULT CALLBACK fgPlatformWindowProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPAR
                 SetCapture ( window->Window.Handle ) ;
             setCaptureActive = 1; /* Set to false in WM_CAPTURECHANGED handler */
         }
-        else if (!GetAsyncKeyState(VK_LBUTTON) && !GetAsyncKeyState(VK_MBUTTON) && !GetAsyncKeyState(VK_RBUTTON))
+        else if (!fgGetAsyncKeyState(VK_LBUTTON) && !fgGetAsyncKeyState(VK_MBUTTON) && !fgGetAsyncKeyState(VK_RBUTTON))
           /* Make sure all mouse buttons are released before releasing capture */
           ReleaseCapture () ;