Correct usage of GetVersion() windows calls. Review: http://codereview.appspot.com/4579049

src/libEGL/Surface.cpp

@@ -22,6 +22,23 @@
 
 namespace egl
 {
+
+namespace
+{
+const int versionWindowsVista = MAKEWORD(0x00, 0x06);
+const int versionWindows7 = MAKEWORD(0x01, 0x06);
+
+// Return the version of the operating system in a format suitable for ordering
+// comparison.
+int getComparableOSVersion()
+{
+    DWORD version = GetVersion();
+    int majorVersion = LOBYTE(LOWORD(version));
+    int minorVersion = HIBYTE(LOWORD(version));
+    return MAKEWORD(minorVersion, majorVersion);
+}
+}
+
 Surface::Surface(Display *display, const Config *config, HWND window) 
     : mDisplay(display), mConfig(config), mWindow(window)
 {
@@ -78,7 +95,7 @@ bool Surface::initialize()
     // Modify present parameters for this window, if we are composited,
     // to minimize the amount of queuing done by DWM between our calls to
     // present and the actual screen.
-    if (mWindow && (LOWORD(GetVersion()) >= 0x60)) {
+    if (mWindow && (getComparableOSVersion() >= versionWindowsVista)) {
       BOOL isComposited;
       HRESULT result = DwmIsCompositionEnabled(&isComposited);
       if (SUCCEEDED(result) && isComposited) {
@@ -165,7 +182,7 @@ bool Surface::resetSwapChain(int backbufferWidth, int backbufferHeight)
     D3DPRESENT_PARAMETERS presentParameters = {0};
     HRESULT result;
 
-    bool useFlipEx = (LOWORD(GetVersion()) >= 0x61) && mDisplay->isD3d9ExDevice();
+    bool useFlipEx = (getComparableOSVersion() >= versionWindows7) && mDisplay->isD3d9ExDevice();
 
     // FlipEx causes unseemly stretching when resizing windows AND when one
     // draws outside of the WM_PAINT callback. While this is seldom a problem in