Windows: Run on Windows XP.

Replace Q_ASSERT() on missing functions from User32.dll by
qFatal() with error message. Do not check "UpdateLayeredWindowIndirect"
as it was introduced with Windows Vista.

Task-number: QTBUG-23351

Change-Id: I0064611351c687f0c3c6e13156dd534b9f7a5d75
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

2 files changed, 4 insertions, 5 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index 70d879e19f..3600c66114 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -164,11 +164,10 @@ void QWindowsUser32DLL::init()
     // MinGW (g++ 3.4.5) accepts only C casts.
     setLayeredWindowAttributes = (SetLayeredWindowAttributes)(library.resolve("SetLayeredWindowAttributes"));
     updateLayeredWindow = (UpdateLayeredWindow)(library.resolve("UpdateLayeredWindow"));
-    updateLayeredWindowIndirect = (UpdateLayeredWindowIndirect)(library.resolve("UpdateLayeredWindowIndirect"));
-
-    Q_ASSERT(setLayeredWindowAttributes && updateLayeredWindow
-             && updateLayeredWindowIndirect);
+    if (!setLayeredWindowAttributes || !updateLayeredWindow)
+        qFatal("This version of Windows is not supported (User32.dll is missing the symbols 'SetLayeredWindowAttributes', 'UpdateLayeredWindow').");
 
+    updateLayeredWindowIndirect = (UpdateLayeredWindowIndirect)(library.resolve("UpdateLayeredWindowIndirect"));
     isHungAppWindow = (IsHungAppWindow)library.resolve("IsHungAppWindow");
 }
 
diff --git a/src/plugins/platforms/windows/qwindowscontext.h b/src/plugins/platforms/windows/qwindowscontext.h
index db57f7c097..9a8acbbb51 100644
--- a/src/plugins/platforms/windows/qwindowscontext.h
+++ b/src/plugins/platforms/windows/qwindowscontext.h
@@ -77,9 +77,9 @@ struct QWindowsUser32DLL
     // Functions missing in Q_CC_GNU stub libraries.
     SetLayeredWindowAttributes setLayeredWindowAttributes;
     UpdateLayeredWindow updateLayeredWindow;
-    UpdateLayeredWindowIndirect updateLayeredWindowIndirect;
 
     // Functions missing in older versions of Windows
+    UpdateLayeredWindowIndirect updateLayeredWindowIndirect;
     IsHungAppWindow isHungAppWindow;
 
     // Touch functions from Windows 7 onwards (also for use with Q_CC_MSVC).