d3dcompiler_qt: Directly link the d3dcompiler DLL on WinRT 8.1

The compiler DLL is a system module starting with Windows 8.1, so
directly link to it instead of expecting a packaged DLL. This makes
shader precompilation completely optional on this platform.

Change-Id: I46cd175ac32e4909a518a059721241b1d6e7be17
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>

src/angle/src/d3dcompiler/d3dcompiler.pro

@@ -9,6 +9,11 @@ DEFINES += QT_NO_CAST_FROM_ASCII QT_NO_CAST_TO_ASCII
 SOURCES += main.cpp
 win32:!winrt: LIBS += -lole32
 
+winrt:equals(WINSDK_VER, 8.1) {
+    DEFINES += D3DCOMPILER_LINKED
+    LIBS += -ld3dcompiler
+}
+
 # __stdcall exports get mangled, so use a def file
 DEF_FILE += $${TARGET}.def
 

src/angle/src/d3dcompiler/main.cpp

@@ -52,6 +52,12 @@
 #include <qt_windows.h>
 #include <d3dcommon.h>
 
+#ifdef D3DCOMPILER_LINKED
+namespace D3D {
+#  include <d3dcompiler.h>
+}
+#endif // D3DCOMPILER_LINKED
+
 Q_LOGGING_CATEGORY(QT_D3DCOMPILER, "qt.angle.d3dcompiler")
 
 namespace D3DCompiler {
@@ -127,6 +133,7 @@ private:
 
 static bool loadCompiler()
 {
+#ifndef D3DCOMPILER_LINKED
     static HMODULE d3dcompiler = 0;
     if (!d3dcompiler) {
         const wchar_t *dllNames[] = {
@@ -157,7 +164,9 @@ static bool loadCompiler()
         if (!d3dcompiler)
             qCDebug(QT_D3DCOMPILER) << "Unable to load D3D shader compiler.";
     }
-
+#else // !D3DCOMPILER_LINKED
+    compile = &D3D::D3DCompile;
+#endif // D3DCOMPILER_LINKED
     return bool(compile);
 }