winrt: Clean up platform message dialog helper

- Remove "Platform" from class name for consistency
- Use ComPtr and HRESULT checking where missing
- Use UICommand ID class to reduce callback complexity
- Use dialog completed callback to fix failed repeated dialog opening

These changes have been tested with the QtQuick.Dialogs message dialog
example, and all features appear to be working. Note that the WinRT
dialog supports a maximum of three buttons, though, and a warning is
printed if this number is exceeded.

Similarly to Android, the native hooks can be now be disabled by
using qputenv("QT_USE_WINRT_NATIVE_DIALOGS", "0").

Task-number: QTBUG-38115
Task-number: QTBUG-39868
Change-Id: I9943c7c11bd640790db68219cefdca1a680e96ec
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/src/plugins/platforms/winrt/qwinrttheme.cpp b/src/plugins/platforms/winrt/qwinrttheme.cpp
index 65ed9440b2..f9c2e21676 100644
--- a/src/plugins/platforms/winrt/qwinrttheme.cpp
+++ b/src/plugins/platforms/winrt/qwinrttheme.cpp
@@ -40,7 +40,7 @@
 ****************************************************************************/
 
 #include "qwinrttheme.h"
-#include "qwinrtplatformmessagedialoghelper.h"
+#include "qwinrtmessagedialoghelper.h"
 
 #include <QtCore/qfunctions_winrt.h>
 #include <QtGui/QPalette>
@@ -131,8 +131,11 @@ QWinRTTheme::QWinRTTheme()
 
 bool QWinRTTheme::usePlatformNativeDialog(DialogType type) const
 {
+    static bool useNativeDialogs = qEnvironmentVariableIsSet("QT_USE_WINRT_NATIVE_DIALOGS")
+            ? qgetenv("QT_USE_WINRT_NATIVE_DIALOGS").toInt() : true;
+
     if (type == MessageDialog)
-        return true;
+        return useNativeDialogs;
     return false;
 }
 
@@ -140,7 +143,7 @@ QPlatformDialogHelper *QWinRTTheme::createPlatformDialogHelper(DialogType type)
 {
     switch (type) {
     case MessageDialog:
-        return new QWinRTPlatformMessageDialogHelper;
+        return new QWinRTMessageDialogHelper(this);
     default:
         break;
     }