Windows: Make dropped files be opened or attached

Adds QWindowsDropDataObject as a QWindowsOleDataObject subclass
specialized for handling Drag & Drop, which only allows "text/uri-list"
data to be exported as CF_HDROP, to allow files dragged from
Qt applications and dropped into other applications to be recognized as
attachments or opened. Otherwise, files would be imported as URLs and
inserted as local hyperlinks.

[ChangeLog][Important Behavior Changes][Windows] On Windows, a drag
& drop operation of local files URIs, like QListView items backed by a
QFileSystemModel, will result in the attachment or opening of the files
by the target application, instead of the creation of hyperlinks.

Task-number: QTBUG-62662
Change-Id: I51efa4a56574b5e5fb3ee736ede14b5da24caac4
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

4 files changed, 165 insertions, 2 deletions

diff --git a/src/plugins/platforms/windows/qwindowsdrag.cpp b/src/plugins/platforms/windows/qwindowsdrag.cpp
index 857db7a65c..aa6454ef63 100644
--- a/src/plugins/platforms/windows/qwindowsdrag.cpp
+++ b/src/plugins/platforms/windows/qwindowsdrag.cpp
@@ -44,7 +44,7 @@
 #  include "qwindowsclipboard.h"
 #endif
 #include "qwindowsintegration.h"
-#include "qwindowsole.h"
+#include "qwindowsdropdataobject.h"
 #include <QtCore/qt_windows.h>
 #include "qwindowswindow.h"
 #include "qwindowsmousehandler.h"
@@ -673,7 +673,7 @@ Qt::DropAction QWindowsDrag::drag(QDrag *drag)
     QWindowsDrag::m_canceled = false;
     QWindowsOleDropSource *windowDropSource = new QWindowsOleDropSource(this);
     windowDropSource->createCursors();
-    QWindowsOleDataObject *dropDataObject = new QWindowsOleDataObject(dropData);
+    QWindowsDropDataObject *dropDataObject = new QWindowsDropDataObject(dropData);
     const Qt::DropActions possibleActions = drag->supportedActions();
     const DWORD allowedEffects = translateToWinDragEffects(possibleActions);
     qCDebug(lcQpaMime) << '>' << __FUNCTION__ << "possible Actions=0x"
diff --git a/src/plugins/platforms/windows/qwindowsdropdataobject.cpp b/src/plugins/platforms/windows/qwindowsdropdataobject.cpp
new file mode 100644
index 0000000000..bd532ab70e
--- /dev/null
+++ b/src/plugins/platforms/windows/qwindowsdropdataobject.cpp
@@ -0,0 +1,98 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qwindowsdropdataobject.h"
+
+#include <QtCore/QUrl>
+#include <QtCore/QMimeData>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QWindowsDropDataObject
+    \brief QWindowsOleDataObject subclass specialized for handling Drag&Drop.
+
+   Only allows "text/uri-list" data to be exported as CF_HDROP, to allow dropped
+   files to be attached to Office applications (instead of adding an URL link).
+
+    \internal
+    \ingroup qt-lighthouse-win
+*/
+
+QWindowsDropDataObject::QWindowsDropDataObject(QMimeData *mimeData) :
+    QWindowsOleDataObject(mimeData)
+{
+}
+
+QWindowsDropDataObject::~QWindowsDropDataObject()
+{
+}
+
+STDMETHODIMP
+QWindowsDropDataObject::GetData(LPFORMATETC pformatetc, LPSTGMEDIUM pmedium)
+{
+    if (shouldIgnore(pformatetc))
+        return ResultFromScode(DATA_E_FORMATETC);
+
+    return QWindowsOleDataObject::GetData(pformatetc, pmedium);
+}
+
+STDMETHODIMP
+QWindowsDropDataObject::QueryGetData(LPFORMATETC pformatetc)
+{
+    if (shouldIgnore(pformatetc))
+        return ResultFromScode(DATA_E_FORMATETC);
+
+    return QWindowsOleDataObject::QueryGetData(pformatetc);
+}
+
+// If the data is text/uri-list for local files, tell we can only export it as CF_HDROP.
+bool QWindowsDropDataObject::shouldIgnore(LPFORMATETC pformatetc) const
+{
+    QMimeData *dropData = mimeData();
+
+    if (dropData && dropData->hasFormat(QStringLiteral("text/uri-list")) && (pformatetc->cfFormat != CF_HDROP)) {
+        QList<QUrl> urls = dropData->urls();
+        return std::any_of(urls.cbegin(), urls.cend(), [] (const QUrl &u) { return u.isLocalFile(); });
+    }
+
+    return false;
+}
+
+QT_END_NAMESPACE
diff --git a/src/plugins/platforms/windows/qwindowsdropdataobject.h b/src/plugins/platforms/windows/qwindowsdropdataobject.h
new file mode 100644
index 0000000000..5ef72c9336
--- /dev/null
+++ b/src/plugins/platforms/windows/qwindowsdropdataobject.h
@@ -0,0 +1,63 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWINDOWSDROPDATAOBJECT_H
+#define QWINDOWSDROPDATAOBJECT_H
+
+#include "qwindowsole.h"
+
+QT_BEGIN_NAMESPACE
+
+class QWindowsDropDataObject : public QWindowsOleDataObject
+{
+public:
+    explicit QWindowsDropDataObject(QMimeData *mimeData);
+    virtual ~QWindowsDropDataObject();
+
+    // overridden IDataObject methods
+    STDMETHOD(GetData)(LPFORMATETC pformatetcIn, LPSTGMEDIUM pmedium);
+    STDMETHOD(QueryGetData)(LPFORMATETC pformatetc);
+
+private:
+    bool shouldIgnore(LPFORMATETC pformatetc) const;
+};
+
+QT_END_NAMESPACE
+
+#endif // QWINDOWSDROPDATAOBJECT_H
diff --git a/src/plugins/platforms/windows/windows.pri b/src/plugins/platforms/windows/windows.pri
index 3ecd164c74..b7790a66e3 100644
--- a/src/plugins/platforms/windows/windows.pri
+++ b/src/plugins/platforms/windows/windows.pri
@@ -19,6 +19,7 @@ SOURCES += \
     $$PWD/qwindowskeymapper.cpp \
     $$PWD/qwindowsmousehandler.cpp \
     $$PWD/qwindowsole.cpp \
+    $$PWD/qwindowsdropdataobject.cpp \
     $$PWD/qwindowsmime.cpp \
     $$PWD/qwindowsinternalmimedata.cpp \
     $$PWD/qwindowscursor.cpp \
@@ -41,6 +42,7 @@ HEADERS += \
     $$PWD/qwindowsmousehandler.h \
     $$PWD/qtwindowsglobal.h \
     $$PWD/qwindowsole.h \
+    $$PWD/qwindowsdropdataobject.h \
     $$PWD/qwindowsmime.h \
     $$PWD/qwindowsinternalmimedata.h \
     $$PWD/qwindowscursor.h \