tdf#122752 gtk3_kde5: Use non-native fpicker for non-Plasma desktops

Adding the custom widgets to the native dialog currently depends
on the native dialog using a KFileWidget, which is just the case for
the native QFileDialog implementation on Plasma/KDE5.

In order not to lose custom controls for non-Plasma desktops,
fall back to using the non-native QFileDialog there and adding
the custom controls to its layout.
This was mostly taken over from Qt5FileDialog.
(This is a similar approach as that taken for the kde5 VCL plugin
in https://gerrit.libreoffice.org/#/c/67106/ ).

Adding the controls to the layout returned by 'QFileDialog::layout()'
cannot be used for the native dialog as well, since a nullptr is
returned in this case.

From QFileDialog doc:

> By default, a platform-native file dialog will be used if the platform
> has one. In that case, the widgets which would otherwise be used to
> construct the dialog will not be instantiated, so related accessors such
> as layout() and itemDelegate() will return null. You can set the
> DontUseNativeDialog option to ensure that the widget-based
> implementation will be used instead of the native dialog.

Change-Id: I75fbe7731da28d0dc7df878f4c57e141d4d89902
Reviewed-on: https://gerrit.libreoffice.org/67111
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Michael Weghorn <m.weghorn@posteo.de>

2 files changed, 27 insertions, 1 deletions

diff --git a/vcl/unx/gtk3_kde5/kde5_filepicker.cxx b/vcl/unx/gtk3_kde5/kde5_filepicker.cxx
index 42e278aa3d0e..33f64ad0aa18 100644
--- a/vcl/unx/gtk3_kde5/kde5_filepicker.cxx
+++ b/vcl/unx/gtk3_kde5/kde5_filepicker.cxx
@@ -17,6 +17,8 @@
  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  */
 
+#include <vcl/svapp.hxx>
+
 #include "kde5_filepicker.hxx"
 
 #include <KWindowSystem>
@@ -57,7 +59,7 @@ KDE5FilePicker::KDE5FilePicker(QObject* parent)
     connect(_dialog, &QFileDialog::filterSelected, this, &KDE5FilePicker::filterChanged);
     connect(_dialog, &QFileDialog::fileSelected, this, &KDE5FilePicker::selectionChanged);
 
-    qApp->installEventFilter(this);
+    setupCustomWidgets();
 }
 
 void KDE5FilePicker::enableFolderMode()
@@ -232,6 +234,28 @@ void KDE5FilePicker::initialize(bool saveDialog)
 
 void KDE5FilePicker::setWinId(sal_uIntPtr winId) { _winId = winId; }
 
+void KDE5FilePicker::setupCustomWidgets()
+{
+    // When using the platform-native Plasma/KDE5 file picker, we currently rely on KFileWidget
+    // being present to add the custom controls visible (s. 'eventFilter' method).
+    // Since this doesn't work for other desktop environments, use a non-native
+    // dialog there in order not to lose the custom controls and insert the custom
+    // widget in the layout returned by QFileDialog::layout()
+    // (which returns nullptr for native file dialogs)
+    if (Application::GetDesktopEnvironment() == "KDE5")
+    {
+        qApp->installEventFilter(this);
+    }
+    else
+    {
+        _dialog->setOption(QFileDialog::DontUseNativeDialog);
+        QGridLayout* pLayout = static_cast<QGridLayout*>(_dialog->layout());
+        assert(pLayout);
+        const int row = pLayout->rowCount();
+        pLayout->addWidget(_extraControls, row, 1);
+    }
+}
+
 bool KDE5FilePicker::eventFilter(QObject* o, QEvent* e)
 {
     if (e->type() == QEvent::Show && o->isWidgetType())
diff --git a/vcl/unx/gtk3_kde5/kde5_filepicker.hxx b/vcl/unx/gtk3_kde5/kde5_filepicker.hxx
index d999f7bf7a09..c979a5ddcad9 100644
--- a/vcl/unx/gtk3_kde5/kde5_filepicker.hxx
+++ b/vcl/unx/gtk3_kde5/kde5_filepicker.hxx
@@ -98,6 +98,8 @@ public:
 
 private:
     Q_DISABLE_COPY(KDE5FilePicker)
+    // adds the custom controls to the dialog
+    void setupCustomWidgets();
 
 protected:
     bool eventFilter(QObject* watched, QEvent* event) override;