QFileDialogOptions: Expose default name filter setting.

Move the bool QFileDialogPrivate::defaultFileTypes to QFileDialogOptions
as defaultNameFilters and add a static function returning the
translated default filter string. Let QFileDialogOptions::nameFilters()
return the default filter until a value has been set.

This removes the need for special handling for empty filter lists
in the QPA plugins. As a side effect, Qt Quick Controls's FileDialog
will then also default to "All files" if no filters have been set.

Task-number: QTBUG-50644
Change-Id: I9ba271a472d4fa03767b540ef6f1399f5ca4408e
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@theqtcompany.com>

src/gui/kernel/qplatformdialoghelper.cpp

@@ -39,6 +39,7 @@
 
 #include "qplatformdialoghelper.h"
 
+#include <QtCore/QCoreApplication>
 #include <QtCore/QVariant>
 #include <QtCore/QSharedData>
 #include <QtCore/QSettings>
@@ -411,7 +412,8 @@ public:
         viewMode(QFileDialogOptions::Detail),
         fileMode(QFileDialogOptions::AnyFile),
         acceptMode(QFileDialogOptions::AcceptOpen),
-        filters(QDir::AllEntries | QDir::NoDotAndDotDot | QDir::AllDirs)
+        filters(QDir::AllEntries | QDir::NoDotAndDotDot | QDir::AllDirs),
+        useDefaultNameFilters(true)
     {}
 
     QFileDialogOptions::FileDialogOptions options;
@@ -423,6 +425,7 @@ public:
     QString labels[QFileDialogOptions::DialogLabelCount];
     QDir::Filters filters;
     QList<QUrl> sidebarUrls;
+    bool useDefaultNameFilters;
     QStringList nameFilters;
     QStringList mimeTypeFilters;
     QString defaultSuffix;
@@ -534,14 +537,48 @@ QList<QUrl> QFileDialogOptions::sidebarUrls() const
     return d->sidebarUrls;
 }
 
+/*!
+    \since 5.7
+    \internal
+    The bool property useDefaultNameFilters indicates that no name filters have been
+    set or that they are equivalent to \gui{All Files (*)}. If it is true, the
+    platform can choose to hide the filter combo box.
+
+    \sa defaultNameFilterString().
+*/
+bool QFileDialogOptions::useDefaultNameFilters() const
+{
+    return d->useDefaultNameFilters;
+}
+
+void QFileDialogOptions::setUseDefaultNameFilters(bool dnf)
+{
+    d->useDefaultNameFilters = dnf;
+}
+
 void QFileDialogOptions::setNameFilters(const QStringList &filters)
 {
+    d->useDefaultNameFilters = filters.size() == 1
+        && filters.first() == QFileDialogOptions::defaultNameFilterString();
     d->nameFilters = filters;
 }
 
 QStringList QFileDialogOptions::nameFilters() const
 {
-    return d->nameFilters;
+    return d->useDefaultNameFilters ?
+        QStringList(QFileDialogOptions::defaultNameFilterString()) : d->nameFilters;
+}
+
+/*!
+    \since 5.6
+    \internal
+    \return The translated default name filter string (\gui{All Files (*)}).
+    \sa defaultNameFilters(), nameFilters()
+*/
+
+QString QFileDialogOptions::defaultNameFilterString()
+{
+    return QCoreApplication::translate("QFileDialog", "All Files (*)");
 }
 
 void QFileDialogOptions::setMimeTypeFilters(const QStringList &filters)

src/gui/kernel/qplatformdialoghelper.h

@@ -349,6 +349,9 @@ public:
     void setSidebarUrls(const QList<QUrl> &urls);
     QList<QUrl> sidebarUrls() const;
 
+    bool useDefaultNameFilters() const;
+    void setUseDefaultNameFilters(bool d);
+
     void setNameFilters(const QStringList &filters);
     QStringList nameFilters() const;
 
@@ -377,6 +380,8 @@ public:
     void setSupportedSchemes(const QStringList &schemes);
     QStringList supportedSchemes() const;
 
+    static QString defaultNameFilterString();
+
 private:
     QSharedDataPointer<QFileDialogOptionsPrivate> d;
 };

src/widgets/dialogs/qfiledialog.cpp

@@ -532,7 +532,6 @@ QFileDialogPrivate::QFileDialogPrivate()
         deleteAction(0),
         showHiddenAction(0),
         useDefaultCaption(true),
-        defaultFileTypes(true),
         qFileDialogUi(0),
         options(new QFileDialogOptions)
 {
@@ -663,8 +662,8 @@ void QFileDialogPrivate::retranslateStrings()
 {
     Q_Q(QFileDialog);
     /* WIDGETS */
-    if (defaultFileTypes)
-        q->setNameFilter(QFileDialog::tr("All Files (*)"));
+    if (options->useDefaultNameFilters())
+        q->setNameFilter(QFileDialogOptions::defaultNameFilterString());
     if (nativeDialogInUse)
         return;
 
@@ -1400,7 +1399,6 @@ QStringList qt_strip_filters(const QStringList &filters)
 void QFileDialog::setNameFilters(const QStringList &filters)
 {
     Q_D(QFileDialog);
-    d->defaultFileTypes = (filters == QStringList(QFileDialog::tr("All Files (*)")));
     QStringList cleanedFilters;
     const int numFilters = filters.count();
     cleanedFilters.reserve(numFilters);

src/widgets/dialogs/qfiledialog_p.h

@@ -250,7 +250,6 @@ public:
     QAction *newFolderAction;
 
     bool useDefaultCaption;
-    bool defaultFileTypes;
 
     // setVisible_sys returns true if it ends up showing a native
     // dialog. Returning false means that a non-native dialog must be