Material: use proper layout of the buttons in the DialogButtonBox

Instead of using system button layout, use layout from macOS, which
better fits the Material Design guidelines and also used in the Android
QPA plugin.

Task-number: QTBUG-58060
Change-Id: I06381219b5f1ad0a32742487fd314a8017d82dfc
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

3 files changed, 27 insertions, 1 deletions

diff --git a/src/imports/controls/material/qquickmaterialtheme.cpp b/src/imports/controls/material/qquickmaterialtheme.cpp
index 63def7a5..3ea41779 100644
--- a/src/imports/controls/material/qquickmaterialtheme.cpp
+++ b/src/imports/controls/material/qquickmaterialtheme.cpp
@@ -36,6 +36,7 @@
 
 #include "qquickmaterialtheme_p.h"
 
+#include <QtGui/qpa/qplatformdialoghelper.h>
 #include <QtGui/qfont.h>
 #include <QtGui/qfontinfo.h>
 
@@ -105,4 +106,21 @@ const QFont *QQuickMaterialTheme::font(QPlatformTheme::Font type) const
     }
 }
 
+QVariant QQuickMaterialTheme::themeHint(ThemeHint hint) const
+{
+    switch (hint) {
+    case QPlatformTheme::DialogButtonBoxLayout:
+        // https://material.io/guidelines/components/dialogs.html#dialogs-specs
+        // As per spec, affirmative actions are placed to the right, dismissive
+        // actions are placed directly to the left of affirmative actions.
+        // In the Android sources, there are additional type of actions -
+        // neutral, which are placed to the left.
+        // Rules for macOS seems to be the most suitable here and are also used
+        // in the Android QPA plugin.
+        return QVariant(QPlatformDialogHelper::MacLayout);
+    default:
+        return QQuickProxyTheme::themeHint(hint);
+    }
+}
+
 QT_END_NAMESPACE
diff --git a/src/imports/controls/material/qquickmaterialtheme_p.h b/src/imports/controls/material/qquickmaterialtheme_p.h
index 828ca83a..d505d4ff 100644
--- a/src/imports/controls/material/qquickmaterialtheme_p.h
+++ b/src/imports/controls/material/qquickmaterialtheme_p.h
@@ -48,6 +48,7 @@
 // We mean it.
 //
 
+#include <QtCore/qvariant.h>
 #include <QtGui/qfont.h>
 #include <QtQuickControls2/private/qquickproxytheme_p.h>
 
@@ -60,6 +61,8 @@ public:
 
     const QFont *font(Font type = SystemFont) const override;
 
+    QVariant themeHint(ThemeHint hint) const override;
+
 private:
     QFont systemFont;
     QFont buttonFont;
diff --git a/src/quicktemplates2/qquickdialogbuttonbox.cpp b/src/quicktemplates2/qquickdialogbuttonbox.cpp
index 40b1e2c7..b85e85c8 100644
--- a/src/quicktemplates2/qquickdialogbuttonbox.cpp
+++ b/src/quicktemplates2/qquickdialogbuttonbox.cpp
@@ -258,7 +258,12 @@ void QQuickDialogButtonBoxPrivate::updateLayout()
 
             return firstRole != QPlatformDialogHelper::InvalidRole;
         }
-        const int *m_layout = QPlatformDialogHelper::buttonLayout();
+        static const int *themeButtonLayout()
+        {
+            const int hint = QGuiApplicationPrivate::platformTheme()->themeHint(QPlatformTheme::DialogButtonBoxLayout).toInt();
+            return QPlatformDialogHelper::buttonLayout(Qt::Horizontal, static_cast<QPlatformDialogHelper::ButtonLayout>(hint));
+        }
+        const int *m_layout = themeButtonLayout();
     };
 
     std::sort(buttons.begin(), buttons.end(), ButtonLayout());