Add a platform theme option to affect SH_UnderlineShortcut

The style hint SH_UnderlineShortcut can now be turned on/off via the
platform theme.

No change in functionality so far on any platform, this behaves the
same way it did before the change. The change just adds a possibility
for platforms to redefine the default underlining behavior.

Task-number: QTBUG-76587
Change-Id: Ibda104f1b733371da19825b96e73c22f42faf853
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/gui/kernel/qplatformintegration.cpp

@@ -416,6 +416,8 @@ QVariant QPlatformIntegration::styleHint(StyleHint hint) const
         return QPlatformTheme::defaultThemeHint(QPlatformTheme::FlickMaximumVelocity);
     case FlickDeceleration:
         return QPlatformTheme::defaultThemeHint(QPlatformTheme::FlickDeceleration);
+    case UnderlineShortcut:
+        return true;
     }
 
     return 0;

src/gui/kernel/qplatformintegration.h

@@ -164,7 +164,8 @@ public:
         MouseDoubleClickDistance,
         FlickStartDistance,
         FlickMaximumVelocity,
-        FlickDeceleration
+        FlickDeceleration,
+        UnderlineShortcut,
     };
 
     virtual QVariant styleHint(StyleHint hint) const;

src/gui/kernel/qplatformtheme.cpp

@@ -525,6 +525,8 @@ QVariant QPlatformTheme::themeHint(ThemeHint hint) const
         return QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::FlickMaximumVelocity);
     case QPlatformTheme::FlickDeceleration:
         return QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::FlickDeceleration);
+    case QPlatformTheme::UnderlineShortcut:
+        return QGuiApplicationPrivate::platformIntegration()->styleHint(QPlatformIntegration::UnderlineShortcut);
     default:
         return QPlatformTheme::defaultThemeHint(hint);
     }
@@ -637,7 +639,10 @@ QVariant QPlatformTheme::defaultThemeHint(ThemeHint hint)
         return QVariant(QString());
     case MouseCursorSize:
         return QVariant(QSize(16, 16));
+    case UnderlineShortcut:
+        return true;
     }
+
     return QVariant();
 }
 

src/gui/kernel/qplatformtheme.h

@@ -95,7 +95,8 @@ public:
         FlickDeceleration,
         MenuBarFocusOnAltPressRelease,
         MouseCursorTheme,
-        MouseCursorSize
+        MouseCursorSize,
+        UnderlineShortcut,
     };
     Q_ENUM(ThemeHint)
 

src/widgets/styles/qcommonstyle.cpp

@@ -5156,9 +5156,12 @@ int QCommonStyle::styleHint(StyleHint sh, const QStyleOption *opt, const QWidget
         ret = 1;
         break;
 
-    case SH_UnderlineShortcut:
+    case SH_UnderlineShortcut: {
-        ret = 1;
+        const QPlatformTheme *theme = QGuiApplicationPrivate::platformTheme();
+        ret = theme ? theme->themeHint(QPlatformTheme::UnderlineShortcut).toInt()
+                    : QPlatformTheme::defaultThemeHint(QPlatformTheme::UnderlineShortcut).toInt();
         break;
+    }
 
     case SH_SpinBox_ClickAutoRepeatRate:
         ret = 150;