Automatically reflect new input context input direction when locale changes

All platforms except Wayland fail to check for input direction change
when the locale changes, and only emitLocaleChanged.

We can simplify this for the platforms by checking if the new
locale caused a change in input direction, and if so emit
inputDirectionChanged on their behalf.

Change-Id: I84d8df9392db5e716f5c277d0cc9e17e5a21783f
Reviewed-by: Liang Qi <liang.qi@qt.io>

src/gui/kernel/qplatforminputcontext.cpp

@@ -47,6 +47,11 @@ QT_BEGIN_NAMESPACE
 QPlatformInputContext::QPlatformInputContext()
     : QObject(*(new QPlatformInputContextPrivate))
 {
+    // Delay initialization of cached input direction
+    // until super class has finished constructing.
+    QMetaObject::invokeMethod(this, [this]{
+        m_inputDirection = inputDirection();
+    }, Qt::QueuedConnection);
 }
 
 /*!
@@ -198,6 +203,9 @@ QLocale QPlatformInputContext::locale() const
 void QPlatformInputContext::emitLocaleChanged()
 {
     emit QGuiApplication::inputMethod()->localeChanged();
+
+    // Changing the locale might have updated the input direction
+    emitInputDirectionChanged(inputDirection());
 }
 
 Qt::LayoutDirection QPlatformInputContext::inputDirection() const
@@ -207,7 +215,11 @@ Qt::LayoutDirection QPlatformInputContext::inputDirection() const
 
 void QPlatformInputContext::emitInputDirectionChanged(Qt::LayoutDirection newDirection)
 {
+    if (newDirection == m_inputDirection)
+        return;
+
     emit QGuiApplication::inputMethod()->inputDirectionChanged(newDirection);
+    m_inputDirection = newDirection;
 }
 
 /*!

src/gui/kernel/qplatforminputcontext.h

@@ -72,6 +72,8 @@ private:
     friend class QGuiApplication;
     friend class QGuiApplicationPrivate;
     friend class QInputMethod;
+
+    Qt::LayoutDirection m_inputDirection;
 };
 
 QT_END_NAMESPACE