Add capabilities to QPlatformInputContext.

Add a capability enumeration to QPlatformInputContext and
use that to turn off input methods for hidden text depending
on platform support. Disable on Windows.

Task-number: QTBUG-40691
Change-Id: I9909005de1f21316ec8f64e2729f1fffcd37c7c3
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Björn Breitmeyer <bjoern.breitmeyer@kdab.com>
Reviewed-by: Liang Qi <liang.qi@theqtcompany.com>

src/gui/kernel/qguiapplication.cpp

@@ -3400,15 +3400,21 @@ void QGuiApplicationPrivate::_q_updateFocusObject(QObject *object)
 {
     Q_Q(QGuiApplication);
 
+    QPlatformInputContext *inputContext = platformIntegration()->inputContext();
     bool enabled = false;
-    if (object) {
+    if (object && inputContext) {
-        QInputMethodQueryEvent query(Qt::ImEnabled);
+        QInputMethodQueryEvent query(Qt::ImEnabled | Qt::ImHints);
         QGuiApplication::sendEvent(object, &query);
         enabled = query.value(Qt::ImEnabled).toBool();
+        if (enabled) {
+            static const bool supportsHiddenText = inputContext->hasCapability(QPlatformInputContext::HiddenTextCapability);
+            const Qt::InputMethodHints hints = static_cast<Qt::InputMethodHints>(query.value(Qt::ImHints).toInt());
+            if ((hints & Qt::ImhHiddenText) && !supportsHiddenText)
+                enabled = false;
+        }
     }
 
     QPlatformInputContextPrivate::setInputMethodAccepted(enabled);
-    QPlatformInputContext *inputContext = platformIntegration()->inputContext();
     if (inputContext)
         inputContext->setFocusObject(object);
     emit q->focusObjectChanged(object);

src/gui/kernel/qplatforminputcontext.cpp

@@ -91,6 +91,17 @@ bool QPlatformInputContext::isValid() const
     return false;
 }
 
+/*!
+    Returns whether the implementation supports \a capability.
+    \internal
+    \since 5.4
+ */
+bool QPlatformInputContext::hasCapability(Capability capability) const
+{
+    Q_UNUSED(capability)
+    return true;
+}
+
 /*!
     Method to be called when input method needs to be reset. Called by QInputMethod::reset().
     No further QInputMethodEvents should be sent as response.

src/gui/kernel/qplatforminputcontext.h

@@ -55,10 +55,15 @@ class Q_GUI_EXPORT QPlatformInputContext : public QObject
     Q_DECLARE_PRIVATE(QPlatformInputContext)
 
 public:
+    enum Capability {
+        HiddenTextCapability = 0x1
+    };
+
     QPlatformInputContext();
     virtual ~QPlatformInputContext();
 
     virtual bool isValid() const;
+    virtual bool hasCapability(Capability capability) const;
 
     virtual void reset();
     virtual void commit();

src/plugins/platforms/windows/qwindowsinputcontext.cpp

@@ -163,6 +163,21 @@ QWindowsInputContext::~QWindowsInputContext()
 {
 }
 
+bool QWindowsInputContext::hasCapability(Capability capability) const
+{
+    switch (capability) {
+    case QPlatformInputContext::HiddenTextCapability:
+#ifndef Q_OS_WINCE
+        return false; // QTBUG-40691, do not show IME on desktop for password entry fields.
+#else
+        break; // Windows CE: Show software keyboard.
+#endif
+    default:
+        break;
+    }
+    return true;
+}
+
 /*!
     \brief Cancels a composition.
 */

src/plugins/platforms/windows/qwindowsinputcontext.h

@@ -62,6 +62,7 @@ public:
     explicit QWindowsInputContext();
     ~QWindowsInputContext();
 
+    bool hasCapability(Capability capability) const Q_DECL_OVERRIDE;
     void reset() Q_DECL_OVERRIDE;
     void update(Qt::InputMethodQueries) Q_DECL_OVERRIDE;
     void invokeAction(QInputMethod::Action, int cursorPosition) Q_DECL_OVERRIDE;