From b55f88caba339a49bf0ebabfa324dde523c2b866 Mon Sep 17 00:00:00 2001
From: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Date: Wed, 12 Nov 2014 09:13:23 +0100
Subject: [PATCH] Windows: Correctly associate IME contexts.

Associate a 0-context with the window if IME is disabled, store
this state as a flag to QWindowsWindow. Associate default context
again when enabled window gains focus.

Task-number: QTBUG-40691
Change-Id: I78d5494a05f93a39e245ca7c096d45445e684ea8
Reviewed-by: Liang Qi <liang.qi@theqtcompany.com>
---
 .../windows/qwindowsinputcontext.cpp          | 23 ++++++++++++++++++-
 .../platforms/windows/qwindowsinputcontext.h  |  1 +
 .../platforms/windows/qwindowswindow.h        |  3 ++-
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowsinputcontext.cpp b/src/plugins/platforms/windows/qwindowsinputcontext.cpp
index b1259d757e..94a27d146f 100644
--- a/src/plugins/platforms/windows/qwindowsinputcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowsinputcontext.cpp
@@ -145,6 +145,7 @@ static inline void imeNotifyCancelComposition(HWND hwnd)
 */
 
 
+HIMC QWindowsInputContext::m_defaultContext = 0;
 
 QWindowsInputContext::CompositionContext::CompositionContext() :
     hwnd(0), haveCaret(false), position(0), isComposing(false)
@@ -199,13 +200,33 @@ void QWindowsInputContext::reset()
     doneContext();
 }
 
-void QWindowsInputContext::setFocusObject(QObject *)
+void QWindowsInputContext::setFocusObject(QObject *object)
 {
     // ### fixme: On Windows 8.1, it has been observed that the Input context
     // remains active when this happens resulting in a lock-up. Consecutive
     // key events still have VK_PROCESSKEY set and are thus ignored.
     if (m_compositionContext.isComposing)
         imeNotifyCancelComposition(m_compositionContext.hwnd);
+
+    const QWindow *window = QGuiApplication::focusWindow();
+    if (object && window) {
+        QWindowsWindow *platformWindow = QWindowsWindow::baseWindowOf(window);
+        if (inputMethodAccepted()) {
+            // Re-enable IME by associating default context saved on first disabling.
+            if (platformWindow->testFlag(QWindowsWindow::InputMethodDisabled)) {
+                ImmAssociateContext(platformWindow->handle(), QWindowsInputContext::m_defaultContext);
+                platformWindow->clearFlag(QWindowsWindow::InputMethodDisabled);
+            }
+        } else {
+            // Disable IME by associating 0 context. Store context first time.
+            if (!platformWindow->testFlag(QWindowsWindow::InputMethodDisabled)) {
+                const HIMC oldImC = ImmAssociateContext(platformWindow->handle(), 0);
+                platformWindow->setFlag(QWindowsWindow::InputMethodDisabled);
+                if (!QWindowsInputContext::m_defaultContext && oldImC)
+                    QWindowsInputContext::m_defaultContext = oldImC;
+            }
+        }
+    }
 }
 
 /*!
diff --git a/src/plugins/platforms/windows/qwindowsinputcontext.h b/src/plugins/platforms/windows/qwindowsinputcontext.h
index 39880a2e86..86243952ec 100644
--- a/src/plugins/platforms/windows/qwindowsinputcontext.h
+++ b/src/plugins/platforms/windows/qwindowsinputcontext.h
@@ -88,6 +88,7 @@ private:
     void endContextComposition();
 
     const DWORD m_WM_MSIME_MOUSE;
+    static HIMC m_defaultContext;
     CompositionContext m_compositionContext;
     bool m_endCompositionRecursionGuard;
 };
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index 71debf2476..edba992b19 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -138,7 +138,8 @@ public:
         Exposed = 0x10000,
         WithinCreate = 0x20000,
         WithinMaximize = 0x40000,
-        MaximizeToFullScreen = 0x80000
+        MaximizeToFullScreen = 0x80000,
+        InputMethodDisabled =0x100000
     };
 
     QWindowsWindow(QWindow *window, const QWindowsWindowData &data);