From 34b066db62d807655f2f39d5eb173a771cbe5b10 Mon Sep 17 00:00:00 2001
From: Aleix Pol <aleixpol@kde.org>
Date: Wed, 10 Mar 2021 01:09:13 +0100
Subject: client: Allow QWaylandInputContext to accept composed key
 combinations

At the moment, we are forcing user to choose to either compose or use
the text-input channel. This patch brings some of the QComposeInputContext
functionality in order to let applications understand dead key
combinations like they are supposed to.

Having it in QWaylandInputContext rather than in QWaylandInputDevice
should solve the problems 3aedd01271dc4f4a13103d632df224971ab2b6df had
with 57c4af2b18c0fb1d266b245a107fa6cb876b9d9e, because we are doing it
in the input context rather than before. This way, if the user is
overriding the input method (e.g. by setting QT_IM_MODULE), all the key
strokes will still be properly forwarded to the module to use.

This in turn allows us to solve https://bugs.kde.org/show_bug.cgi?id=411729
and https://bugs.kde.org/show_bug.cgi?id=405388 since we don't need to
choose anymore between physical and virual keyboards anymore.

Change-Id: I8601f5d7ae21edf4b3a1191fa75877286e505588
Reviewed-by: David Edmundson <davidedmundson@kde.org>
(cherry picked from commit cca1b94190a094b5d1d7ce492b6533e2d330c5e8)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/client/qwaylandinputcontext.cpp | 95 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 94 insertions(+), 1 deletion(-)

(limited to 'src/client/qwaylandinputcontext.cpp')

diff --git a/src/client/qwaylandinputcontext.cpp b/src/client/qwaylandinputcontext.cpp
index d7d168a75..923950fe9 100644
--- a/src/client/qwaylandinputcontext.cpp
+++ b/src/client/qwaylandinputcontext.cpp
@@ -406,6 +406,8 @@ bool QWaylandInputContext::isValid() const
 void QWaylandInputContext::reset()
 {
     qCDebug(qLcQpaInputMethods) << Q_FUNC_INFO;
+    if (m_composeState)
+        xkb_compose_state_reset(m_composeState);
 
     QPlatformInputContext::reset();
 
@@ -526,9 +528,14 @@ Qt::LayoutDirection QWaylandInputContext::inputDirection() const
     return textInput()->inputDirection();
 }
 
-void QWaylandInputContext::setFocusObject(QObject *)
+void QWaylandInputContext::setFocusObject(QObject *object)
 {
     qCDebug(qLcQpaInputMethods) << Q_FUNC_INFO;
+#if QT_CONFIG(xkbcommon)
+    m_focusObject = object;
+#else
+    Q_UNUSED(object);
+#endif
 
     if (!textInput())
         return;
@@ -561,6 +568,92 @@ QWaylandTextInput *QWaylandInputContext::textInput() const
     return mDisplay->defaultInputDevice()->textInput();
 }
 
+#if QT_CONFIG(xkbcommon)
+
+void QWaylandInputContext::ensureInitialized()
+{
+    if (m_initialized)
+        return;
+
+    if (!m_XkbContext) {
+        qCWarning(qLcQpaInputMethods) << "error: xkb context has not been set on" << metaObject()->className();
+        return;
+    }
+
+    m_initialized = true;
+    const char *locale = setlocale(LC_CTYPE, "");
+    if (!locale)
+        locale = setlocale(LC_CTYPE, nullptr);
+    qCDebug(qLcQpaInputMethods) << "detected locale (LC_CTYPE):" << locale;
+
+    m_composeTable = xkb_compose_table_new_from_locale(m_XkbContext, locale, XKB_COMPOSE_COMPILE_NO_FLAGS);
+    if (m_composeTable)
+        m_composeState = xkb_compose_state_new(m_composeTable, XKB_COMPOSE_STATE_NO_FLAGS);
+
+    if (!m_composeTable) {
+        qCWarning(qLcQpaInputMethods, "failed to create compose table");
+        return;
+    }
+    if (!m_composeState) {
+        qCWarning(qLcQpaInputMethods, "failed to create compose state");
+        return;
+    }
+}
+
+bool QWaylandInputContext::filterEvent(const QEvent *event)
+{
+    auto keyEvent = static_cast<const QKeyEvent *>(event);
+    if (keyEvent->type() != QEvent::KeyPress)
+        return false;
+
+    if (!inputMethodAccepted())
+        return false;
+
+    // lazy initialization - we don't want to do this on an app startup
+    ensureInitialized();
+
+    if (!m_composeTable || !m_composeState)
+        return false;
+
+    xkb_compose_state_feed(m_composeState, keyEvent->nativeVirtualKey());
+
+    switch (xkb_compose_state_get_status(m_composeState)) {
+    case XKB_COMPOSE_COMPOSING:
+        return true;
+    case XKB_COMPOSE_CANCELLED:
+        reset();
+        return false;
+    case XKB_COMPOSE_COMPOSED:
+    {
+        const int size = xkb_compose_state_get_utf8(m_composeState, nullptr, 0);
+        QVarLengthArray<char, 32> buffer(size + 1);
+        xkb_compose_state_get_utf8(m_composeState, buffer.data(), buffer.size());
+        QString composedText = QString::fromUtf8(buffer.constData());
+
+        QInputMethodEvent event;
+        event.setCommitString(composedText);
+
+        if (!m_focusObject && qApp)
+            m_focusObject = qApp->focusObject();
+
+        if (m_focusObject)
+            QCoreApplication::sendEvent(m_focusObject, &event);
+        else
+            qCWarning(qLcQpaInputMethods, "no focus object");
+
+        reset();
+        return true;
+    }
+    case XKB_COMPOSE_NOTHING:
+        return false;
+    default:
+        Q_UNREACHABLE();
+        return false;
+    }
+}
+
+#endif
+
 }
 
 QT_END_NAMESPACE
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