Message attached property

Create Message attached property to propagate parameters like room, timeline, index and maxContentWidth down to the message content avoiding lots of boilerplate

src/messageattached.cpp

@@ -0,0 +1,126 @@
+// SPDX-FileCopyrightText: 2025 James Graham <james.h.graham@protonmail.com>
+// SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+
+#include "messageattached.h"
+
+MessageAttached::MessageAttached(QObject *parent)
+    : QQuickAttachedPropertyPropagator(parent)
+{
+    if (parent == nullptr) {
+        qWarning() << "Message must be attached to an Item" << parent;
+        return;
+    }
+    initialize();
+}
+
+MessageAttached *MessageAttached::qmlAttachedProperties(QObject *object)
+{
+    return new MessageAttached(object);
+}
+
+NeoChatRoom *MessageAttached::room() const
+{
+    return m_room;
+}
+
+void MessageAttached::setRoom(NeoChatRoom *room)
+{
+    m_explicitRoom = true;
+    if (m_room == room) {
+        return;
+    }
+    m_room = room;
+    propagateMessage(this);
+    Q_EMIT roomChanged();
+}
+
+QQuickItem *MessageAttached::timeline() const
+{
+    return m_timeline;
+}
+
+void MessageAttached::setTimeline(QQuickItem *timeline)
+{
+    m_explicitTimeline = true;
+    if (m_timeline == timeline) {
+        return;
+    }
+    m_timeline = timeline;
+    propagateMessage(this);
+    Q_EMIT timelineChanged();
+}
+
+int MessageAttached::index() const
+{
+    return m_index;
+}
+
+void MessageAttached::setIndex(int index)
+{
+    m_explicitIndex = true;
+    if (m_index == index) {
+        return;
+    }
+    m_index = index;
+    propagateMessage(this);
+    Q_EMIT indexChanged();
+}
+
+qreal MessageAttached::maxContentWidth() const
+{
+    return m_maxContentWidth;
+}
+
+void MessageAttached::setMaxContentWidth(qreal maxContentWidth)
+{
+    m_explicitMaxContentWidth = true;
+    if (m_maxContentWidth == maxContentWidth) {
+        return;
+    }
+    m_maxContentWidth = maxContentWidth;
+    propagateMessage(this);
+    Q_EMIT maxContentWidthChanged();
+}
+
+void MessageAttached::propagateMessage(MessageAttached *message)
+{
+    if (m_explicitRoom || m_room != message->room()) {
+        m_room = message->room();
+        Q_EMIT roomChanged();
+    }
+
+    if (m_explicitTimeline || m_timeline != message->timeline()) {
+        m_timeline = message->timeline();
+        Q_EMIT timelineChanged();
+    }
+
+    if (m_explicitIndex || m_index != message->index()) {
+        m_index = message->index();
+        Q_EMIT indexChanged();
+    }
+
+    if (m_explicitMaxContentWidth || m_maxContentWidth != message->maxContentWidth()) {
+        m_maxContentWidth = message->maxContentWidth();
+        Q_EMIT maxContentWidthChanged();
+    }
+
+    const auto styles = attachedChildren();
+    for (auto *child : attachedChildren()) {
+        MessageAttached *message = qobject_cast<MessageAttached *>(child);
+        if (message != nullptr) {
+            message->propagateMessage(this);
+        }
+    }
+}
+
+void MessageAttached::attachedParentChange(QQuickAttachedPropertyPropagator *newParent, QQuickAttachedPropertyPropagator *oldParent)
+{
+    Q_UNUSED(oldParent);
+
+    MessageAttached *attachedParent = qobject_cast<MessageAttached *>(newParent);
+    if (attachedParent) {
+        propagateMessage(attachedParent);
+    }
+}
+
+#include "moc_messageattached.cpp"