Add setter and notifier for QQuickTextDocument's document

Users want to be able to provide their own "special" instances of
QTextDocument, or custom subclasses. But so far we allow this only
from C++, not from QML.

QQuickTextDocument is created lazily in QQuickTextEdit::textDocument()
so it's not possible to rely on it to hold the actual QTextDocument all
the time. It's only a facade provided to the user. But QQuickTextEdit
holds the QTextDocument, and is the only class that creates
QQuickTextDocument, and sets the parent to itself; so QQuickTextDocument
can rely on accessing the TextEdit's document rather than maintaining
its own pointer.

textEdit.dot is basically a collaboration diagram showing which objects
creates which, the parents, and which objects get swapped out if the
user calls setTextDocument().

Task-number: QTBUG-35688
Change-Id: Iac5000aa8027a75a000d4501190f3ee5f04e426e
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 35 insertions, 12 deletions

diff --git a/src/quick/items/qquicktextdocument.cpp b/src/quick/items/qquicktextdocument.cpp
index 37a054f33a..81298596b0 100644
--- a/src/quick/items/qquicktextdocument.cpp
+++ b/src/quick/items/qquicktextdocument.cpp
@@ -23,15 +23,12 @@ QT_BEGIN_NAMESPACE
     \inmodule QtQuick
 
     This class provides access to the QTextDocument of QQuickTextEdit elements.
-    This is provided to allow usage of the \l{Rich Text Processing} functionalities of Qt.
-    You are not allowed to modify the document, but it can be used to output content, for example with \l{QTextDocumentWriter}),
-    or provide additional formatting, for example with \l{QSyntaxHighlighter}.
+    This is provided to allow usage of the \l{Rich Text Processing} functionalities of Qt,
+    including document modifications. It can also be used to output content,
+    for example with \l{QTextDocumentWriter}), or provide additional formatting,
+    for example with \l{QSyntaxHighlighter}.
 
-    The class has to be used from C++ directly, using the property of the \l TextEdit.
-
-    Warning: The QTextDocument provided is used internally by \l {Qt Quick} elements to provide text manipulation primitives.
-    You are not allowed to perform any modification of the internal state of the QTextDocument. If you do, the element
-    in question may stop functioning or crash.
+    This class cannot be instantiated in QML, but is available from \l TextEdit::textDocument.
 */
 
 /*!
@@ -43,17 +40,43 @@ QQuickTextDocument::QQuickTextDocument(QQuickItem *parent)
 {
     Q_D(QQuickTextDocument);
     Q_ASSERT(parent);
-    Q_ASSERT(qobject_cast<QQuickTextEdit*>(parent));
-    d->document = QPointer<QTextDocument>(qobject_cast<QQuickTextEdit*>(parent)->d_func()->document);
+    d->editor = qobject_cast<QQuickTextEdit *>(parent);
+    Q_ASSERT(d->editor);
+}
+
+QTextDocument *QQuickTextDocumentPrivate::document() const
+{
+    return editor->document();
+}
+
+void QQuickTextDocumentPrivate::setDocument(QTextDocument *doc)
+{
+    Q_Q(QQuickTextDocument);
+    if (doc == editor->document())
+        return;
+
+    editor->setDocument(doc);
+    emit q->textDocumentChanged();
 }
 
 /*!
    Returns a pointer to the QTextDocument object.
 */
-QTextDocument* QQuickTextDocument::textDocument() const
+QTextDocument *QQuickTextDocument::textDocument() const
 {
     Q_D(const QQuickTextDocument);
-    return d->document.data();
+    return d->document();
+}
+
+/*!
+    \brief Sets the given \a document.
+    \since 6.7
+
+    The caller retains ownership of the document.
+*/
+void QQuickTextDocument::setTextDocument(QTextDocument *document)
+{
+    d_func()->setDocument(document);
 }
 
 QQuickTextImageHandler::QQuickTextImageHandler(QObject *parent)