Add load/save functionality to QQuickTextDocument (Tech Preview)

Since QTBUG-92155 is not done, we need an easy way to load and save text
into and out of a QTextDocument in QML. This patch follows the pattern
from Image and other types: add a `source` property, a URL from which
the file is to be loaded.

When it comes to saving, the pattern is not set: so far the only file
writing that has been available from QML is ItemGrabResult.saveToFile().
Since we need to save in specific formats, it makes sense to continue
that pattern: the text document knows how to do its own serialization,
so this is not suitable for generic data file I/O, even if we did have a
QML API for that. We add invokable functions save() and saveAs() for the
usual use cases in word processors and such. The URL extension
determines the file format.

Setting QQuickTextDocument's source is not allowed if the document has
unsaved changes. The user (app author) needs to call save() or override
modified to false first.

[ChangeLog][QtQuick][TextEdit] TextEdit.textDocument now has a source
property for loading files; save() and saveAs() functions for writing;
a modified property which tracks QTextDocument::modified; and an error
signal in case any of these operations fail. Setting the source
property is allowed only if the document is in unmodified state.
This API is in Tech Preview.

[ChangeLog][Controls][TextArea] TextArea.textDocument now has a source
property for loading files; save() and saveAs() functions for writing;
a modified property which tracks QTextDocument::modified; and an error
signal in case any of these operations fail. Setting the source
property is allowed only if the document is in unmodified state.
This API is in Tech Preview.

Change-Id: I687318523c7a520e02244e47224d067da55318b5
Reviewed-by: Axel Spoerl <[email protected]>

1 files changed, 231 insertions, 3 deletions

diff --git a/src/quick/items/qquicktextdocument.cpp b/src/quick/items/qquicktextdocument.cpp
index 81298596b0..432a69b494 100644
--- a/src/quick/items/qquicktextdocument.cpp
+++ b/src/quick/items/qquicktextdocument.cpp
@@ -12,10 +12,33 @@
 #include <QtQml/qqmlcontext.h>
 #include <QtQuick/private/qquickpixmap_p.h>
 
+#include <QtCore/qmimedatabase.h>
 #include <QtCore/qpointer.h>
 
 QT_BEGIN_NAMESPACE
 
+using namespace Qt::StringLiterals;
+
+/*!
+    \qmltype TextDocument
+    \instantiates QQuickTextDocument
+    \inqmlmodule QtQuick
+    \brief A wrapper around TextEdit's backing QTextDocument.
+
+    To load text into the document, set the \l source property. If the user then
+    modifies the text and wants to save the same document, call \l save() to save
+    it to the same source again (only if \l {QUrl::isLocalFile()}{it's a local file}).
+    Or call \l saveAs() to save it to a different file.
+
+    This class cannot be instantiated in QML, but is available from \l TextEdit::textDocument.
+
+    \note All loading and saving is done synchronously for now.
+    This may block the UI if the \l source is a slow network drive.
+    This may be improved in future versions of Qt.
+
+    \note This API is considered tech preview and may change in future versions of Qt.
+*/
+
 /*!
     \class QQuickTextDocument
     \since 5.1
@@ -27,8 +50,6 @@ QT_BEGIN_NAMESPACE
     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}.
-
-    This class cannot be instantiated in QML, but is available from \l TextEdit::textDocument.
 */
 
 /*!
@@ -42,6 +63,146 @@ QQuickTextDocument::QQuickTextDocument(QQuickItem *parent)
     Q_ASSERT(parent);
     d->editor = qobject_cast<QQuickTextEdit *>(parent);
     Q_ASSERT(d->editor);
+    connect(textDocument(), &QTextDocument::modificationChanged,
+            this, &QQuickTextDocument::modifiedChanged);
+}
+
+/*!
+    \qmlproperty url QtQuick::TextDocument::source
+    \since 6.7
+
+    QQuickTextDocument can handle any text format supported by Qt, loaded from
+    any URL scheme supported by Qt.
+
+    The URL may be absolute, or relative to the URL of the component.
+
+    The \c source property cannot be changed while the document's \l modified
+    state is \c true. If the user has modified the document contents, you
+    should prompt the user whether to \l save(), or else discard changes by
+    setting \c {modified = false} before setting the \l source property to a
+    different URL.
+
+    \sa QTextDocumentWriter::supportedDocumentFormats()
+*/
+QUrl QQuickTextDocument::source() const
+{
+    Q_D(const QQuickTextDocument);
+    return d->url;
+}
+
+void QQuickTextDocument::setSource(const QUrl &url)
+{
+    Q_D(QQuickTextDocument);
+
+    if (url == d->url)
+        return;
+
+    if (isModified()) {
+        qmlWarning(this) << "Existing document modified: you should save(),"
+                            "or call TextEdit.clear() before setting a different source";
+        return;
+    }
+
+    d->url = url;
+    emit sourceChanged();
+    d->load();
+}
+
+/*!
+    \qmlproperty bool QtQuick::TextDocument::modified
+    \since 6.7
+
+    This property holds whether the document has been modified by the user
+    since the last time it was loaded or saved. By default, this property is
+    \c false.
+
+    As with \l QTextDocument::modified, you can set the modified property:
+    for example, set it to \c false to allow setting the \c source property
+    to a different URL (thus discarding the user's changes).
+
+    \sa QTextDocument::modified
+*/
+bool QQuickTextDocument::isModified() const
+{
+    const auto *doc = textDocument();
+    return doc && doc->isModified();
+}
+
+void QQuickTextDocument::setModified(bool modified)
+{
+    if (auto *doc = textDocument())
+        doc->setModified(modified);
+}
+
+void QQuickTextDocumentPrivate::load()
+{
+    Q_Q(QQuickTextDocument);
+    const QString fileName = QQmlFile::urlToLocalFileOrQrc(url);
+    if (QFile::exists(fileName)) {
+        mimeType = QMimeDatabase().mimeTypeForFile(fileName);
+        QFile file(fileName);
+        if (file.open(QFile::ReadOnly)) {
+            QByteArray data = file.readAll();
+            if (auto *doc = editor->document()) {
+                doc->setBaseUrl(url.adjusted(QUrl::RemoveFilename));
+                if (mimeType.inherits("text/markdown"_L1)) {
+                    doc->setMarkdown(QString::fromUtf8(data));
+                } else if (mimeType.inherits("text/html"_L1)) {
+                    // If a user loads an HTML file, remember the encoding.
+                    // If the user then calls save() later, the same encoding will be used.
+                    encoding = QStringConverter::encodingForHtml(data);
+                    if (encoding) {
+                        QStringDecoder decoder(*encoding);
+                        doc->setHtml(decoder(data));
+                    } else {
+                        // fall back to utf8
+                        doc->setHtml(QString::fromUtf8(data));
+                    }
+                } else {
+                    doc->setPlainText(QString::fromUtf8(data));
+                }
+                doc->setModified(false);
+            }
+        } else {
+            emit q->error(QQuickTextDocument::tr("Cannot load: ") + file.errorString());
+        }
+    }
+}
+
+void QQuickTextDocumentPrivate::writeTo(const QUrl &fileUrl)
+{
+    Q_Q(QQuickTextDocument);
+    auto *doc = editor->document();
+    if (!doc)
+        return;
+
+    const QString filePath = fileUrl.toLocalFile();
+    const bool sameUrl = fileUrl == url;
+    const auto type = (sameUrl ? mimeType : QMimeDatabase().mimeTypeForUrl(fileUrl));
+    const bool isHtml = type.inherits("text/html"_L1);
+    QFile file(filePath);
+    if (!file.open(QFile::WriteOnly | QFile::Truncate | (isHtml ? QFile::NotOpen : QFile::Text))) {
+        emit q->error(QQuickTextDocument::tr("Cannot save: ") + file.errorString());
+        return;
+    }
+    QByteArray raw;
+    if (type.inherits("text/markdown"_L1)) {
+        raw = doc->toMarkdown().toUtf8();
+    } else if (isHtml) {
+        if (sameUrl && encoding) {
+            QStringEncoder enc(*encoding);
+            raw = enc.encode(doc->toHtml());
+        } else {
+            // default to UTF-8 unless the user is saving the same file as previously loaded
+            raw = doc->toHtml().toUtf8();
+        }
+    } else {
+        raw = doc->toPlainText().toUtf8();
+    }
+
+    file.write(raw);
+    file.close();
+    doc->setModified(false);
 }
 
 QTextDocument *QQuickTextDocumentPrivate::document() const
@@ -52,9 +213,16 @@ QTextDocument *QQuickTextDocumentPrivate::document() const
 void QQuickTextDocumentPrivate::setDocument(QTextDocument *doc)
 {
     Q_Q(QQuickTextDocument);
-    if (doc == editor->document())
+    QTextDocument *oldDoc = editor->document();
+    if (doc == oldDoc)
         return;
 
+    if (oldDoc)
+        oldDoc->disconnect(q);
+    if (doc) {
+        q->connect(doc, &QTextDocument::modificationChanged,
+                   q, &QQuickTextDocument::modifiedChanged);
+    }
     editor->setDocument(doc);
     emit q->textDocumentChanged();
 }
@@ -79,6 +247,59 @@ void QQuickTextDocument::setTextDocument(QTextDocument *document)
     d_func()->setDocument(document);
 }
 
+/*!
+    \fn void QQuickTextDocument::textDocumentChanged()
+    \since 6.7
+
+    This signal is emitted when the underlying QTextDocument is
+    replaced with a different instance.
+
+    \sa setTextDocument()
+*/
+
+/*!
+    \qmlmethod void QtQuick::TextDocument::save()
+    \brief Saves the contents to the same file and format specified by \l source.
+    \since 6.7
+
+    \note You can save only to a \l {QUrl::isLocalFile()}{file on a mounted filesystem}.
+
+    \sa source, saveAs()
+*/
+void QQuickTextDocument::save()
+{
+    Q_D(QQuickTextDocument);
+    d->writeTo(d->url);
+}
+
+/*!
+    \qmlmethod void QtQuick::TextDocument::saveAs(url url)
+    \brief Saves the contents to the file and format specified by \a url.
+    \since 6.7
+
+    The file extension in \a url specifies the file format
+    (as determined by QMimeDatabase::mimeTypeForUrl()).
+
+    \note You can save only to a \l {QUrl::isLocalFile()}{file on a mounted filesystem}.
+
+    \sa source, saveAs()
+*/
+void QQuickTextDocument::saveAs(const QUrl &url)
+{
+    Q_D(QQuickTextDocument);
+    if (!url.isLocalFile()) {
+        emit error(tr("Can only save to local files"));
+        return;
+    }
+    d->writeTo(url);
+
+    if (url == d->url)
+        return;
+
+    d->url = url;
+    emit sourceChanged();
+}
+
 QQuickTextImageHandler::QQuickTextImageHandler(QObject *parent)
     : QObject(parent)
 {
@@ -125,6 +346,13 @@ QSizeF QQuickTextImageHandler::intrinsicSize(
     return QSizeF();
 }
 
+/*!
+    \qmlsignal QtQuick::TextDocument::error(string message)
+
+    This signal is emitted when an error \a message (translated string) should
+    be presented to the user, for example with a MessageDialog.
+*/
+
 QT_END_NAMESPACE
 
 #include "moc_qquicktextdocument.cpp"