Replace QTextDocumentResourceProvider with a std::function

376e3bd added the new class for Qt 6.1,
but during header review we concluded that using a class introduces
complexity wrt instance ownership and API design that can be avoided by
using a std::function instead.

The functionality is tied to QTextDocument, so the type definition and
the default provider API is added there.

Since std::function is not trivially copyable, the atomicity of the
previous implementation is not maintained, and concurrent modifications
of and access to the global default provider from multiple threads is
not allowed. The relevant use case can be supported by implementing a
resource provider that is thread safe.

Task-number: QTBUG-90211
Fixes: QTBUG-92208
Change-Id: I39215c5e51c7bd27f1dd29e1d9d908aecf754fb7
Reviewed-by: Kai Koehne <[email protected]>
(cherry picked from commit ccf1a1a)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

src/gui/CMakeLists.txt

@@ -242,7 +242,6 @@ qt_internal_add_module(Gui
         text/qtextobject.cpp text/qtextobject.h text/qtextobject_p.h
         text/qtextoption.cpp text/qtextoption.h
         text/qtexttable.cpp text/qtexttable.h text/qtexttable_p.h
-        text/qtextdocumentresourceprovider.cpp text/qtextdocumentresourceprovider.h
         util/qabstractlayoutstyleinfo.cpp util/qabstractlayoutstyleinfo_p.h
         util/qastchandler.cpp util/qastchandler_p.h
         util/qdesktopservices.cpp util/qdesktopservices.h

src/gui/text/qtextdocument.cpp

@@ -46,7 +46,6 @@
 #include "qtextdocumentfragment_p.h"
 #include "qtexttable.h"
 #include "qtextlist.h"
-#include "qtextdocumentresourceprovider.h"
 #include <qdebug.h>
 #if QT_CONFIG(regularexpression)
 #include <qregularexpression.h>
@@ -81,6 +80,9 @@ QT_BEGIN_NAMESPACE
 
 Q_CORE_EXPORT Q_DECL_CONST_FUNCTION unsigned int qt_int_sqrt(unsigned int n);
 
+namespace {
+    QTextDocument::ResourceProvider qt_defaultResourceProvider;
+};
 
 /*!
     Returns \c true if the string \a text is likely to be rich text;
@@ -2080,7 +2082,11 @@ void QTextDocument::print(QPagedPaintDevice *printer) const
     the resource. loadResource should then use addResource to add the
     resource to the cache.
 
-    \sa QTextDocument::ResourceType
+    If loadResource does not load the resource, then the resourceProvider and
+    lastly the defaultResourceProvider will be called, if set. Note that the
+    result from the provider will not be added automatically to the cache.
+
+    \sa QTextDocument::ResourceType, resourceProvider()
 */
 QVariant QTextDocument::resource(int type, const QUrl &name) const
 {
@@ -2093,9 +2099,9 @@ QVariant QTextDocument::resource(int type, const QUrl &name) const
             r = const_cast<QTextDocument *>(this)->loadResource(type, url);
             if (!r.isValid()) {
                 if (d->resourceProvider)
-                    r = d->resourceProvider->resource(url);
-                else if (auto defaultProvider = QTextDocumentResourceProvider::defaultProvider())
-                    r = defaultProvider->resource(url);
+                    r = d->resourceProvider(url);
+                else if (auto defaultProvider = defaultResourceProvider())
+                    r = defaultProvider(url);
             }
         }
     }
@@ -2131,26 +2137,62 @@ void QTextDocument::addResource(int type, const QUrl &name, const QVariant &reso
     \since 6.1
 
     Returns the resource provider for this text document.
+
+    \sa setResourceProvider(), defaultResourceProvider(), loadResource()
 */
-QTextDocumentResourceProvider *QTextDocument::resourceProvider() const
+QTextDocument::ResourceProvider QTextDocument::resourceProvider() const
 {
     Q_D(const QTextDocument);
     return d->resourceProvider;
 }
 
+/*!
+   \since 6.1
+   \typealias QTextDocument::ResourceProvider
+
+   Type alias for std::function\<QVariant(const QUrl&)\>.
+*/
+
 /*!
     \since 6.1
 
-    Sets the \a provider of resources for the text document.
+    Sets the provider of resources for the text document to \a provider.
 
-    \note The text document \e{does not} take ownership of the \a provider.
+    \sa resourceProvider(), loadResource()
 */
-void QTextDocument::setResourceProvider(QTextDocumentResourceProvider *provider)
+void QTextDocument::setResourceProvider(const ResourceProvider &provider)
 {
     Q_D(QTextDocument);
     d->resourceProvider = provider;
 }
 
+/*!
+    \since 6.1
+
+    Sets the default resource provider to \a provider.
+
+    The default provider will be used by all QTextDocuments that don't have an
+    explicit provider set.
+
+    \sa setResourceProvider(), loadResource()
+*/
+void QTextDocument::setDefaultResourceProvider(const ResourceProvider &provider)
+{
+    qt_defaultResourceProvider = provider;
+}
+
+/*!
+    \since 6.1
+
+    Returns the default resource provider.
+
+    \sa resourceProvider(), loadResource()
+*/
+QTextDocument::ResourceProvider QTextDocument::defaultResourceProvider()
+{
+    return qt_defaultResourceProvider;
+}
+
 /*!
     Loads data of the specified \a type from the resource with the
     given \a name.
@@ -2168,7 +2210,7 @@ void QTextDocument::setResourceProvider(QTextDocumentResourceProvider *provider)
     or a QTextDocument itself then the default implementation tries
     to retrieve the data from the parent.
 
-    \sa QTextDocumentResourceProvider
+    \sa QTextDocument::ResourceProvider
 */
 QVariant QTextDocument::loadResource(int type, const QUrl &name)
 {

src/gui/text/qtextdocument.h

@@ -68,8 +68,6 @@ class QVariant;
 class QRectF;
 class QTextOption;
 class QTextCursor;
-class QTextDocumentResourceProvider;
-
 
 namespace Qt
 {
@@ -240,8 +238,13 @@ class Q_GUI_EXPORT QTextDocument : public QObject
     QVariant resource(int type, const QUrl &name) const;
     void addResource(int type, const QUrl &name, const QVariant &resource);
 
-    QTextDocumentResourceProvider *resourceProvider() const;
-    void setResourceProvider(QTextDocumentResourceProvider *provider);
+    using ResourceProvider = std::function<QVariant(const QUrl&)>;
+
+    QTextDocument::ResourceProvider resourceProvider() const;
+    void setResourceProvider(const ResourceProvider &provider);
+
+    static QTextDocument::ResourceProvider defaultResourceProvider();
+    static void setDefaultResourceProvider(const ResourceProvider &provider);
 
     QList<QTextFormat> allFormats() const;
 

src/gui/text/qtextdocument_p.cpp

@@ -52,7 +52,6 @@
 #include "qtextdocumentlayout_p.h"
 #include "qtexttable.h"
 #include "qtextengine_p.h"
-#include "qtextdocumentresourceprovider.h"
 
 #include <stdlib.h>
 

src/gui/text/qtextdocument_p.h

@@ -366,7 +366,7 @@ class Q_GUI_EXPORT QTextDocumentPrivate : public QObjectPrivate
     QMap<int, QTextObject *> objects;
     QMap<QUrl, QVariant> resources;
     QMap<QUrl, QVariant> cachedResources;
-    QTextDocumentResourceProvider *resourceProvider;
+    QTextDocument::ResourceProvider resourceProvider;
     QString defaultStyleSheet;
 
     int lastBlockCount;

src/widgets/widgets/qlabel.cpp

@@ -1429,7 +1429,7 @@ void QLabel::setTextFormat(Qt::TextFormat format)
 
     Returns the resource provider for rich text of this label.
 */
-QTextDocumentResourceProvider *QLabel::resourceProvider() const
+QTextDocument::ResourceProvider QLabel::resourceProvider() const
 {
     Q_D(const QLabel);
     return d->control ? d->control->document()->resourceProvider() : d->resourceProvider;
@@ -1442,7 +1442,7 @@ QTextDocumentResourceProvider *QLabel::resourceProvider() const
 
     \note The label \e{does not} take ownership of the \a provider.
 */
-void QLabel::setResourceProvider(QTextDocumentResourceProvider *provider)
+void QLabel::setResourceProvider(const QTextDocument::ResourceProvider &provider)
 {
     Q_D(QLabel);
     d->resourceProvider = provider;

src/widgets/widgets/qlabel.h

@@ -43,13 +43,13 @@
 #include <QtWidgets/qtwidgetsglobal.h>
 #include <QtWidgets/qframe.h>
 #include <QtGui/qpicture.h>
+#include <QtGui/qtextdocument.h>
 
 QT_REQUIRE_CONFIG(label);
 
 QT_BEGIN_NAMESPACE
 
 
-class QTextDocumentResourceProvider;
 class QLabelPrivate;
 
 class Q_WIDGETS_EXPORT QLabel : public QFrame
@@ -93,8 +93,8 @@ class Q_WIDGETS_EXPORT QLabel : public QFrame
     Qt::TextFormat textFormat() const;
     void setTextFormat(Qt::TextFormat);
 
-    QTextDocumentResourceProvider *resourceProvider() const;
-    void setResourceProvider(QTextDocumentResourceProvider *provider);
+    QTextDocument::ResourceProvider resourceProvider() const;
+    void setResourceProvider(const QTextDocument::ResourceProvider &provider);
 
     Qt::Alignment alignment() const;
     void setAlignment(Qt::Alignment);

src/widgets/widgets/qlabel_p.h

@@ -154,7 +154,7 @@ class Q_AUTOTEST_EXPORT QLabelPrivate : public QFramePrivate
 #endif
     uint openExternalLinks : 1;
     // <-- space for more bit field values here
-    QTextDocumentResourceProvider *resourceProvider;
+    QTextDocument::ResourceProvider resourceProvider;
 
     friend class QMessageBoxPrivate;
 };