Defer construction of TextEdit/TextInput delegates.

Don't create instances of the delegate components until the item
gains focus, or the cursorVisible property is set to true.

Cursor delegates are typically small and relatively fast to create and
so won't have a significant cost during a one off focus in event,
but that cost can still add up when creating a number of TextInputs
or TextEdits at once.  If a delegate that is instantiated immeditately
is required it is possible to instead create a child item and bind to
the cursorRectangle and cursorVisible properties.

Change-Id: I5ec2b5b6a30e534aee3dd5a58c6a5ac0686f5ce2
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>

1 files changed, 126 insertions, 0 deletions

diff --git a/src/quick/items/qquicktextutil_p.h b/src/quick/items/qquicktextutil_p.h
new file mode 100644
index 0000000000..91ef40b221
--- /dev/null
+++ b/src/quick/items/qquicktextutil_p.h
@@ -0,0 +1,126 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** GNU Lesser General Public License Usage
+** This file may be used under the terms of the GNU Lesser General Public
+** License version 2.1 as published by the Free Software Foundation and
+** appearing in the file LICENSE.LGPL included in the packaging of this
+** file. Please review the following information to ensure the GNU Lesser
+** General Public License version 2.1 requirements will be met:
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights. These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU General
+** Public License version 3.0 as published by the Free Software Foundation
+** and appearing in the file LICENSE.GPL included in the packaging of this
+** file. Please review the following information to ensure the GNU General
+** Public License version 3.0 requirements will be met:
+** http://www.gnu.org/copyleft/gpl.html.
+**
+** Other Usage
+** Alternatively, this file may be used in accordance with the terms and
+** conditions contained in a signed written agreement between you and Nokia.
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQUICKTEXTUTIL_P_H
+#define QQUICKTEXTUTIL_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtQml/qqml.h>
+#include <QtQml/qqmlincubator.h>
+#include <QtQuick/qquickitem.h>
+
+QT_BEGIN_NAMESPACE
+
+class QQuickTextUtil : public QObject   // For the benefit of translations.
+{
+    Q_OBJECT
+public:
+    template <typename Private> static void setCursorDelegate(Private *d, QQmlComponent *delegate);
+    template <typename Private> static void createCursor(Private *d);
+
+private:
+    static QQuickItem *createCursor(
+            QQmlComponent *component,
+            QQuickItem *parent,
+            const QRectF &cursorRectangle,
+            const char *className);
+};
+
+template <typename Private>
+void QQuickTextUtil::setCursorDelegate(Private *d, QQmlComponent *delegate)
+{
+    if (d->cursorComponent == delegate)
+        return;
+
+    typename Private::Public *parent = d->q_func();
+
+    if (d->cursorComponent) {
+        disconnect(d->cursorComponent, SIGNAL(statusChanged(QQmlComponent::Status)),
+                parent, SLOT(createCursor()));
+    }
+
+    delete d->cursorItem;
+    d->cursorItem = 0;
+    d->cursorPending = true;
+
+    d->cursorComponent = delegate;
+
+    if (parent->isCursorVisible() && parent->isComponentComplete())
+        createCursor(d);
+
+    emit parent->cursorDelegateChanged();
+}
+
+template <typename Private>
+void QQuickTextUtil::createCursor(Private *d)
+{
+    if (!d->cursorPending)
+        return;
+
+    d->cursorPending = false;
+
+    typename Private::Public *parent = d->q_func();
+    if (d->cursorComponent) {
+        d->cursorItem = createCursor(
+                d->cursorComponent,
+                parent,
+                parent->cursorRectangle(),
+                Private::Public::staticMetaObject.className());
+    }
+
+    d->setNativeCursorEnabled(!d->cursorItem);
+    d->updateType = Private::UpdatePaintNode;
+    parent->update();
+}
+
+QT_END_NAMESPACE
+
+#endif