Allow attaching TextArea to a Flickable

It is not always possible to let TextArea grow infinitely, but in
some cases it should be scrollable on its own. Even though it is not
a built-in feature of TextArea like in Qt Quick Controls 1, this change
makes it straight-forward to attach TextArea to a Flickable. This makes
TextArea behave like a standalone scrollable editor.

Change-Id: I8181e8ebe0edbcdfef2c30c9e102db7cbe4ff705
Task-number: QTBUG-51677
Task-number: QTBUG-52169
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

10 files changed, 345 insertions, 7 deletions

diff --git a/src/imports/controls/doc/images/qtquickcontrols2-textarea-flickable.png b/src/imports/controls/doc/images/qtquickcontrols2-textarea-flickable.png
new file mode 100644
index 00000000..39578f71
--- /dev/null
+++ b/src/imports/controls/doc/images/qtquickcontrols2-textarea-flickable.png
diff --git a/src/imports/controls/doc/images/qtquickcontrols2-textarea.png b/src/imports/controls/doc/images/qtquickcontrols2-textarea.png
index f468bfd4..924f6681 100644
--- a/src/imports/controls/doc/images/qtquickcontrols2-textarea.png
+++ b/src/imports/controls/doc/images/qtquickcontrols2-textarea.png
diff --git a/src/imports/controls/doc/snippets/qtquickcontrols2-textarea-flickable.qml b/src/imports/controls/doc/snippets/qtquickcontrols2-textarea-flickable.qml
new file mode 100644
index 00000000..e11750cb
--- /dev/null
+++ b/src/imports/controls/doc/snippets/qtquickcontrols2-textarea-flickable.qml
@@ -0,0 +1,50 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Free Documentation License Usage
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of
+** this file. Please review the following information to ensure
+** the GNU Free Documentation License version 1.3 requirements
+** will be met: http://www.gnu.org/copyleft/fdl.html.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.0
+import QtQuick.Controls 2.0
+
+Item {
+    width: 100
+    height: 100
+
+    Binding { target: flickable.ScrollBar.vertical; property: "active"; value: true }
+
+    //! [1]
+    Flickable {
+        id: flickable
+        anchors.fill: parent
+
+        TextArea.flickable: TextArea {
+            text: "TextArea\n...\n...\n...\n...\n...\n...\n"
+            wrapMode: TextArea.Wrap
+        }
+
+        ScrollBar.vertical: ScrollBar { }
+    }
+    //! [1]
+}
diff --git a/src/imports/controls/doc/snippets/qtquickcontrols2-textarea.qml b/src/imports/controls/doc/snippets/qtquickcontrols2-textarea.qml
index 84994008..52077f90 100644
--- a/src/imports/controls/doc/snippets/qtquickcontrols2-textarea.qml
+++ b/src/imports/controls/doc/snippets/qtquickcontrols2-textarea.qml
@@ -29,5 +29,5 @@ import QtQuick 2.0
 import QtQuick.Controls 2.0
 
 TextArea {
-    text: "Text\nArea..."
+    placeholderText: qsTr("Enter description")
 }
diff --git a/src/imports/controls/material/TextArea.qml b/src/imports/controls/material/TextArea.qml
index aa9cb12f..8098ac42 100644
--- a/src/imports/controls/material/TextArea.qml
+++ b/src/imports/controls/material/TextArea.qml
@@ -56,6 +56,7 @@ T.TextArea {
     selectedTextColor: Material.primaryHighlightedTextColor
     cursorDelegate: Rectangle {
         id: cursor
+        clip: true // TODO
         color: control.Material.accentColor
         width: 2
         visible: control.activeFocus && control.selectionStart === control.selectionEnd
@@ -99,7 +100,7 @@ T.TextArea {
 
     //! [background]
     background: Rectangle {
-        y: control.height - height - control.bottomPadding / 2
+        y: parent.height - height - control.bottomPadding / 2
         implicitWidth: 120
         height: control.activeFocus ? 2 : 1
         color: control.activeFocus ? control.Material.accentColor : control.Material.hintTextColor
diff --git a/src/imports/templates/qtquicktemplates2plugin.cpp b/src/imports/templates/qtquicktemplates2plugin.cpp
index 86adf973..ab46c7ab 100644
--- a/src/imports/templates/qtquicktemplates2plugin.cpp
+++ b/src/imports/templates/qtquicktemplates2plugin.cpp
@@ -148,6 +148,7 @@ void QtQuickTemplates2Plugin::registerTypes(const char *uri)
     qmlRegisterType<QQuickSwitchDelegate>(uri, 2, 0, "SwitchDelegate");
     qmlRegisterType<QQuickTabBar>(uri, 2, 0, "TabBar");
     qmlRegisterType<QQuickTabButton>(uri, 2, 0, "TabButton");
+    qmlRegisterType<QQuickTextAreaAttached>();
     qmlRegisterType<QQuickTextArea>(uri, 2, 0, "TextArea");
     qmlRegisterType<QQuickTextField>(uri, 2, 0, "TextField");
     qmlRegisterType<QQuickToolBar>(uri, 2, 0, "ToolBar");
diff --git a/src/quicktemplates2/qquicktextarea.cpp b/src/quicktemplates2/qquicktextarea.cpp
index f7a281d7..92f5cf64 100644
--- a/src/quicktemplates2/qquicktextarea.cpp
+++ b/src/quicktemplates2/qquicktextarea.cpp
@@ -40,9 +40,11 @@
 #include "qquickcontrol_p_p.h"
 
 #include <QtGui/qguiapplication.h>
+#include <QtQml/qqmlinfo.h>
 #include <QtQuick/private/qquickitem_p.h>
 #include <QtQuick/private/qquicktext_p.h>
 #include <QtQuick/private/qquickclipnode_p.h>
+#include <QtQuick/private/qquickflickable_p.h>
 
 #ifndef QT_NO_ACCESSIBILITY
 #include <QtQuick/private/qquickaccessibleattached_p.h>
@@ -61,12 +63,37 @@ QT_BEGIN_NAMESPACE
     TextArea is a multi-line text editor. TextArea extends TextEdit with
     a \l {placeholderText}{placeholder text} functionality, and adds decoration.
 
+    \image qtquickcontrols2-textarea.png
+
     \code
     TextArea {
         placeholderText: qsTr("Enter description")
     }
     \endcode
 
+    TextArea is not scrollable by itself. Especially on screen-size constrained
+    platforms, it is often preferable to make entire application pages scrollable.
+    On such a scrollable page, a non-scrollable TextArea might behave better than
+    nested scrollable controls. Notice, however, that in such a scenario, the background
+    decoration of the TextArea scrolls together with the rest of the scrollable
+    content.
+
+    If you want to make a TextArea scrollable, for example, when it covers
+    an entire application page, attach it to a \l Flickable and combine with a
+    \l ScrollBar or \l ScrollIndicator.
+
+    \image qtquickcontrols2-textarea-flickable.png
+
+    \snippet qtquickcontrols2-textarea-flickable.qml 1
+
+    A TextArea that is attached to a Flickable does the following:
+
+    \list
+    \li Sets the content size automatically
+    \li Ensures that the background decoration stays in place
+    \li Clips the content
+    \endlist
+
     \sa TextField, {Customizing TextArea}, {Input Controls}
 */
 
@@ -79,7 +106,7 @@ QT_BEGIN_NAMESPACE
 */
 
 QQuickTextAreaPrivate::QQuickTextAreaPrivate()
-    : background(nullptr), focusReason(Qt::OtherFocusReason), accessibleAttached(nullptr)
+    : background(nullptr), focusReason(Qt::OtherFocusReason), accessibleAttached(nullptr), flickable(nullptr)
 {
 #ifndef QT_NO_ACCESSIBILITY
     QAccessible::installActivationObserver(this);
@@ -99,16 +126,133 @@ void QQuickTextAreaPrivate::resizeBackground()
     if (background) {
         QQuickItemPrivate *p = QQuickItemPrivate::get(background);
         if (!p->widthValid && qFuzzyIsNull(background->x())) {
-            background->setWidth(q->width());
+            if (flickable)
+                background->setWidth(flickable->width());
+            else
+                background->setWidth(q->width());
             p->widthValid = false;
         }
         if (!p->heightValid && qFuzzyIsNull(background->y())) {
-            background->setHeight(q->height());
+            if (flickable)
+                background->setHeight(flickable->height());
+            else
+                background->setHeight(q->height());
             p->heightValid = false;
         }
     }
 }
 
+void QQuickTextAreaPrivate::attachFlickable(QQuickFlickable *item)
+{
+    Q_Q(QQuickTextArea);
+    flickable = item;
+    q->setParentItem(flickable->contentItem());
+
+    if (background)
+        background->setParentItem(flickable);
+
+    QObjectPrivate::connect(q, &QQuickTextArea::contentSizeChanged, this, &QQuickTextAreaPrivate::resizeFlickableContent);
+    QObjectPrivate::connect(q, &QQuickTextEdit::cursorRectangleChanged, this, &QQuickTextAreaPrivate::ensureCursorVisible);
+
+    QObject::connect(flickable, &QQuickFlickable::contentXChanged, q, &QQuickItem::update);
+    QObject::connect(flickable, &QQuickFlickable::contentYChanged, q, &QQuickItem::update);
+
+    QQuickItemPrivate::get(flickable)->updateOrAddGeometryChangeListener(this, QQuickItemPrivate::SizeChange);
+    QObjectPrivate::connect(flickable, &QQuickFlickable::contentWidthChanged, this, &QQuickTextAreaPrivate::resizeFlickableControl);
+    QObjectPrivate::connect(flickable, &QQuickFlickable::contentHeightChanged, this, &QQuickTextAreaPrivate::resizeFlickableControl);
+
+    resizeFlickableControl();
+}
+
+void QQuickTextAreaPrivate::detachFlickable()
+{
+    Q_Q(QQuickTextArea);
+    q->setParentItem(nullptr);
+    if (background && background->parentItem() == flickable)
+        background->setParentItem(q);
+
+    QObjectPrivate::disconnect(q, &QQuickTextArea::contentSizeChanged, this, &QQuickTextAreaPrivate::resizeFlickableContent);
+    QObjectPrivate::disconnect(q, &QQuickTextEdit::cursorRectangleChanged, this, &QQuickTextAreaPrivate::ensureCursorVisible);
+
+    QObject::disconnect(flickable, &QQuickFlickable::contentXChanged, q, &QQuickItem::update);
+    QObject::disconnect(flickable, &QQuickFlickable::contentYChanged, q, &QQuickItem::update);
+
+    QQuickItemPrivate::get(flickable)->updateOrRemoveGeometryChangeListener(this, QQuickItemPrivate::SizeChange);
+    QObjectPrivate::disconnect(flickable, &QQuickFlickable::contentWidthChanged, this, &QQuickTextAreaPrivate::resizeFlickableControl);
+    QObjectPrivate::disconnect(flickable, &QQuickFlickable::contentHeightChanged, this, &QQuickTextAreaPrivate::resizeFlickableControl);
+
+    flickable = nullptr;
+}
+
+void QQuickTextAreaPrivate::ensureCursorVisible()
+{
+    Q_Q(QQuickTextArea);
+    if (!flickable)
+        return;
+
+    const qreal cx = flickable->contentX();
+    const qreal cy = flickable->contentY();
+    const qreal w = flickable->width();
+    const qreal h = flickable->height();
+
+    const qreal tp = q->topPadding();
+    const qreal lp = q->leftPadding();
+    const QRectF cr = q->cursorRectangle();
+
+    if (cr.left() <= cx + lp) {
+        flickable->setContentX(cr.left() - lp);
+    } else {
+        // calculate the rectangle of the next character and ensure that
+        // it's visible if it's on the same line with the cursor
+        const qreal rp = q->rightPadding();
+        const QRectF nr = q->cursorPosition() < q->length() ? q->positionToRectangle(q->cursorPosition() + 1) : QRectF();
+        if (qFuzzyCompare(nr.y(), cr.y()) && nr.right() >= cx + lp + w - rp)
+            flickable->setContentX(nr.right() - w + rp);
+        else if (cr.right() >= cx + lp + w - rp)
+            flickable->setContentX(cr.right() - w + rp);
+    }
+
+    if (cr.top() <= cy + tp) {
+        flickable->setContentY(cr.top() - tp);
+    } else {
+        const qreal bp = q->bottomPadding();
+        if (cr.bottom() >= cy + tp + h - bp)
+            flickable->setContentY(cr.bottom() - h + bp);
+    }
+}
+
+void QQuickTextAreaPrivate::resizeFlickableControl()
+{
+    Q_Q(QQuickTextArea);
+    if (!flickable)
+        return;
+
+    const qreal w = wrapMode == QQuickTextArea::NoWrap ? qMax(flickable->width(), flickable->contentWidth()) : flickable->width();
+    const qreal h = qMax(flickable->height(), flickable->contentHeight());
+    q->setSize(QSizeF(w, h));
+
+    resizeBackground();
+}
+
+void QQuickTextAreaPrivate::resizeFlickableContent()
+{
+    Q_Q(QQuickTextArea);
+    if (!flickable)
+        return;
+
+    flickable->setContentWidth(q->contentWidth() + q->leftPadding() + q->rightPadding());
+    flickable->setContentHeight(q->contentHeight() + q->topPadding() + q->bottomPadding());
+}
+
+void QQuickTextAreaPrivate::itemGeometryChanged(QQuickItem *item, const QRectF &newGeometry, const QRectF &oldGeometry)
+{
+    Q_UNUSED(item);
+    Q_UNUSED(newGeometry);
+    Q_UNUSED(oldGeometry);
+
+    resizeFlickableControl();
+}
+
 qreal QQuickTextAreaPrivate::getImplicitWidth() const
 {
     return QQuickItemPrivate::getImplicitWidth();
@@ -148,6 +292,11 @@ QQuickTextArea::~QQuickTextArea()
 {
 }
 
+QQuickTextAreaAttached *QQuickTextArea::qmlAttachedProperties(QObject *object)
+{
+    return new QQuickTextAreaAttached(object);
+}
+
 /*!
     \internal
 
@@ -345,17 +494,29 @@ void QQuickTextArea::geometryChanged(const QRectF &newGeometry, const QRectF &ol
 
 QSGNode *QQuickTextArea::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *data)
 {
+    Q_D(QQuickTextArea);
     QQuickDefaultClipNode *clipNode = static_cast<QQuickDefaultClipNode *>(oldNode);
     if (!clipNode)
         clipNode = new QQuickDefaultClipNode(QRectF());
 
-    clipNode->setRect(clipRect().adjusted(leftPadding(), topPadding(), -rightPadding(), -bottomPadding()));
+    QQuickItem *clipper = this;
+    if (d->flickable)
+        clipper = d->flickable;
+
+    const QRectF cr = clipper->clipRect().adjusted(leftPadding(), topPadding(), -rightPadding(), -bottomPadding());
+    clipNode->setRect(!d->flickable ? cr : cr.translated(d->flickable->contentX(), d->flickable->contentY()));
     clipNode->update();
 
     QSGNode *textNode = QQuickTextEdit::updatePaintNode(clipNode->firstChild(), data);
     if (!textNode->parent())
         clipNode->appendChildNode(textNode);
 
+    if (d->cursorItem) {
+        QQuickDefaultClipNode *cursorNode = QQuickItemPrivate::get(d->cursorItem)->clipNode();
+        if (cursorNode)
+            cursorNode->setClipRect(d->cursorItem->mapRectFromItem(clipper, cr));
+    }
+
     return clipNode;
 }
 
@@ -420,4 +581,59 @@ void QQuickTextArea::timerEvent(QTimerEvent *event)
     }
 }
 
+class QQuickTextAreaAttachedPrivate : public QObjectPrivate
+{
+public:
+    QQuickTextAreaAttachedPrivate() : control(nullptr) { }
+
+    QQuickTextArea *control;
+};
+
+QQuickTextAreaAttached::QQuickTextAreaAttached(QObject *parent) :
+    QObject(*(new QQuickTextAreaAttachedPrivate), parent)
+{
+}
+
+QQuickTextAreaAttached::~QQuickTextAreaAttached()
+{
+}
+
+/*!
+    \qmlattachedproperty TextArea QtQuick.Controls::TextArea::flickable
+
+    This property attaches a text area to a \l Flickable.
+
+    \snippet qtquickcontrols2-textarea-flickable.qml 1
+
+    \sa ScrollBar, ScrollIndicator
+*/
+QQuickTextArea *QQuickTextAreaAttached::flickable() const
+{
+    Q_D(const QQuickTextAreaAttached);
+    return d->control;
+}
+
+void QQuickTextAreaAttached::setFlickable(QQuickTextArea *control)
+{
+    Q_D(QQuickTextAreaAttached);
+    QQuickFlickable *flickable = qobject_cast<QQuickFlickable *>(parent());
+    if (!flickable) {
+        qmlInfo(parent()) << "TextArea must be attached to a Flickable";
+        return;
+    }
+
+    if (d->control == control)
+        return;
+
+    if (d->control)
+        QQuickTextAreaPrivate::get(d->control)->detachFlickable();
+
+    d->control = control;
+
+    if (control)
+        QQuickTextAreaPrivate::get(control)->attachFlickable(flickable);
+
+    emit flickableChanged();
+}
+
 QT_END_NAMESPACE
diff --git a/src/quicktemplates2/qquicktextarea_p.h b/src/quicktemplates2/qquicktextarea_p.h
index c62d35df..7c145a9a 100644
--- a/src/quicktemplates2/qquicktextarea_p.h
+++ b/src/quicktemplates2/qquicktextarea_p.h
@@ -55,6 +55,7 @@ QT_BEGIN_NAMESPACE
 
 class QQuickText;
 class QQuickTextAreaPrivate;
+class QQuickTextAreaAttached;
 class QQuickMouseEvent;
 
 class Q_QUICKTEMPLATES2_EXPORT QQuickTextArea : public QQuickTextEdit
@@ -71,6 +72,8 @@ public:
     explicit QQuickTextArea(QQuickItem *parent = nullptr);
     ~QQuickTextArea();
 
+    static QQuickTextAreaAttached *qmlAttachedProperties(QObject *object);
+
     QFont font() const;
     void setFont(const QFont &font);
 
@@ -111,8 +114,31 @@ private:
     Q_DECLARE_PRIVATE(QQuickTextArea)
 };
 
+class QQuickTextAreaAttachedPrivate;
+
+class Q_QUICKTEMPLATES2_EXPORT QQuickTextAreaAttached : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(QQuickTextArea *flickable READ flickable WRITE setFlickable NOTIFY flickableChanged FINAL)
+
+public:
+    explicit QQuickTextAreaAttached(QObject *parent);
+    ~QQuickTextAreaAttached();
+
+    QQuickTextArea *flickable() const;
+    void setFlickable(QQuickTextArea *control);
+
+Q_SIGNALS:
+    void flickableChanged();
+
+private:
+    Q_DISABLE_COPY(QQuickTextAreaAttached)
+    Q_DECLARE_PRIVATE(QQuickTextAreaAttached)
+};
+
 QT_END_NAMESPACE
 
 QML_DECLARE_TYPE(QQuickTextArea)
+QML_DECLARE_TYPEINFO(QQuickTextArea, QML_HAS_ATTACHED_PROPERTIES)
 
 #endif // QQUICKTEXTAREA_P_H
diff --git a/src/quicktemplates2/qquicktextarea_p_p.h b/src/quicktemplates2/qquicktextarea_p_p.h
index 99ee7cdb..8af5d0d7 100644
--- a/src/quicktemplates2/qquicktextarea_p_p.h
+++ b/src/quicktemplates2/qquicktextarea_p_p.h
@@ -49,6 +49,7 @@
 //
 
 #include <QtQuick/private/qquicktextedit_p_p.h>
+#include <QtQuick/private/qquickitemchangelistener_p.h>
 #include <QtQuickTemplates2/private/qquickpresshandler_p_p.h>
 
 #include "qquicktextarea_p.h"
@@ -59,9 +60,10 @@
 
 QT_BEGIN_NAMESPACE
 
+class QQuickFlickable;
 class QQuickAccessibleAttached;
 
-class QQuickTextAreaPrivate : public QQuickTextEditPrivate
+class QQuickTextAreaPrivate : public QQuickTextEditPrivate, public QQuickItemChangeListener
 #ifndef QT_NO_ACCESSIBILITY
     , public QAccessible::ActivationObserver
 #endif
@@ -79,6 +81,14 @@ public:
     void resolveFont();
     void inheritFont(const QFont &f);
 
+    void attachFlickable(QQuickFlickable *flickable);
+    void detachFlickable();
+    void ensureCursorVisible();
+    void resizeFlickableControl();
+    void resizeFlickableContent();
+
+    void itemGeometryChanged(QQuickItem *item, const QRectF &newGeometry, const QRectF &oldGeometry) override;
+
     qreal getImplicitWidth() const override;
     qreal getImplicitHeight() const override;
 
@@ -98,6 +108,7 @@ public:
     Qt::FocusReason focusReason;
     QQuickPressHandler pressHandler;
     QQuickAccessibleAttached *accessibleAttached;
+    QQuickFlickable *flickable;
 };
 
 QT_END_NAMESPACE
diff --git a/tests/auto/controls/data/tst_textarea.qml b/tests/auto/controls/data/tst_textarea.qml
index 4e49c8fc..f09304b0 100644
--- a/tests/auto/controls/data/tst_textarea.qml
+++ b/tests/auto/controls/data/tst_textarea.qml
@@ -56,6 +56,15 @@ TestCase {
     }
 
     Component {
+        id: flickable
+        Flickable {
+            width: 200
+            height: 200
+            TextArea.flickable: TextArea { }
+        }
+    }
+
+    Component {
         id: signalSpy
         SignalSpy { }
     }
@@ -137,4 +146,28 @@ TestCase {
 
         control.destroy()
     }
+
+    function test_flickable() {
+        var control = flickable.createObject(testCase, {text:"line0"})
+        verify(control)
+
+        var textArea = control.TextArea.flickable
+        verify(textArea)
+
+        for (var i = 1; i <= 100; ++i)
+            textArea.text += "line\n" + i
+
+        verify(textArea.contentWidth > 0)
+        verify(textArea.contentHeight > 200)
+
+        compare(control.contentWidth, textArea.contentWidth + textArea.leftPadding + textArea.rightPadding)
+        compare(control.contentHeight, textArea.contentHeight + textArea.topPadding + textArea.bottomPadding)
+
+        control.destroy()
+    }
+
+    function test_warning() {
+        ignoreWarning(Qt.resolvedUrl("tst_textarea.qml") + ":45:1: QML TestCase: TextArea must be attached to a Flickable")
+        testCase.TextArea.flickable = null
+    }
 }