diff options
Diffstat (limited to 'doc/src/porting/porting4-canvas.qdoc')
| -rw-r--r-- | doc/src/porting/porting4-canvas.qdoc | 702 |
1 files changed, 702 insertions, 0 deletions
diff --git a/doc/src/porting/porting4-canvas.qdoc b/doc/src/porting/porting4-canvas.qdoc new file mode 100644 index 0000000..5435723 --- /dev/null +++ b/doc/src/porting/porting4-canvas.qdoc @@ -0,0 +1,702 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** GNU Lesser General Public License Usage +** Alternatively, 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 1.0, 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. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at http://qt.nokia.com/contact. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \page graphicsview-porting.html + \title Porting to Graphics View + \contentspage {Porting Guides}{Contents} + \previouspage Porting UI Files to Qt 4 + \nextpage qt3to4 - The Qt 3 to 4 Porting Tool + \ingroup porting + \brief Hints and tips to assist with porting canvas applications to the + Graphics View framework. + + \keyword QGraphicsView GraphicsView Porting Graphics Canvas + \since 4.2 + + Graphics View provides a surface for managing and interacting with a large + number of custom-made 2D graphical items, and a view widget for + visualizing the items, with support for zooming and rotation. Graphics + View was introduced in Qt 4.2, replacing its predecessor, QCanvas. For + more on Graphics View, see \l{The Graphics View Framework}. + + This document walks through the steps needed, class by class and function + by function, to port a QCanvas application to Graphics View. + + \tableofcontents + + Qt 4.2 provides two complete examples of Q3Canvas applications ported to + Graphics View: + + \list + \o \l{Ported Canvas Example}, the canvas example from Qt 3. + \o \l{Ported Asteroids Example}, the Asteroids game from the Qt 3 demo. + \endlist + + \section1 Introduction + + Conceptually, the Graphics View classes from Qt 4 and the Canvas + classes from Qt 3 provide similar functionality using a similar + design. Instead of "canvas", we use the term "scene". Otherwise, the + class names and functions are almost the same as in Qt 3. The easiest + classes to port will be QCanvas and QCanvasView. Experience shows that + most time is spent porting the item classes, depending on the + complexity of the QCanvasItem classes you have been using before. + + This porting guide will assume you have already ported your + application to Qt 4, by making use of Q3Canvas. If you have not done + so already, as a first step, run the \l qt3to4 tool on your + project. This tool will automate the most tedious part of the porting + effort. + + Some additional steps are usually required before your application + will compile and run. You can read more about the porting process in + \l{Porting to Qt 4}. + + \section1 Porting from Q3Canvas + + QGraphicsScene is the closest equivalent to Q3Canvas. There + are some noticable differences in this new API: Whereas the + Q3Canvas classes use integer precision, QGraphicsScene is + entirely based on double coordinates, with graphical + primitives such as QPointF instead of QPoint, QRectF instead + of QRect, and QPolygonF and QPainterPath. The canvas area is + defined by a scene rectangle, allowing negative coordinates, + as opposed to Q3Canvas, which only defines a size (QSize), and + whose top-left corner is always (0, 0). + + In addition, there is no explicit support for canvas tiles + anymore; see \l{Porting scenes with tiles} for more + information. The chunks-based indexing system has been + replaced with an implicitly maintained internal BSP tree. + + \section2 Porting table + + \table + \header \o Q3Canvas \o QGraphicsScene + + \row \o Q3Canvas::Q3Canvas() \o There is no QPixmap based + constructor, and the concept of tiles is gone. You can use + QGraphicsScene::backgroundBrush to set a brush pattern for + the background, or reimplement + QGraphicsScene::drawBackground() in a QGraphicsScene + subclass (see \l{Porting scenes with tiles}). In addition, + the QGraphicsScene geometry is provided as a full + QRectF. Instead of Q3Canvas(int width, int height), you can + use QGraphicsScene(int top, int left, int width, int + height). + + \row \o Q3Canvas::allItems() \o QGraphicsScene::items() + returns a list of all items on the scene. + + \row \o Q3Canvas::backgroundColor() \o You can assign a color for the + background through the QGraphicsScene::backgroundBrush + or QGraphicsView::backgroundBrush properties. + + \row \o Q3Canvas::backgroundPixmap() \o You can set a tiled + pixmap for the background through + QGraphicsScene::backgroundBrush or + QGraphicsView::backgroundBrush. For more control on the pixmap + positioning, you can reimplement + QGraphicsScene::drawBackground() or + QGraphicsView::drawBackground(). + + \row \o Q3Canvas::chunkSize() \o The closest equivalent to the + chunks size in Q3Canvas is the depth of QGraphicsScene's BSP + tree. QGraphicsScene assigns a depth automatically, and the + size of each scene segment depends on this depth, and + QGraphicsScene::sceneRect(). See + QGraphicsScene::itemIndexMethod. + + \row \o Q3Canvas::collisions() \o QGraphicsScene provides + several means to detect item collisions. The + QGraphicsScene::items() overloads return items that collide + with a point, a rectangle, a polygon, or an arbitrary vector + path (QPainterPath). You can also call + QGraphicsScene::collidingItems() to determine collision with + an item. + + \row \o Q3Canvas::drawArea() \o The QGraphicsScene::render() + function provides the original behavior + Q3Canvas::drawArea(). In addition, you can pass a source + rectangle for rendering only parts of the scene, and a + destination rectangle for rendering onto designated area of + the destination device. QGraphicsScene::render() can + optionally transform the source rectangle to fit into the + destination rectangle. See \l{Printing} + + \row \o Q3Canvas::onCanvas() \o The is no equivalent to this + function in Graphics View. However, you can combine + QGraphicsScene::sceneRect() and QRectF::intersects(): + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 0 + + \row \o Q3Canvas::rect() \o The equivalent, + QGraphicsScene::sceneRect(), returns a QRectF (double + precision coordinates). Its top-left corner can be an + arbitrary coordinate (Q3Canvas::rect().topLeft() is always (0, + 0)). + + \row \o Q3Canvas::resize() \o You can call + QGraphicsScene::setSceneRect(0, 0, width, height) instead. + + \row \o Q3Canvas::retune() \o See + QGraphicsScene::itemIndexMethod. You can tune the indexing by + setting a suitable sceneRect(). The optimal depth of + QGraphicsScene's BSP tree is determined automatically. + + \row \o Q3Canvas::setAdvancePeriod() \o There is no concept of + an advance period in the new API; instead, you can connect + QTimer::timeout() to the QGraphicsScene::advance() slot to + obtain similar functionality. This will cause all items' + QGraphicsItem::advance() function to be called. See also + QGraphicsItemAnimation. + + \row \o Q3Canvas::setAllChanged() \o You can call + QGraphicsScene::update() with no arguments. + + \row \o Q3Canvas::setChanged() \o QGraphicsScene::update() + will trigger a repaint of the whole scene, or parts of the + scene. + + \row \o Q3Canvas::setDoubleBuffering() \o Q3Canvas' double + buffering enabled cacheing of the scene contents in device + (i.e., viewport) coordinates. This cache layer has been moved + to the view instead; you can cache QGraphicsScene's background + through + QGraphicsView::setCacheMode(). QGraphicsView::resetCachedContent() + will reset the areas of the cache that has changed. + + \row \o Q3Canvas::tile() \o See \l{Porting scenes with tiles}. + + \row \o Q3Canvas::setTiles() \o See \l{Porting scenes with tiles}. + + \row \o Q3Canvas::setUnchanged() \o There is no equivalent in + Graphics View. This call can usually be removed with no side + effects. + + \row \o Q3Canvas::setUpdatePeriod() \o There is no concept of an + update period in the new API; instead, you can connect + QTimer::timeout() to the QGraphicsScene::update() slot to obtain + similar functionality. See also QGraphicsItemAnimation. + + \row \o Q3Canvas::size() \o + \tt{QGraphicsScene::sceneRect().size()} returns a QSizeF, with + double precision coordinates. + + \row \o Q3Canvas::validChunk() \o To determine if an area is + inside the scene area or not, you can combine + QRectF::intersects() with QGraphicsScene::sceneRect(). + + \row \o Q3Canvas::resized() \o QGraphicsScene emits + \l{QGraphicsScene::sceneRectChanged()}{sceneRectChanged()} + whenever the scene rect changes. + + \row \o Q3Canvas::drawBackground() \o You can reimplement + QGraphicsScene::drawBackground() to render the scene + background. You can also reimplement + QGraphicsView::drawBackground() to override this background if + you need different backgrounds for different views. + + \row \o Q3Canvas::drawForeground() \o You can reimplement + QGraphicsScene::drawForeground() to render the scene + foreground. You can also reimplement + QGraphicsView::drawForeground() to override this foreground if + you need different foregrounds for different views. + + \endtable + + \section2 Porting scenes with tiles + + QGraphicsScene does not provide an API for tiles. However, you + can achieve similar behavior by drawing pixmaps in a reimplementation of + QGraphicsScene::drawBackground(). + + Q3Canvas' tile support is based on providing one pixmap + containing tiles of a fixed width and height, and then + accessing them (reading and replacing tiles) by index. The + tiles in the pixmap are arranged from the left to right, top + to bottom. + + \table + \row \i 0 \i 1 \i 2 \i 3 + \row \i 4 \i 5 \i 6 \i 7 + \endtable + + With Graphics View, this pixmap can be stored as a member of a + subclass of QGraphicsScene. The three main functions that make + out the public tile API can then be declared as new members of + this class. Here is one example of how to implement tile support: + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 1 + + Depending on how your scene uses tiles, you may be able to + simplify this approach. In this example, we will try to mimic the behavior + of the Q3Canvas functions. + + We start by creating a subclass of QGraphicsScene ("TileScene"). + In this class, we declare two of the tile + functions from Q3Canvas, and we then add two helper function that returns the + rectangle for a certain tile in our tile pixmap. We will use a + two-dimensional vector of ints to keep track of what tiles should + be used at what parts of the scene. + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 2 + + In setTiles(), we store the pixmap and tile properties as + members of the class. Then we resize the tiles vector + to match the width and height of our tile grid. + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 3 + + The setTile() function updates the tiles index, and then + updates the corresponding rect in the scene by calling + tileRect(). + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 4 + + The first tileRect() function returns a QRect for the tile at + position (x, y). + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 5 + + The second tileRect() function returns a QRect for a tile number. + With these functions in place, we can implement the drawBackground() + function. + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 6 + + In drawBackground(), we redraw all tiles that have been + exposed by intersecting each tile rect with the exposed background + area. + + \section1 Porting from Q3CanvasView + + The closest equivalent to Q3CanvasView in Graphics View is + called QGraphicsView. In most cases, this is the easiest + class to port. In addition to providing all of Q3CanvasView's + functionality, QGraphicsView includes some useful new features. You + can read more about this in QGraphicsView's documentation. + + \section2 Porting table + + \table + \header \o Q3CanvasView \o QGraphicsView + + \row \o Q3CanvasView::Q3CanvasView() \o QGraphicsView provides + the same constructors as Q3CanvasView, but without the name + and flags arguments. You can set the name by calling + \l{QWidget::setObjectName()}{setObjectName()}, and the flags by + calling \l{QWidget::setWindowFlags()}{setWindowFlags()}. + + \row \o Q3CanvasView::canvas() \o QGraphicsView::scene() + returns the scene that is currently associated with the + view. QGraphicsScene also provides the opposite function, + QGraphicsScene::views(), which returns a list of views + observing the scene. + + \row \o Q3CanvasView::inverseWorldMatrix() \o You can call + QGraphicsView::matrix() and QMatrix::inverted(). + QGraphicsView::mapToScene() and QGraphicsView::mapFromScene() + allow transforming of viewport shapes to scene shapes, and + vice versa. + + \row \o Q3CanvasView::setCanvas() \o QGraphicsView::setScene(). + + \row \o Q3CanvasView::setWorldMatrix() \o + QGraphicsView::setMatrix(), QGraphicsView::rotate(), + QGraphicsView::scale(), QGraphicsView::shear() and + QGraphicsView::translate(). + + \row \o Q3CanvasView::worldMatrix() \o QGraphicsView::matrix() + + \row \o Q3CanvasView::drawContents() \o The + QGraphicsView::drawBackground() function draws the background, + QGraphicsView::drawItems() draws the items, and + QGraphicsView::drawForeground() draws the foreground of the + scene in scene coordinates. You can also reimplement these + functions in QGraphicsScene. + + \endtable + + \section2 Other differences + + QGraphicsView can cache the visible contents of the scene, + similar to how Q3Canvas::setDoubleBuffering() could cache the + entire scene contents. You can call + QGraphicsView::setCacheMode() to configure cacheing, and + QGraphicsView::resetCachedContent() invalidates the cache. + + For improved navigation support, you can set a resize or + transformation anchor through QGraphicsView::resizeAnchor and + QGraphicsView::transformationAnchor. This allows you to easily + rotate and zoom the view while keeping the center fixed, or + zooming towards the position under the mouse cursor. In + addition, if you set the QGraphicsView::dragMode of the view, + QGraphicsView will provide rubber band selection or + click-and-pull navigation using the + \l{Qt::OpenHandCursor}{OpenHandCursor} and + \l{Qt::ClosedHandCursor}{ClosedHandCursor} cursors. + + \section1 Porting from Q3CanvasItem + + The closest equivalent to Q3CanvasItem in Graphics View is + called QGraphicsItem. Deriving from this class is very common, + and because of that, porting from Q3CanvasItem often involves + more work than Q3Canvas and Q3CanvasView. + + Q3CanvasItem has become easier to use, easier to subclass, and more + powerful with QGraphicsItem. The key difference from Q3CanvasItem lies + in event propagation and item groups, but you will also find several + convenient new features, such as support for tooltips, cursors, item + transformation and drag and drop. You can read all about QGraphicsItem + in its own class documentation. + + This section starts with a table that shows how to port each function + from Q3CanvasItem to QGraphicsItem. Immediately after that, each of + Q3CanvasItem's standard subclasses have a section of their own. + + \table + \header \o Q3CanvasItem \o QGraphicsItem + + \row \o Q3CanvasItem::advance() \o QGraphicsItem::advance() is + provided for compatibility. QGraphicsScene::advance() calls + QGraphicsItem::advance() for all items. See also QTimeLine and + QGraphicsItemAnimation. + + \row \o Q3CanvasItem::animated() \o No equivalent; all items + are advanced by QGraphicsScene::advance(). + + \row \o Q3CanvasItem::boundingRectAdvanced() \o No + equivalent. You can translate QGraphicsItem::boundingRect() + instead (see QRectF::translate()). + + \row \o Q3CanvasItem::canvas() \o QGraphicsItem::scene() + + \row \o Q3CanvasItem::collidesWith() \o + QGraphicsItem::collidesWithItem() and + QGraphicsItem::collidesWithPath(). + + \row \o Q3CanvasItem::collisions() \o + QGraphicsItem::collidingItems() returns a list of all items + that collide with an item. You can specify whether you want + fast, rough estimate collision between bounding rectangles, or + the slower, more accurate shapes. + + \row \o Q3CanvasItem::draw() \o QGraphicsItem::paint(). See + also QStyleOptionGraphicsItem, QGraphicsScene::drawItems() and + QGraphicsView::drawItems(). + + \row \o Q3CanvasItem::hide() \o QGraphicsItem::hide() or + QGraphicsItem::setVisible(). \l{QGraphicsItem}s are \e visible by + default; \l{Q3CanvasItem}s, however, are not. + + \row \o Q3CanvasItem::isActive() \o No equivalent. To achieve + similar behavior, you can add this property in a custom + subclass of QGraphicsItem. + + \row \o Q3CanvasItem::isVisible() \o + QGraphicsItem::isVisible(). \l{QGraphicsItem}s are \e visible by + default; \l{Q3CanvasItem}s, however, are not. + + \row \o Q3CanvasItem::move() \o You can call + QGraphicsItem::setPos() to change the position of the item. + + \row \o Q3CanvasItem::rtti() \o QGraphicsItem::type() and qgraphicsitem_cast(). + + \row \o Q3CanvasItem::setActive() \o No equivalent. + + \row \o Q3CanvasItem::setAnimated() \o No equivalent; all + items are by default "animated" (i.e., + QGraphicsScene::advance() advances all items on the scene). + + \row \o Q3CanvasItem::setCanvas() \o You can call + QGraphicsScene::addItem(), or pass a pointer to the canvas to + QGraphicsItem's constructor. + + \row \o Q3CanvasItem::setVelocity() \o No equivalent. You can + add x and y velocity as member data of your class, and call + QGraphicsItem::moveBy(x, y) from inside + QGraphicsItem::advance(). See also QTimeLine and + QGraphicsItemAnimation. + + \row \o Q3CanvasItem::setVisible() \o + QGraphicsItem::setVisible(). \l{QGraphicsItem}s are \e visible by + default; \l{Q3CanvasItem}s, however, are not. + + \row \o Q3CanvasItem::setX() \o QGraphicsItem::setPos() + \row \o Q3CanvasItem::setY() \o QGraphicsItem::setPos() + + \row \o Q3CanvasItem::setXVelocity() \o No equivalent. + \row \o Q3CanvasItem::setYVelocity() \o No equivalent. + + \row \o Q3CanvasItem::setZ() \o QGraphicsItem::setZValue() + + \row \o Q3CanvasItem::show() \o QGraphicsItem::show() or + QGraphicsItem::setVisible(). \l{QGraphicsItem}s are \e visible by + default; \l{Q3CanvasItem}s, however, are not. + + \row \o Q3CanvasItem::xVelocity() \o No equivalent. + \row \o Q3CanvasItem::yVelocity() \o No equivalent. + + \endtable + + Note that some virtual functions that have passed on to + QGraphicsItem have lost their virtuality. An example is + Q3CanvasItem::moveBy(), which was often used to track movement of + items. In this case, the virtual QGraphicsItem::itemChange() has + taken over as a substitute. + + \section2 Q3CanvasPolygonalItem + + The closest equivalent to Q3CanvasPolygonalItem in + Graphics View is called QAbstractGraphicsShapeItem. Unlike + Q3CanvasPolygonalItem, it does not define area points + (Q3CanvasPolygonalItem::areaPoints()); instead, each + item's geometry is stored as a member of the subclasses. + + The Q3CanvasPolygonalItem::drawShape() function is no longer + available; instead, you can set the brush and pen from inside + QGraphicsItem::paint(). + + \table + \header \o Q3CanvasPolygonalItem \o QAbstractGraphicsShapeItem + + \row \o Q3CanvasPolygonalItem::areaPoints() \o No equivalent; each + item's geometry is stored in the respective subclass. + + \row \o Q3CanvasPolygonalItem::areaPointsAdvanced() \o No + equivalent; you can use QPolygonF::translate() or + QPainterPath::translate() instead. + + \row \o Q3CanvasPolygonalItem::drawShape() \o + QGraphicsItem::paint(). You can set the pen and brush from inside + this function. + + \row \o Q3CanvasPolygonalItem::invalidate() \o Call + QGraphicsItem::prepareGeometryChange() before changing the + item's geometry. + + \row \o Q3CanvasPolygonalItem::isValid() \o No equivalent; + items' geometry is always in a valid state. + + \row \o Q3CanvasPolygonalItem::winding() \o This function is only + useful for polygon items and path items; see + QGraphicsPolygonItem::fillRule(), and QPainterPath::fillRule() for + QGraphicsPathItem. + + \endtable + + \section2 Q3CanvasEllipse + + The closest equivalent to Q3CanvasEllipse in Graphics View + is called QGraphicsEllipseItem. The most noticable + difference to QGraphicsEllipseItem is that the ellipse is + not longer drawn centered around its position; rather, it + is drawn using a bounding QRectF, just like + QPainter::drawEllipse(). + + For compatibility, you may want to shift the ellipse up and to the + left to keep the ellipse centered. Example: + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 7 + + Note: QGraphicsEllipseItem uses QAbstractGraphicsShapeItem::pen() + for outlines, whereas Q3CanvasEllipse did not use + Q3CanvasPolygonalItem::pen(). + + \table + \header \o Q3CanvasEllipse \o QGraphicsEllipseItem + + \row \o Q3CanvasEllipse::angleLength() \o QGraphicsEllipseItem::spanAngle() + + \row \o Q3CanvasEllipse::angleStart() \o QGraphicsEllipseItem::startAngle() + + \row \o Q3CanvasEllipse::setAngles() \o + QGraphicsEllipseItem::setStartAngle() and + QGraphicsEllipseItem::setSpanAngle() + + \row \o Q3CanvasEllipse::setSize() \o QGraphicsEllipseItem::setRect() + + \endtable + + \section2 Q3CanvasLine + + The closest equivalent to Q3CanvasLine in Graphics View is + called QGraphicsLineItem. + + \table + \header \o Q3CanvasLine \o QGraphicsLineItem + + \row \o Q3CanvasLine::endPoint() \o QGraphicsLineItem::line() and QLineF::p2() + + \row \o Q3CanvasLine::setPoints() \o QGraphicsLineItem::setLine() + + \row \o Q3CanvasLine::startPoint() \o QGraphicsLineItem::line() + and QLineF::p1() + + \endtable + + \section2 Q3CanvasPolygon + + The closest equivalent to Q3CanvasPolygon in Graphics View + is called QGraphicsPolygonItem. + + \table + \header \o Q3CanvasPolygon \o QGraphicsPolygonItem + + \row \o Q3CanvasPolygon::areaPoints() \o + QGraphicsPolygonItem::polygon() and QGraphicsItem::mapToParent() + + \row \o Q3CanvasPolygon::points() \o QGraphicsPolygonItem::polygon() + + \row \o Q3CanvasPolygon::setPoints() \o QGraphicsPolygonItem::setPolygon() + + \endtable + + \section2 Q3CanvasSpline + + The closest equivalent to Q3CanvasSpline in Graphics View + is called QGraphicsPathItem. This item can be used to + describe any type of path supported by QPainter. + + Q3CanvasSpline takes its control points as a Q3PointArray, but + QPainterPath operates on a sequence of calls to + QPainterPath::moveTo() and QPainterPath::cubicTo(). Here is how + you can convert a bezier curve Q3PointArray to a QPainterPath: + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 8 + + Note: QGraphicsPathItem uses QAbstractGraphicsShapeItem::pen() for + outlines, whereas Q3CanvasSpline did not use + Q3CanvasPolygonalItem::pen(). + + \table + \header \o Q3CanvasSpline \o QGraphicsPathItem + + \row \o Q3CanvasSpline::closed() \o No equivalent. You can call + QPainterPath::closeSubPath() to close a subpath explicitly. + + \endtable + + \section2 Q3CanvasRectangle + + The closest equivalent to Q3CanvasRectangle in Graphics + View is called QGraphicsRectItem. + + \table + \header \o Q3CanvasRectangle \o QGraphicsRectItem + + \row \o Q3CanvasRectangle::height() \o QGraphicsRectItem::rect() + and QRectF::height() + + \row \o Q3CanvasRectangle::setSize() \o QGraphicsRectItem::setRect() + + \row \o Q3CanvasRectangle::size() \o QGraphicsRectItem::rect() and QRectF::size() + + \row \o Q3CanvasRectangle::width() \o QGraphicsRectItem::rect() and QRectF::width() + + \row \o Q3CanvasRectangle::chunks() \o No equivalent. + + \endtable + + \section2 Q3CanvasSprite + + Q3CanvasSprite is the item class that differs the most from its + Q3Canvas predecessor. The closest resemblance of Q3CanvasSprite in + Graphics View is QGraphicsPixmapItem. + + Q3CanvasSprite supports animated pixmaps; QGraphicsPixmapItem, + however, is a simple single-frame pixmap item. If all you need is + a pixmap item, porting is straight-forward. If you do need the + animation support, extra work is required; there is no direct + porting approach. + + For the \l{Ported Asteroids Example}, a subclass of + QGraphicsPixmapItem is used to replace Q3CanvasSprite, storing a + list of pixmaps and a frame counter. The animation is advanced in + QGraphicsItem::advance(). + + \section3 Q3CanvasPixmap, Q3CanvasPixmapArray + + These classes have been removed from the API. You can use + QPixmap instead of Q3CanvasPixmap, and QList instead of + Q3CanvasPixmapArray. + + Q3CanvasPixmapArray included convenience for loading a + sequence of pixmaps or masks using a path with a wildcard (see + Q3CanvasPixmapArray::readPixmaps() and + Q3CanvasPixmapArray::readCollisionMasks()). To achieve similar + functionality using Graphics View, you can load the images by + using QDir: + + \snippet doc/src/snippets/code/doc_src_porting4-canvas.qdoc 9 + + \section2 Q3CanvasText + + Q3CanvasText has been split into two classes in Graphics View: + QGraphicsSimpleTextItem and QGraphicsTextItem. For porting, + QGraphicsSimpleTextItem should be adequate. QGraphicsTextItem + provides advanced document structuring features similar to that of + QTextEdit, and it also allows interaction (e.g., editing and + selection). + + \table + \header \o Q3CanvasText \o QGraphicsSimpleTextItem + + \row \o Q3CanvasText::color() \o QGraphicsSimpleTextItem::pen(). + + \row \o Q3CanvasText::setColor() \o QGraphicsSimpleTextItem::setPen(). + + \row \o Q3CanvasText::textFlags() \o Use QGraphicsTextItem instead. + + \endtable + + + \section2 Q3CanvasItemList + + Use QList instead. + + \section1 Other Resources + + The \l{Porting to Qt 4.2's Graphics View} article in Qt Quarterly 21 covered the + process of porting the Qt 3 canvas example to Qt 4. + The result of this is the \l{Ported Canvas Example}{Ported Canvas} example. +*/ |