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authorAndreas Aardal Hanssen <andreas.aardal.hanssen@nokia.com>2010-05-12 14:32:12 (GMT)
committerAndreas Aardal Hanssen <andreas.aardal.hanssen@nokia.com>2010-05-12 14:36:10 (GMT)
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Documentation for the Pad Navigator Example.
This also does a few touch-ups on the source code.
Diffstat (limited to 'doc/src')
-rw-r--r--doc/src/examples/padnavigator.qdoc552
-rw-r--r--doc/src/getting-started/examples.qdoc1
2 files changed, 550 insertions, 3 deletions
diff --git a/doc/src/examples/padnavigator.qdoc b/doc/src/examples/padnavigator.qdoc
index 70e131e..e29a3b2 100644
--- a/doc/src/examples/padnavigator.qdoc
+++ b/doc/src/examples/padnavigator.qdoc
@@ -43,9 +43,555 @@
\example graphicsview/padnavigator
\title Pad Navigator Example
- The Pad Navigator Example shows how you can use Graphics View
- together with embedded widgets to create a simple but useful
- dynamic user interface for embedded devices.
+ The Pad Navigator Example shows how you can use Graphics View together with
+ embedded widgets and Qt's \l{State Machine Framework} to create a simple
+ but useful, dynamic, animated user interface.
\image padnavigator-example.png
+
+ The interface consists of a flippable, rotating pad with icons that can be
+ selected using the arrow keys on your keyboard or keypad. Pressing enter
+ will flip the pad around and reveal its back side, which has a form
+ embedded into a QGraphicsProxyWidget. You can interact with the form, and
+ press the enter key to flip back to the front side of the pad at any time.
+
+ Graphics View provides the QGraphicsScene class for managing and
+ interacting with a large number of custom-made 2D graphical items derived
+ from the QGraphicsItem class, and a QGraphicsView widget for visualizing
+ the items, with support for zooming and rotation.
+
+ This example consists of a \c RoundRectItem class, a \c FlippablePad class,
+ a \c PadNavigator class, a \c SplashItem class, and a \c main() function.
+
+ \section1 RoundRectItem Class Definition
+
+ The \c RoundRectItem class is used by itself to diplay the icons on the
+ pad, and as a base class for \c FlippablePad, the class for the pad itself.
+ The role of the class is to paint a round rectangle of a specified size and
+ gradient color, and optionally to paint a pixmap icon on top. To support \c
+ FlippablePad it also allows filling its contents with a plain window
+ background color.
+
+ Let's start by reviewing the \c RoundRectItem class declaration.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.h 0
+
+ \c RoundRectItem inherits QGraphicsObject, which makes it easy to control
+ its properties using QPropertyAnimation. Its constructor takes a rectangle
+ to determine its bounds, and a color.
+
+ Besides implementing the mandatory \l{QGraphicsItem::paint()}{paint()} and
+ \l{QGraphicsItem::boundingRect()}{boundingRect()} pure virtual functions,
+ it also provides the \c pixmap and \c fill properties.
+
+ The \c pixmap property sets an optional pixmap that is drawn on top of the
+ round rectangle. The \c fill property will, when true, fill the round
+ rectangle contents with a fixed QPalette::Window background color.
+ Otherwise the contents are filled using a gradient based on the color
+ passed to \c RoundRectItem's constructor.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.h 1
+
+ The private data members are:
+
+ \list
+ \o \c pix: The optional pixmap that is drawn on top of the rectangle.
+ \o \c fillRect: Corresponds to the \c fill property.
+ \o \c color: The configurable gradient color fill of the rectangle.
+ \o \c bounds: The bounds of the rectangle.
+ \o \c gradient: A precalculated gradient used to fill the rectangle.
+ \endlist
+
+ We will now review the \c RoundRectItem implementation. Let's start by
+ looking at its constructor:
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 0
+
+ The constructor initializes its member variables and forwards the \c parent
+ argument to QGraphicsObject's constructor. It then constructs the linear
+ gradient that is used in \l{QGraphicsItem::paint()}{paint()} to draw the
+ round rectangle's gradient background. The linear gradient's starting point
+ is at the top-left corner of the bounds, and the end is at the bottom-left
+ corner. The start color is identical to the color passed as an argument,
+ and a slightly darker color is chosen for the final stop.
+
+ We store this gradient as a member variable to avoid having to recreate the
+ gradient every time the item is repainted.
+
+ Finally we set the cache mode
+ \l{QGraphicsItem::ItemCoordinateCache}{ItemCoordinateCache}. This mode
+ causes the item's rendering to be cached into an off-screen pixmap that
+ remains persistent as we move and transform the item. This mode is ideal
+ for this example, and works particularily well with OpenGL and OpenGL ES.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 1
+
+ The \c pixmap property implementation simple returns the member pixmap, or
+ sets it and then calls \l{QGraphicsItem::update()}{update()}.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 2
+
+ As the \l{QGraphicsItem::paint()}{paint()} implementation below draws a
+ simple drop shadow down and to the right of the item, we return a slightly
+ adjusted rectangle from \l{QGraphicsItem::boundingRect()}{boundingRect()}.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 3
+
+ The \l{QGraphicsItem::paint()}{paint()} implementation starts by rendering
+ a semi transparent black round rectangle drop shadow, two units down and to
+ the right of the main item.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 4
+
+ We then draw the "foreground" round rectangle itself. The fill depends on
+ the \c fill property; if true, we will with a plain QPalette::Window color.
+ We get the corrent brush from QApplication::palette(). We assign a single
+ unit wide pen for the stroke, assign the brush, and then draw the
+ rectangle.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 5
+
+ If a pixmap has been assigned to the \e pixmap property, we draw this
+ pixmap in the center of the rectangle item. The pixmaps are scaled to match
+ the size of the icons; in arguably a better approach would have been to
+ store the icons with the right size in the first places.
+
+ \snippet examples/graphicsview/padnavigator/roundrectitem.cpp 6
+
+ Finally, for completeness we include the \c fill property implementation.
+ It returns the \c fill member variable's value, and when assigned to, it
+ calls \l{QGraphicsItem::update()}{update()}.
+
+ As mentioned already, \c RoundRectItem is the base class for \c
+ FlippablePad, which is the class representing the tilting pad itself. We
+ will proceed to reviewing \c FlippablePad.
+
+ \section1 FlippablePad Class Definition
+
+ \c FlippablePad is, in addition to its inherited \c RoundRectItem
+ responsibilities, responsible for creating and managing a grid of icons.
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.h 0
+
+ Its declaration is very simple: It inherits \c RoundRectItem and does not
+ need any special polymorphic behavior. It's suitable to declare its own
+ constructor, and a getter-function that allows \c PadNavigator to access
+ the icons in the grid by (row, column).
+
+ The example has no "real" behavior or logic of any kind, and because of
+ that, the icons do not need to provide any \e behavior or special
+ interactions management. In a real application, however, it would be
+ natural for the \c FlippablePad and its icons to handle more of the
+ navigation logic. In this example, we have chosen to leave this to
+ the \c PadNavigator class, which we will get back to below.
+
+ We will now review the \c FlippablePad implementation. This implementation
+ starts with two helper functions: \c boundsFromSize() and \c
+ posForLocation():
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.cpp 0
+
+ \c boundsForSize() takes a QSize argument, and returns the bounding
+ rectangle of the flippable pad item. The QSize determines how many rows and
+ columns the icon grid should have. Each icon is given 150x150 units of
+ space, and this determines the bounds.
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.cpp 1
+
+ \c posForLocation() returns the position of an icon given its row and
+ column position. Like \c boundsForSize(), the function assumes each icon is
+ given 150x150 units of space, and that all icons are centered around the
+ flippable pad item's origin (0, 0).
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.cpp 2
+
+ The \c FlippablePad constructor passes suitable bounds (using \c
+ boundsForSize()) and specific color to \c RoundRectItem's constructor.
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.cpp 3
+
+ It then loads pixmaps from compiled-in resources to use for its icons.
+ QDirIterator is very useful in this context, as it allows us to fetch all
+ resource "*.png" files inside the \c :/images directory without explicitly
+ naming the files.
+
+ We also make sure not to load more pixmaps than we need.
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.cpp 4
+
+ Now that we have the pixmaps, we can create icons, position then and assign
+ pixmaps. We start by finding a suitable size and color for the icons, and
+ initializing a convenient grid structure for storing the icons. This \c
+ iconGrid is also used later to find the icon for a specific (column, row)
+ location.
+
+ For each row and column in our grid, we proceed to constructing each icon
+ as an instance of \c RoundRectItem. The item is placed by using the \c
+ posForLocation() helper function. To make room for the slip-behind
+ selection item, we give each icon a \l{QGraphicsItem::zValue()}{Z-value} of
+ 1. The pixmaps are distributed to the icons in round-robin fasion.
+
+ Again, this approach is only suitable for example purposes. In a real-life
+ application where each icon represents a specific action, it would be more
+ natural to assign the pixmaps directly, or that the icons themselves
+ provide suitable pixmaps.
+
+ \snippet examples/graphicsview/padnavigator/flippablepad.cpp 5
+
+ Finally, the \c iconAt() function returns a pointer to the icon at a
+ specific row and column. It makes a somewhat bold assumption that the input
+ is valid, which is fair because the \c PadNavigator class only calls this
+ function with correct input.
+
+ We will now review the \c SplashItem class.
+
+ \section1 SplashItem Class Definition
+
+ The \c SplashItem class represents the "splash window", a semitransparent
+ white overlay with text that appears immediately after the application has
+ started, and disappears after pressing any key. The animation is controlled
+ by \c PadNavigator; this class is very simple by itself.
+
+ \snippet examples/graphicsview/padnavigator/splashitem.h 0
+
+ The class declaration shows that \c SplashItem inherits QGraphicsObject to
+ allow it to be controlled by QPropertyAnimation. It reimplements the
+ mandatory \l{QGraphicsItem::paint()}{paint()} and
+ \l{QGraphicsItem::boundingRect()}{boundingRect()} pure virtual functions,
+ and keeps a \c text member variable which will contain the information text
+ displayed on this splash item.
+
+ Let's look at its implementation.
+
+ \snippet examples/graphicsview/padnavigator/splashitem.cpp 0
+
+ The constructor forwards to QGraphicsObject as expected, assigns a text
+ message to the \c text member variable, and enables
+ \l{QGraphicsItem::DeviceCoordinateCache}{DeviceCoordinateCache}. This cache
+ mode is suitable because the splash item only moves and is never
+ transformed, and because it contains text, it's important that it has a
+ pixel perfect visual appearance (in constrast to
+ \l{QGraphicsItem::ItemCoordinateCache}{ItemCoordinateCache}, where the
+ visual appearance is not as good).
+
+ We use caching to avoid having to relayout and rerender the text for each
+ frame. An alterative approach would be to use the new QStaticText class.
+
+ \snippet examples/graphicsview/padnavigator/splashitem.cpp 1
+
+ \c SplashItem's bounding rectangle is fixed at (400x175).
+
+ \snippet examples/graphicsview/padnavigator/splashitem.cpp 2
+
+ The \l{QGraphicsItem::paint()}{paint()} implementation draws a clipped
+ round rectangle with a thick 2-unit border and a semi-transparent white
+ background. It proceeds to finding a suitable text area by adjusting the
+ splash item's bounding rectangle with 10 units in each side. The text is
+ rendered inside this rectangle, with top-left alignment, and with word
+ wrapping enabled.
+
+ The main class now remains. We will proceed to reviewing \c PadNavigator.
+
+ \section1 PadNavigator Class Definition
+
+ \c PadNavigator represents the main window of our Pad Navigator Example
+ application. It creates and controls a somewhat complex state machine, and
+ several animations. Its class declaration is very simple:
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.h 0
+
+ It inherits QGraphicsView and reimplements only one function:
+ \l{QGraphicsView::resizeEvent()}{resizeEvent()}, to ensure the scene is
+ scaled to fit inside the view when resizing the main window.
+
+ The \c PadNavigator constructor takes a QSize argument that determines the
+ number or rows and columns in the grid.
+
+ It also keeps a private member instance, \c form, which is the generated
+ code for the pad's back side item's QGraphicsProxyWidget-embedded form.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 0
+
+ \c PadNavigator's constructor is a bit long. In short, its job is to create
+ all items, including the \c FlippablePad, the \c SplashItem and the
+ QGraphicsProxyWidget \c backItem, and then to set up all animations, states
+ and transitions that control the behavior of the application.
+
+ It starts out simple, by forwarding to QGraphicsView's constructor.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 1
+
+ The first item to be created is \c SplashItem. This is going to be a top-level
+ item in the scene, next to \c FlippablePad, and stacked on top of it, so we
+ assign it a \l{QGraphicsItem::zValue()}{Z-value} of 1.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 2
+
+ Now we construct the \c FlippablePad item, passing its column-row count to
+ its constructor.
+
+ The pad is constrolled by three transformations, and we create one
+ QGraphicsRotation object for each of these.
+
+ \list
+ \o \c flipRotation: Rotates the grid around its Qt::YAxis. This rotation is
+ animated from 0 to 180, and eventually back, when enter is pressed on the
+ keyboard, flipping the pad around.
+ \o \c xRotation: Rotates the grid around its Qt::XAxis. This is used to
+ tilt the pad vertically corresponding to which item is currently selected.
+ This way, the selected item is always kept in front.
+ \o \c yRotation: Rotates the grid around its Qt::YAxis. This is used to
+ tilt the pad horizontally corresponding to which item is selected. This
+ way, the selected item is always kept in front.
+ \endlist
+
+ The combination of all three rotations is assigned via
+ QGraphicsItem::setTransformations().
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 3
+
+ Now we construct the QGraphicsProxyWidget-embedded \c backItem. The proxy
+ widget is created as a child of the pad. We create a new QWidget and
+ populate it with the \c form member. To ensure the \c hostName line edit is
+ the first to receive input focus when this item is shown, we call
+ \l{QWidget::setFocus()}{setFocus()} immediately. This will not give the
+ widget focus right away; it will only prepare the item to automatically
+ receive focus once it is shown.
+
+ The QWidget based form is embedded into the proxy widget. The proxy is
+ hidden initially; we only want to show it when the pad is rotated at least
+ 90 degrees, and we also rotate the proxy itself by 180 degrees. This way we
+ give the impression that the proxy widget is "behind" the flipped pad, when
+ in fact, it's actually \e{on top of it}.
+
+ We enable \l{QGraphicsItem::ItemCoordinateCache}{ItemCoordinateCache} to
+ ensure the flip animation can run smoothly.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 4
+
+ We now create the selection item. This is simply another instance of \c
+ RoundRectItem that is slightly larger than the icons on the pad. We create
+ it as an immediate child of the \c FlippablePad, so the selection item is a
+ sibling to all the icons. By giving it a
+ \l{QGraphicsItem::zValue()}{Z-value} of 0.5 we ensure it will slide beteen
+ the pad and its icons.
+
+ What follows now is a series of animation initializations.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 5
+
+ We begin with the animations that apply to the splash item. The first
+ animation, \c smoothSplashMove, ensures that the "y" property of \c splash
+ will be animated with a 250-millisecond duration
+ \l{QEasingCurve::InQuad}{InQuad} easing function. \c smoothSplashOpacity
+ ensures the opacity of \c splash eases in and out in 250 milliseconds.
+
+ The values are assigned by \c PadNavigator's state machine, which is
+ created later.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 6
+
+ These are the animations that control the selection item's movement and the
+ \c xRotation and \c yRotation QGraphicsRotation objects that tilt the pad.
+ All animations have a duration of 125 milliseconds, and they all use the
+ \l{QEasingCurve::InOutQuad}{InOutQuad} easing function.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 7
+
+ We now create the animations that control the flip-effect when you press
+ the enter key. The main goal is to rotate the pad by 180 degrees or back,
+ but we also need to make sure the selection item's tilt rotations are reset
+ back to 0 when the pad is flipped, and restored back to their original
+ values when flipped back:
+
+ \list
+ \o \c smoothFlipRotation: Animates the main 180 degree rotation of the pad.
+ \o \c smoothFlipScale: Scales the pad out and then in again while the pad is rotating.
+ \o \c smoothFlipXRotation: Animates the selection item's X-tilt to 0 and back.
+ \o \c smoothFlipYRotation: Animates the selection item's Y-tilt to 0 and back.
+ \o \c flipAnimation: A parallel animation group that ensures all the above animations are run in parallel.
+ \endlist
+
+ All animations are given a 500 millisecond duration and an
+ \l{QEasingCurve::InOutQuad}{InOutQuad} easing function.
+
+ It's worth taking a close look at \c smoothFlipScale. This animation's
+ start and end values are both 1.0, but at animation step 0.5 the
+ animation's value is 0.7. This means that after 50% of the animation's
+ duration, or 250 milliseconds, the pad will be scaled down to 0.7x of its
+ original size, which gives a great visual effect while flipping.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 8
+
+ This section uses a trick to ensure that certain properties are assigned
+ precisely when the flip animation passes 50%, or 90 degrees, rotation. In
+ short, the pad's icons and selection item are all hidden, the pad's \c fill
+ property is enabled, and \c backItem is shown when flipping over. When
+ flipping back, the reverse properties are applied.
+
+ The way this is achieved is by running a sequential animation in parallel
+ to the other animations. This sequence, dubbed \c setVariablesSequence,
+ starts with a 250 millisecond pause, and then executes several animations
+ with a duration of 0. Each animation will ensure that properties are set
+ immediate at this point.
+
+ This approach can also be used to call functions or set any other
+ properties at a specific time while an animation is running.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 9
+
+ We will now create the state machine. The whole \c PadNavigator state
+ machinery is controlled by one single state machine that has a
+ straight-forward state structure. The state engine itself is created
+ as a child of the \c PadNavigator itself. We then create three top level
+ states:
+
+ \list
+ \o \c splashState: The initial state where the splash item is visible.
+ \o \c frontState: The base state where the splash is gone and we can see
+ the front side of the pad, and navigate the selection item.
+ \o \c backState: The flipped state where the \c backItem is visible, and we
+ can interact with the QGraphicsProxyWidget-embedded form.
+ \endlist
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 10
+
+ Each state assigns specific properties to objects on entry. Most
+ interesting perhaps is the assignment of the value 0.0 to the pad's \c
+ flipRotation angle property when in \c frontState, and 180.0 when in \c
+ backState. At the end of this section we register default animations with
+ the state engine; these animations will apply to their respective objects
+ and properties for any state transition. Otherwise it's common to assign
+ animations to specific transitions.
+
+ The \c splashState state is set as the initial state. This is required
+ before we start the state engine. We proceed with creating some
+ transitions.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 11
+
+ QEventTransition defines a very flexible transition type. You can use this
+ class to trigger a transition based on an object receiving an event of a
+ specific type. In this case, we would like to transition from \c
+ splashState into \c frontState if \c PadNavigator receives any key press
+ event (QEvent::KeyPress).
+
+ We register the \c splashItem's animations to this transition to ensure they
+ are used to animate the item's movement and opacity.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 12
+
+ We use QKeyEventTransition to capture specific key events. In this case, we
+ detect that the user presses Qt::Key_Return or Qt::Key_Enter, and use this
+ to trigger transitions between \c frontState and backState. We register \c
+ flipAnimation, our complex parallel animation group, with these
+ transitions.
+
+ We continue by defining the states for each of the icons in the grid.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 13
+
+ We will use state groups to control transitions between icons. Each icon
+ represents a \e substate of \c frontState. We will then define transitions
+ between the states by detecting key presses, using QKeyEventTransition.
+
+ We start by creating all the substates, and at the same time we create a
+ temporary grid structure for the states to make it easier to find which
+ states represents icons that are up, down, left and to the right each
+ other.
+
+ Once the first substate is known, we set this up as the initial substate of
+ \c frontState. We will use the (0, 0), or top-left, icon for the initial
+ substate. We initialze the selection item's position to be exactly where
+ the top-left icon is.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 14
+
+ We can now create four transitions for each icon. Each transition ensures
+ that we move to the state corresponding to which arrow key has been
+ pressed. It's clear from this techinique that we could design any other
+ specific transitions to and from each of the sub states depending on these
+ and other keys.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 15
+
+ Also, for each of the icons, we assign suitable values to the \c xRotation
+ and \c yRotation objects' "angle"-properties. If you recall, these
+ properties "tilt" the pad corresponding to which item is currently
+ selected. We ensure each icon is invisible when the pad is flipped, and
+ visible when the pad is not flipped. To ensure the visible property is
+ assigned at the right time, we add property-controlling animations to the
+ \c setVariableSequence animation defined earlier.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 16
+
+ We are now finished with all states, transitions, and animations. We now
+ create the scene that will contain all our items. The scene gets a defined
+ background pixmap, and we disable item indexing (as most items in this
+ scene are animated). We add our \c pad item to the scene, and use its
+ bounding rectangle to fixate the scene rectangle. This rectangle is used by
+ the view to find a suitable size for the application window.
+
+ Then the scene is assigned to the view, or in our case, \c PadNavigator
+ itself.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 17
+
+ Now that the scene has received its final size, we can position the splash
+ item at the very top, find its fade-out position, and add it to the scene.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 18
+
+ The view toggles a few necessary properties:
+
+ \list
+ \o It disables its scroll bars - this application has no use for scroll bars.
+ \o It assigns a minimum size. This is necessary to avoid numerical errors
+ in our fit-in-view \c resizeEvent() implementation.
+ \o It sets \l{QGraphicsView::FullViewportUpdate}{FullViewportUpdate}, to
+ ensure QGraphicsView doesn't spend time figuring out precisely what needs
+ to be redrawn. This application is very simple - if anything changes,
+ everything is updated.
+ \o It enables background caching - this makes no performance difference
+ with OpenGL, but without OpenGL it avoids unnecessary re-scaling of the
+ background pixmap.
+ \o It sets render hints that increase rendering quality.
+ \o If OpenGL is supported, a QGLWidget viewport is assigned to the view.
+ \endlist
+
+ Finally, we start the state engine.
+
+ \snippet examples/graphicsview/padnavigator/padnavigator.cpp 19
+
+ The \l{QGraphicsView::resizeEvent()}{resizeEvent()} implementation calls
+ the base implementation, and then calls QGraphicsView::fitInView() to scale
+ the scene so that it fits perfectly inside the view.
+
+ By resizing the main application window, you can see this effect yourself.
+ The scene contents grow when you make the window larger, and shrink when
+ you make it smaller, while keeping the aspect ratio intact.
+
+ \section1 The main() Function
+
+ \snippet examples/graphicsview/padnavigator/main.cpp 0
+
+ The \c main function creates the QApplication instance, uses
+ Q_INIT_RESOURCE to ensure our compiled-in resources aren't removed by the
+ linker, and then creates a 3x3 \c PadNavigator instance and shows it.
+
+ Our flippable pad shows up with a suitable splash item once control returns
+ to the event loop.
+
+ \section1 Performance Notes
+
+ The example uses OpenGL if this is available, to achieve optimal
+ performance; otherwise perspective tranformations can be quite costly.
+
+ Although this example does use QGraphicsProxyWidget to demonstrate
+ integration of Qt widget components integrated into Graphics View, using
+ QGraphicsProxyWidget comes with a performance penalty, and is therefore not
+ recommended for embedded development.
+
+ This example uses extensive item caching to avoid rerendering of static
+ elements, at the expense of graphics memory.
*/
diff --git a/doc/src/getting-started/examples.qdoc b/doc/src/getting-started/examples.qdoc
index 542f672..f511cd6 100644
--- a/doc/src/getting-started/examples.qdoc
+++ b/doc/src/getting-started/examples.qdoc
@@ -651,6 +651,7 @@
\o \l{graphicsview/diagramscene}{Diagram Scene}\raisedaster
\o \l{graphicsview/dragdroprobot}{Drag and Drop Robot}\raisedaster
\o \l{graphicsview/elasticnodes}{Elastic Nodes}\raisedaster
+ \o \l{graphicsview/padnavigator}{Pad Navigator}\raisedaster
\o \l{graphicsview/portedasteroids}{Ported Asteroids}
\o \l{graphicsview/portedcanvas}{Ported Canvas}
\endlist