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diff --git a/examples/widgets/doc/src/padnavigator.qdoc b/examples/widgets/doc/src/padnavigator.qdoc deleted file mode 100644 index 31440b650f..0000000000 --- a/examples/widgets/doc/src/padnavigator.qdoc +++ /dev/null @@ -1,586 +0,0 @@ -/**************************************************************************** -** -** Copyright (C) 2016 The Qt Company Ltd. -** Contact: https://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 https://www.qt.io/terms-conditions. For further -** information use the contact form at https://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: https://www.gnu.org/licenses/fdl-1.3.html. -** $QT_END_LICENSE$ -** -****************************************************************************/ - -/*! - \example graphicsview/padnavigator - \title Pad Navigator Example - \ingroup examples-graphicsview - \brief Demonstrates how to create animated user interface. - - The Pad Navigator Example shows how you can use Graphics View together with - embedded widgets and Qt's \l{The State Machine Framework}{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 display 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 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 graphicsview/padnavigator/roundrectitem.h 1 - - The private data members are: - - \list - \li \c pix: The optional pixmap that is drawn on top of the rectangle. - \li \c fillRect: Corresponds to the \c fill property. - \li \c color: The configurable gradient color fill of the rectangle. - \li \c bounds: The bounds of the rectangle. - \li \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 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 particularly well with OpenGL and OpenGL ES. - - \snippet 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 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 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 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 current brush from QApplication::palette(). We assign a single - unit wide pen for the stroke, assign the brush, and then draw the - rectangle. - - \snippet 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 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 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 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 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 graphicsview/padnavigator/flippablepad.cpp 2 - - The \c FlippablePad constructor passes suitable bounds (using \c - boundsForSize()) and specific color to \c RoundRectItem's constructor. - - \snippet 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 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 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 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 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 graphicsview/padnavigator/splashitem.cpp 1 - - \c SplashItem's bounding rectangle is fixed at (400x175). - - \snippet 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 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 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 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 graphicsview/padnavigator/padnavigator.cpp 2 - - Now we construct the \c FlippablePad item, passing its column-row count to - its constructor. - - The pad is controlled by three transformations, and we create one - QGraphicsRotation object for each of these. - - \list - \li \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. - \li \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. - \li \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 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 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 between - the pad and its icons. - - What follows now is a series of animation initializations. - - \snippet 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 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 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. - - \list - \li \c smoothFlipRotation: Animates the main 180 degree rotation of the pad. - \li \c smoothFlipScale: Scales the pad out and then in again while the pad is rotating. - \li \c flipAnimation: A parallel animation group that ensures 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 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 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 - \li \c splashState: The initial state where the splash item is visible. - \li \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. - \li \c backState: The flipped state where the \c backItem is visible, and we - can interact with the QGraphicsProxyWidget-embedded form. - \endlist - - \snippet 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. - - Specifically, we use default animations to control the selection item's - movement and tilt rotations. The tilt rotations are set to 0 when the pad - is flipped, and restored back to their original values when flipped back. - - 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 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 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 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 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 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 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 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 graphicsview/padnavigator/padnavigator.cpp 18 - - The view toggles a few necessary properties: - - \list - \li It disables its scroll bars - this application has no use for scroll bars. - \li It assigns a minimum size. This is necessary to avoid numerical errors - in our fit-in-view \c resizeEvent() implementation. - \li 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. - \li It enables background caching - this makes no performance difference - with OpenGL, but without OpenGL it avoids unnecessary re-scaling of the - background pixmap. - \li It sets render hints that increase rendering quality. - \li If OpenGL is supported, a QOpenGLWidget viewport is assigned to the view. - \endlist - - Finally, we start the state engine. - - \snippet 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 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. -*/ |