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diff --git a/examples/widgets/doc/icons.qdoc b/examples/widgets/doc/icons.qdoc new file mode 100644 index 0000000000..2ccf8cac43 --- /dev/null +++ b/examples/widgets/doc/icons.qdoc @@ -0,0 +1,780 @@ +/**************************************************************************** +** +** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies). +** Contact: http://www.qt-project.org/ +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** GNU Free Documentation License +** 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. +** +** Other Usage +** Alternatively, this file may be used in accordance with the terms +** and conditions contained in a signed written agreement between you +** and Nokia. +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \example widgets/icons + \title Icons Example + + The Icons example shows how QIcon can generate pixmaps reflecting + an icon's state, mode and size. These pixmaps are generated from + the set of pixmaps made available to the icon, and are used by Qt + widgets to show an icon representing a particular action. + + \image icons-example.png Screenshot of the Icons example + + Contents: + + \tableofcontents + + \section1 QIcon Overview + + The QIcon class provides scalable icons in different modes and + states. An icon's state and mode are depending on the intended use + of the icon. Qt currently defines four modes: + + \table + \header \li Mode \li Description + \row + \li QIcon::Normal + \li Display the pixmap when the user is not interacting with the + icon, but the functionality represented by the icon is + available. + \row + \li QIcon::Active + \li Display the pixmap when the functionality represented by the + icon is available and the user is interacting with the icon, + for example, moving the mouse over it or clicking it. + \row + \li QIcon::Disabled + \li Display the pixmap when the functionality represented by + the icon is not available. + \row + \li QIcon::Selected + \li Display the pixmap when the icon is selected. + \endtable + + QIcon's states are QIcon::On and QIcon::Off, which will display + the pixmap when the widget is in the respective state. The most + common usage of QIcon's states are when displaying checkable tool + buttons or menu entries (see QAbstractButton::setCheckable() and + QAction::setCheckable()). When a tool button or menu entry is + checked, the QIcon's state is \l{QIcon::}{On}, otherwise it's + \l{QIcon::}{Off}. You can, for example, use the QIcon's states to + display differing pixmaps depending on whether the tool button or + menu entry is checked or not. + + A QIcon can generate smaller, larger, active, disabled, and + selected pixmaps from the set of pixmaps it is given. Such + pixmaps are used by Qt widgets to show an icon representing a + particular action. + + \section1 Overview of the Icons Application + + With the Icons application you get a preview of an icon's + generated pixmaps reflecting its different states, modes and size. + + When an image is loaded into the application, it is converted into + a pixmap and becomes a part of the set of pixmaps available to the + icon. An image can be excluded from this set by checking off the + related checkbox. The application provides a sub directory + containing sets of images explicitly designed to illustrate how Qt + renders an icon in different modes and states. + + The application allows you to manipulate the icon size with some + predefined sizes and a spin box. The predefined sizes are style + dependent, but most of the styles have the same values: Only the + Macintosh style differ by using 32 pixels, instead of 16 pixels, + for toolbar buttons. You can navigate between the available styles + using the \uicontrol View menu. + + \image icons-view-menu.png Screenshot of the View menu + + The \uicontrol View menu also provide the option to make the application + guess the icon state and mode from an image's file name. The \uicontrol + File menu provide the options of adding an image and removing all + images. These last options are also available through a context + menu that appears if you press the right mouse button within the + table of image files. In addition, the \uicontrol File menu provide an + \uicontrol Exit option, and the \uicontrol Help menu provide information about + the example and about Qt. + + \image icons_find_normal.png Screenshot of the Find Files + + The screenshot above shows the application with one image file + loaded. The \uicontrol {Guess Image Mode/State} is enabled and the + style is Plastique. + + When QIcon is provided with only one available pixmap, that + pixmap is used for all the states and modes. In this case the + pixmap's icon mode is set to normal, and the generated pixmaps + for the normal and active modes will look the same. But in + disabled and selected mode, Qt will generate a slightly different + pixmap. + + The next screenshot shows the application with an additional file + loaded, providing QIcon with two available pixmaps. Note that the + new image file's mode is set to disabled. When rendering the \uicontrol + Disabled mode pixmaps, Qt will now use the new image. We can see + the difference: The generated disabled pixmap in the first + screenshot is slightly darker than the pixmap with the originally + set disabled mode in the second screenshot. + + \image icons_find_normal_disabled.png Screenshot of the Find Files + + When Qt renders the icon's pixmaps it searches through the set of + available pixmaps following a particular algorithm. The algorithm + is documented in QIcon, but we will describe some particular cases + below. + + \image icons_monkey_active.png Screenshot of the Find Files + + In the screenshot above, we have set \c monkey_on_32x32 to be an + Active/On pixmap and \c monkey_off_64x64 to be Normal/Off. To + render the other six mode/state combinations, QIcon uses the + search algorithm described in the table below: + + \table 100% + \header \li{2,1} Requested Pixmap \li {8,1} Preferred Alternatives (mode/state) + \header \li Mode \li State \li 1 \li 2 \li 3 \li 4 \li 5 \li 6 \li 7 \li 8 + \row \li{1,2} Normal \li Off \li \b N0 \li A0 \li N1 \li A1 \li D0 \li S0 \li D1 \li S1 + \row \li On \li N1 \li \b A1 \li N0 \li A0 \li D1 \li S1 \li D0 \li S0 + \row \li{1,2} Active \li Off \li A0 \li \b N0 \li A1 \li N1 \li D0 \li S0 \li D1 \li S1 + \row \li On \li \b A1 \li N1 \li A0 \li N0 \li D1 \li S1 \li D0 \li S0 + \row \li{1,2} Disabled \li Off \li D0 \li \b {N0'} \li A0' \li D1 \li N1' \li A1' \li S0' \li S1' + \row \li On \li D1 \li N1' \li \b {A1'} \li D0 \li N0' \li A0' \li S1' \li S0' + \row \li{1,2} Selected \li Off \li S0 \li \b {N0''} \li A0'' \li S1 \li N1'' \li A1'' \li D0'' \li D1'' + \row \li On \li S1 \li N1'' \li \b {A1''} \li S0 \li N0'' \li A0'' \li D1'' \li D0'' + \endtable + + In the table, "0" and "1" stand for Off" and "On", respectively. + Single quotes indicates that QIcon generates a disabled ("grayed + out") version of the pixmap; similarly, double quuote indicate + that QIcon generates a selected ("blued out") version of the + pixmap. + + The alternatives used in the screenshot above are shown in bold. + For example, the Disabled/Off pixmap is derived by graying out + the Normal/Off pixmap (\c monkey_off_64x64). + + In the next screenshots, we loaded the whole set of monkey + images. By checking or unchecking file names from the image list, + we get different results: + + \table + \row + \li \inlineimage icons_monkey.png Screenshot of the Monkey Files + \li \inlineimage icons_monkey_mess.png Screenshot of the Monkey Files + \endtable + + For any given mode/state combination, it is possible to specify + several images at different resolutions. When rendering an + icon, QIcon will automatically pick the most suitable image + and scale it down if necessary. (QIcon never scales up images, + because this rarely looks good.) + + The screenshots below shows what happens when we provide QIcon + with three images (\c qt_extended_16x16.png, \c qt_extended_32x32.png, \c + qt_extended_48x48.png) and try to render the QIcon at various + resolutions: + + \table + \row + \li + \li \inlineimage icons_qt_extended_8x8.png Qt Extended icon at 8 x 8 + \li \inlineimage icons_qt_extended_16x16.png Qt Extended icon at 16 x 16 + \li \inlineimage icons_qt_extended_17x17.png Qt Extended icon at 17 x 17 + \row + \li + \li 8 x 8 + \li \b {16 x 16} + \li 17 x 17 + \row + \li \inlineimage icons_qt_extended_32x32.png Qt Extended icon at 32 x 32 + \li \inlineimage icons_qt_extended_33x33.png Qt Extended icon at 33 x 33 + \li \inlineimage icons_qt_extended_48x48.png Qt Extended icon at 48 x 48 + \li \inlineimage icons_qt_extended_64x64.png Qt Extended icon at 64 x 64 + \row + \li \b {32 x 32} + \li 33 x 33 + \li \b {48 x 48} + \li 64 x 64 + \endtable + + For sizes up to 16 x 16, QIcon uses \c qt_extended_16x16.png and + scales it down if necessary. For sizes between 17 x 17 and 32 x + 32, it uses \c qt_extended_32x32.png. For sizes above 32 x 32, it uses + \c qt_extended_48x48.png. + + \section1 Line-by-Line Walkthrough + + The Icons example consists of four classes: + + \list + \li \c MainWindow inherits QMainWindow and is the main application + window. + \li \c IconPreviewArea is a custom widget that displays all + combinations of states and modes for a given icon. + \li \c IconSizeSpinBox is a subclass of QSpinBox that lets the + user enter icon sizes (e.g., "48 x 48"). + \li \c ImageDelegate is a subclass of QItemDelegate that provides + comboboxes for letting the user set the mode and state + associated with an image. + \endlist + + We will start by reviewing the \c IconPreviewArea class before we + take a look at the \c MainWindow class. Finally, we will review the + \c IconSizeSpinBox and \c ImageDelegate classes. + + \section2 IconPreviewArea Class Definition + + An \c IconPreviewArea widget consists of a group box containing a grid of + QLabel widgets displaying headers and pixmaps. + + \image icons_preview_area.png Screenshot of IconPreviewArea. + + \snippet widgets/icons/iconpreviewarea.h 0 + + The \c IconPreviewArea class inherits QWidget. It displays the + generated pixmaps corresponding to an icon's possible states and + modes at a given size. + + We need two public functions to set the current icon and the + icon's size. In addition the class has three private functions: We + use the \c createHeaderLabel() and \c createPixmapLabel() + functions when constructing the preview area, and we need the \c + updatePixmapLabels() function to update the preview area when + the icon or the icon's size has changed. + + The \c NumModes and \c NumStates constants reflect \l{QIcon}'s + number of currently defined modes and states. + + \section2 IconPreviewArea Class Implementation + + \snippet widgets/icons/iconpreviewarea.cpp 0 + + In the constructor we create the labels displaying the headers and + the icon's generated pixmaps, and add them to a grid layout. + + When creating the header labels, we make sure the enums \c + NumModes and \c NumStates defined in the \c .h file, correspond + with the number of labels that we create. Then if the enums at + some point are changed, the \c Q_ASSERT() macro will alert that this + part of the \c .cpp file needs to be updated as well. + + If the application is built in debug mode, the \c Q_ASSERT() + macro will expand to + + \snippet doc/src/snippets/code/doc_src_examples_icons.cpp 0 + + In release mode, the macro simply disappear. The mode can be set + in the application's \c .pro file. One way to do so is to add an + option to \c qmake when building the application: + + \snippet doc/src/snippets/code/doc_src_examples_icons.qdoc 1 + + or + + \snippet doc/src/snippets/code/doc_src_examples_icons.qdoc 2 + + Another approach is to add this line directly to the \c .pro + file. + + \snippet widgets/icons/iconpreviewarea.cpp 1 + \codeline + \snippet widgets/icons/iconpreviewarea.cpp 2 + + The public \c setIcon() and \c setSize() functions change the icon + or the icon size, and make sure that the generated pixmaps are + updated. + + \snippet widgets/icons/iconpreviewarea.cpp 3 + \codeline + \snippet widgets/icons/iconpreviewarea.cpp 4 + + We use the \c createHeaderLabel() and \c createPixmapLabel() + functions to create the preview area's labels displaying the + headers and the icon's generated pixmaps. Both functions return + the QLabel that is created. + + \snippet widgets/icons/iconpreviewarea.cpp 5 + + We use the private \c updatePixmapLabel() function to update the + generated pixmaps displayed in the preview area. + + For each mode, and for each state, we retrieve a pixmap using the + QIcon::pixmap() function, which generates a pixmap corresponding + to the given state, mode and size. + + \section2 MainWindow Class Definition + + The \c MainWindow widget consists of three main elements: an + images group box, an icon size group box and a preview area. + + \image icons-example.png Screenshot of the Icons example + + \snippet widgets/icons/mainwindow.h 0 + + The MainWindow class inherits from QMainWindow. We reimplement the + constructor, and declare several private slots: + + \list + \li The \c about() slot simply provides information about the example. + \li The \c changeStyle() slot changes the application's GUI style and + adjust the style dependent size options. + \li The \c changeSize() slot changes the size of the preview area's icon. + \li The \c changeIcon() slot updates the set of pixmaps available to the + icon displayed in the preview area. + \li The \c addImage() slot allows the user to load a new image into the + application. + \endlist + + In addition we declare several private functions to simplify the + constructor. + + \section2 MainWindow Class Implementation + + \snippet widgets/icons/mainwindow.cpp 0 + + In the constructor we first create the main window's central + widget and its child widgets, and put them in a grid layout. Then + we create the menus with their associated entries and actions. + + Before we resize the application window to a suitable size, we set + the window title and determine the current style for the + application. We also enable the icon size spin box by clicking the + associated radio button, making the current value of the spin box + the icon's initial size. + + \snippet widgets/icons/mainwindow.cpp 1 + + The \c about() slot displays a message box using the static + QMessageBox::about() function. In this example it displays a + simple box with information about the example. + + The \c about() function looks for a suitable icon in four + locations: It prefers its parent's icon if that exists. If it + doesn't, the function tries the top-level widget containing + parent, and if that fails, it tries the active window. As a last + resort it uses the QMessageBox's Information icon. + + \snippet widgets/icons/mainwindow.cpp 2 + + In the \c changeStyle() slot we first check the slot's + parameter. If it is false we immediately return, otherwise we find + out which style to change to, i.e. which action that triggered the + slot, using the QObject::sender() function. + + This function returns the sender as a QObject pointer. Since we + know that the sender is a QAction object, we can safely cast the + QObject. We could have used a C-style cast or a C++ \c + static_cast(), but as a defensive programming technique we use a + \l qobject_cast(). The advantage is that if the object has the + wrong type, a null pointer is returned. Crashes due to null + pointers are much easier to diagnose than crashes due to unsafe + casts. + + \snippet widgets/icons/mainwindow.cpp 3 + \snippet widgets/icons/mainwindow.cpp 4 + + Once we have the action, we extract the style name using + QAction::data(). Then we create a QStyle object using the static + QStyleFactory::create() function. + + Although we can assume that the style is supported by the + QStyleFactory: To be on the safe side, we use the \c Q_ASSERT() + macro to check if the created style is valid before we use the + QApplication::setStyle() function to set the application's GUI + style to the new style. QApplication will automatically delete + the style object when a new style is set or when the application + exits. + + The predefined icon size options provided in the application are + style dependent, so we need to update the labels in the icon size + group box and in the end call the \c changeSize() slot to update + the icon's size. + + \snippet widgets/icons/mainwindow.cpp 5 + + The \c changeSize() slot sets the size for the preview area's + icon. + + To determine the new size we first check if the spin box is + enabled. If it is, we extract the extent of the new size from the + box. If it's not, we search through the predefined size options, + extract the QStyle::PixelMetric and use the QStyle::pixelMetric() + function to determine the extent. Then we create a QSize object + based on the extent, and use that object to set the size of the + preview area's icon. + + \snippet widgets/icons/mainwindow.cpp 12 + + The first thing we do when the \c addImage() slot is called, is to + show a file dialog to the user. The easiest way to create a file + dialog is to use QFileDialog's static functions. Here we use the + \l {QFileDialog::getOpenFileNames()}{getOpenFileNames()} function + that will return one or more existing files selected by the user. + + For each of the files the file dialog returns, we add a row to the + table widget. The table widget is listing the images the user has + loaded into the application. + + \snippet widgets/icons/mainwindow.cpp 13 + \snippet widgets/icons/mainwindow.cpp 14 + + We retrieve the image name using the QFileInfo::baseName() + function that returns the base name of the file without the path, + and create the first table widget item in the row. Then we add the + file's complete name to the item's data. Since an item can hold + several information pieces, we need to assign the file name a role + that will distinguish it from other data. This role can be Qt::UserRole + or any value above it. + + We also make sure that the item is not editable by removing the + Qt::ItemIsEditable flag. Table items are editable by default. + + \snippet widgets/icons/mainwindow.cpp 15 + \snippet widgets/icons/mainwindow.cpp 16 + \snippet widgets/icons/mainwindow.cpp 17 + + Then we create the second and third items in the row making the + default mode Normal and the default state Off. But if the \uicontrol + {Guess Image Mode/State} option is checked, and the file name + contains "_act", "_dis", or "_sel", the modes are changed to + Active, Disabled, or Selected. And if the file name contains + "_on", the state is changed to On. The sample files in the + example's \c images subdirectory respect this naming convension. + + \snippet widgets/icons/mainwindow.cpp 18 + \snippet widgets/icons/mainwindow.cpp 19 + + In the end we add the items to the associated row, and use the + QTableWidget::openPersistentEditor() function to create + comboboxes for the mode and state columns of the items. + + Due to the connection between the table widget's \l + {QTableWidget::itemChanged()}{itemChanged()} signal and the \c + changeIcon() slot, the new image is automatically converted into a + pixmap and made part of the set of pixmaps available to the icon + in the preview area. So, corresponding to this fact, we need to + make sure that the new image's check box is enabled. + + \snippet widgets/icons/mainwindow.cpp 6 + \snippet widgets/icons/mainwindow.cpp 7 + + The \c changeIcon() slot is called when the user alters the set + of images listed in the QTableWidget, to update the QIcon object + rendered by the \c IconPreviewArea. + + We first create a QIcon object, and then we run through the + QTableWidget, which lists the images the user has loaded into the + application. + + \snippet widgets/icons/mainwindow.cpp 8 + \snippet widgets/icons/mainwindow.cpp 9 + \snippet widgets/icons/mainwindow.cpp 10 + + We also extract the image file's name using the + QTableWidgetItem::data() function. This function takes a + Qt::DataItemRole as an argument to retrieve the right data + (remember that an item can hold several pieces of information) + and returns it as a QVariant. Then we use the + QVariant::toString() function to get the file name as a QString. + + To create a pixmap from the file, we need to first create an + image and then convert this image into a pixmap using + QPixmap::fromImage(). Once we have the final pixmap, we add it, + with its associated mode and state, to the QIcon's set of + available pixmaps. + + \snippet widgets/icons/mainwindow.cpp 11 + + After running through the entire list of images, we change the + icon of the preview area to the one we just created. + + \snippet widgets/icons/mainwindow.cpp 20 + + In the \c removeAllImages() slot, we simply set the table widget's + row count to zero, automatically removing all the images the user + has loaded into the application. Then we update the set of pixmaps + available to the preview area's icon using the \c changeIcon() + slot. + + \image icons_images_groupbox.png Screenshot of the images group box + + The \c createImagesGroupBox() function is implemented to simplify + the constructor. The main purpose of the function is to create a + QTableWidget that will keep track of the images the user has + loaded into the application. + + \snippet widgets/icons/mainwindow.cpp 21 + + First we create a group box that will contain the table widget. + Then we create a QTableWidget and customize it to suit our + purposes. + + We call QAbstractItemView::setSelectionMode() to prevent the user + from selecting items. + + The QAbstractItemView::setItemDelegate() call sets the item + delegate for the table widget. We create a \c ImageDelegate that + we make the item delegate for our view. + + The QItemDelegate class can be used to provide an editor for an item view + class that is subclassed from QAbstractItemView. Using a delegate + for this purpose allows the editing mechanism to be customized and + developed independently from the model and view. + + In this example we derive \c ImageDelegate from QItemDelegate. + QItemDelegate usually provides line editors, while our subclass + \c ImageDelegate, provides comboboxes for the mode and state + fields. + + \snippet widgets/icons/mainwindow.cpp 22 + \snippet widgets/icons/mainwindow.cpp 23 + + Then we customize the QTableWidget's horizontal header, and hide + the vertical header. + + \snippet widgets/icons/mainwindow.cpp 24 + \snippet widgets/icons/mainwindow.cpp 25 + + At the end, we connect the QTableWidget::itemChanged() signal to + the \c changeIcon() slot to ensuret that the preview area is in + sync with the image table. + + \image icons_size_groupbox.png Screenshot of the icon size group box + + The \c createIconSizeGroupBox() function is called from the + constructor. It creates the widgets controlling the size of the + preview area's icon. + + \snippet widgets/icons/mainwindow.cpp 26 + + First we create a group box that will contain all the widgets; + then we create the radio buttons and the spin box. + + The spin box is not a regular QSpinBox but an \c IconSizeSpinBox. + The \c IconSizeSpinBox class inherits QSpinBox and reimplements + two functions: QSpinBox::textFromValue() and + QSpinBox::valueFromText(). The \c IconSizeSpinBox is designed to + handle icon sizes, e.g., "32 x 32", instead of plain integer + values. + + \snippet widgets/icons/mainwindow.cpp 27 + + Then we connect all of the radio buttons + \l{QRadioButton::toggled()}{toggled()} signals and the spin box's + \l {QSpinBox::valueChanged()}{valueChanged()} signal to the \c + changeSize() slot to make sure that the size of the preview + area's icon is updated whenever the user changes the icon size. + In the end we put the widgets in a layout that we install on the + group box. + + \snippet widgets/icons/mainwindow.cpp 28 + + In the \c createActions() function we create and customize all the + actions needed to implement the functionality associated with the + menu entries in the application. + + In particular we create the \c styleActionGroup based on the + currently available GUI styles using + QStyleFactory. QStyleFactory::keys() returns a list of valid keys, + typically including "windows", "motif", "cde", and + "plastique". Depending on the platform, "windowsxp" and + "macintosh" may be available. + + We create one action for each key, and adds the action to the + action group. Also, for each action, we call QAction::setData() + with the style name. We will retrieve it later using + QAction::data(). + + \snippet widgets/icons/mainwindow.cpp 29 + + In the \c createMenu() function, we add the previously created + actions to the \uicontrol File, \uicontrol View and \uicontrol Help menus. + + The QMenu class provides a menu widget for use in menu bars, + context menus, and other popup menus. We put each menu in the + application's menu bar, which we retrieve using + QMainWindow::menuBar(). + + \snippet widgets/icons/mainwindow.cpp 30 + + QWidgets have a \l{QWidget::contextMenuPolicy}{contextMenuPolicy} + property that controls how the widget should behave when the user + requests a context menu (e.g., by right-clicking). We set the + QTableWidget's context menu policy to Qt::ActionsContextMenu, + meaning that the \l{QAction}s associated with the widget should + appear in its context menu. + + Then we add the \uicontrol{Add Image} and \uicontrol{Remove All Images} + actions to the table widget. They will then appear in the table + widget's context menu. + + \snippet widgets/icons/mainwindow.cpp 31 + + In the \c checkCurrentStyle() function we go through the group of + style actions, looking for the current GUI style. + + For each action, we first extract the style name using + QAction::data(). Since this is only a QStyleFactory key (e.g., + "macintosh"), we cannot compare it directly to the current + style's class name. We need to create a QStyle object using the + static QStyleFactory::create() function and compare the class + name of the created QStyle object with that of the current style. + As soon as we are done with a QStyle candidate, we delete it. + + For all QObject subclasses that use the \c Q_OBJECT macro, the + class name of an object is available through its + \l{QObject::metaObject()}{meta-object}. + + We can assume that the style is supported by + QStyleFactory, but to be on the safe side we use the \c + Q_ASSERT() macro to make sure that QStyleFactory::create() + returned a valid pointer. + + \section2 IconSizeSpinBox Class Definition + + \snippet widgets/icons/iconsizespinbox.h 0 + + The \c IconSizeSpinBox class is a subclass of QSpinBox. A plain + QSpinBox can only handle integers. But since we want to display + the spin box's values in a more sophisticated way, we need to + subclass QSpinBox and reimplement the QSpinBox::textFromValue() + and QSpinBox::valueFromText() functions. + + \image icons_size_spinbox.png Screenshot of the icon size spinbox + + \section2 IconSizeSpinBox Class Implementation + + \snippet widgets/icons/iconsizespinbox.cpp 0 + + The constructor is trivial. + + \snippet widgets/icons/iconsizespinbox.cpp 2 + + QSpinBox::textFromValue() is used by the spin box whenever it + needs to display a value. The default implementation returns a + base 10 representation of the \c value parameter. + + Our reimplementation returns a QString of the form "32 x 32". + + \snippet widgets/icons/iconsizespinbox.cpp 1 + + The QSpinBox::valueFromText() function is used by the spin box + whenever it needs to interpret text typed in by the user. Since + we reimplement the \c textFromValue() function we also need to + reimplement the \c valueFromText() function to interpret the + parameter text and return the associated int value. + + We parse the text using a regular expression (a QRegExp). We + define an expression that matches one or several digits, + optionally followed by whitespace, an "x" or the times symbol, + whitespace and one or several digits again. + + The first digits of the regular expression are captured using + parentheses. This enables us to use the QRegExp::cap() or + QRegExp::capturedTexts() functions to extract the matched + characters. If the first and second numbers of the spin box value + differ (e.g., "16 x 24"), we use the first number. + + When the user presses \uicontrol Enter, QSpinBox first calls + QSpinBox::valueFromText() to interpret the text typed by the + user, then QSpinBox::textFromValue() to present it in a canonical + format (e.g., "16 x 16"). + + \section2 ImageDelegate Class Definition + + \snippet widgets/icons/imagedelegate.h 0 + + The \c ImageDelegate class is a subclass of QItemDelegate. The + QItemDelegate class provides display and editing facilities for + data items from a model. A single QItemDelegate object is + responsible for all items displayed in a item view (in our case, + a QTableWidget). + + A QItemDelegate can be used to provide an editor for an item view + class that is subclassed from QAbstractItemView. Using a delegate + for this purpose allows the editing mechanism to be customized and + developed independently from the model and view. + + \snippet widgets/icons/imagedelegate.h 1 + + The default implementation of QItemDelegate creates a QLineEdit. + Since we want the editor to be a QComboBox, we need to subclass + QItemDelegate and reimplement the QItemDelegate::createEditor(), + QItemDelegate::setEditorData() and QItemDelegate::setModelData() + functions. + + \snippet widgets/icons/imagedelegate.h 2 + + The \c emitCommitData() slot is used to emit the + QImageDelegate::commitData() signal with the appropriate + argument. + + \section2 ImageDelegate Class Implementation + + \snippet widgets/icons/imagedelegate.cpp 0 + + The constructor is trivial. + + \snippet widgets/icons/imagedelegate.cpp 1 + + The default QItemDelegate::createEditor() implementation returns + the widget used to edit the item specified by the model and item + index for editing. The parent widget and style option are used to + control the appearance of the editor widget. + + Our reimplementation create and populate a combobox instead of + the default line edit. The contents of the combobox depends on + the column in the table for which the editor is requested. Column + 1 contains the QIcon modes, whereas column 2 contains the QIcon + states. + + In addition, we connect the combobox's \l + {QComboBox::activated()}{activated()} signal to the \c + emitCommitData() slot to emit the + QAbstractItemDelegate::commitData() signal whenever the user + chooses an item using the combobox. This ensures that the rest of + the application notices the change and updates itself. + + \snippet widgets/icons/imagedelegate.cpp 2 + + The QItemDelegate::setEditorData() function is used by + QTableWidget to transfer data from a QTableWidgetItem to the + editor. The data is stored as a string; we use + QComboBox::findText() to locate it in the combobox. + + Delegates work in terms of models, not items. This makes it + possible to use them with any item view class (e.g., QListView, + QListWidget, QTreeView, etc.). The transition between model and + items is done implicitly by QTableWidget; we don't need to worry + about it. + + \snippet widgets/icons/imagedelegate.cpp 3 + + The QItemDelegate::setEditorData() function is used by QTableWidget + to transfer data back from the editor to the \l{QTableWidgetItem}. + + \snippet widgets/icons/imagedelegate.cpp 4 + + The \c emitCommitData() slot simply emit the + QAbstractItemDelegate::commitData() signal for the editor that + triggered the slot. This signal must be emitted when the editor + widget has completed editing the data, and wants to write it back + into the model. +*/ |