QIcon Class | Qt GUI 6.7.0
Description: The QIcon class provides scalable icons in different modes and states.

- Qt 6.7
- Qt GUI
- C++ Classes
- QIcon
- Qt 6.7.0 Reference Documentation

# QIcon Class

The QIcon class provides scalable icons in different modes and states. More...

Header: | #include <QIcon>
CMake: | find_package(Qt6 REQUIRED COMPONENTS Gui) target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: | QT += gui

- List of all members, including inherited members
- Deprecated members
- QIcon is part of Painting Classes and Implicitly Shared Classes.

## Public Types

enum | Mode { Normal, Disabled, Active, Selected }
enum | State { Off, On }

## Public Functions

| QIcon()
| QIcon(const QPixmap &pixmap)
| QIcon(const QString &fileName)
| QIcon(QIconEngine *engine)
| QIcon(const QIcon &other)
| QIcon(QIcon &&other)
| ~QIcon()
QSize | actualSize(const QSize &size, QIcon::Mode mode = Normal, QIcon::State state = Off) const
void | addFile(const QString &fileName, const QSize &size = QSize(), QIcon::Mode mode = Normal, QIcon::State state = Off)
void | addPixmap(const QPixmap &pixmap, QIcon::Mode mode = Normal, QIcon::State state = Off)
QList<QSize> | availableSizes(QIcon::Mode mode = Normal, QIcon::State state = Off) const
qint64 | cacheKey() const
bool | isMask() const
bool | isNull() const
QString | name() const
void | paint(QPainter *painter, const QRect &rect, Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const
void | paint(QPainter *painter, int x, int y, int w, int h, Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap | pixmap(const QSize &size, QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap | pixmap(int w, int h, QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap | pixmap(int extent, QIcon::Mode mode = Normal, QIcon::State state = Off) const
QPixmap | pixmap(const QSize &size, qreal devicePixelRatio, QIcon::Mode mode = Normal, QIcon::State state = Off) const
void | setIsMask(bool isMask)
void | swap(QIcon &other)
QVariant | operator QVariant() const
QIcon & | operator=(const QIcon &other)
QIcon & | operator=(QIcon &&other)

## Static Public Members

QStringList | fallbackSearchPaths()
QString | fallbackThemeName()
QIcon | fromTheme(const QString &name, const QIcon &fallback)
bool | hasThemeIcon(const QString &name)
void | setFallbackSearchPaths(const QStringList &paths)
void | setFallbackThemeName(const QString &name)
void | setThemeSearchPaths(const QStringList &paths)
QStringList | themeSearchPaths()

## Related Non-Members

QDataStream & | operator<<(QDataStream &stream, const QIcon &icon)
QDataStream & | operator>>(QDataStream &stream, QIcon &icon)

## Detailed Description

A QIcon can generate smaller, larger, active, and disabled pixmaps from the set of pixmaps it is given. Such pixmaps are used by Qt widgets to show an icon representing a particular action.

The simplest use of QIcon is to create one from a QPixmap file or resource, and then use it, allowing Qt to work out all the required icon styles and sizes. For example:

     QToolButton *button = new QToolButton;
     button->setIcon(QIcon("open.xpm"));

To undo a QIcon, simply set a null icon in its place:

     button->setIcon(QIcon());

Use the QImageReader::supportedImageFormats() and QImageWriter::supportedImageFormats() functions to retrieve a complete list of the supported file formats.

When you retrieve a pixmap using pixmap(QSize, Mode, State), and no pixmap for this given size, mode and state has been added with addFile() or addPixmap(), then QIcon will generate one on the fly. This pixmap generation happens in a QIconEngine. The default engine scales pixmaps down if required, but never up, and it uses the current style to calculate a disabled appearance. By using custom icon engines, you can customize every aspect of generated icons. With QIconEnginePlugin it is possible to register different icon engines for different file suffixes, making it possible for third parties to provide additional icon engines to those included with Qt.

Note: Since Qt 4.2, an icon engine that supports SVG is included.

### Making Classes that Use QIcon

If you write your own widgets that have an option to set a small pixmap, consider allowing a QIcon to be set for that pixmap. The Qt class QToolButton is an example of such a widget.

Provide a method to set a QIcon, and when you draw the icon, choose whichever pixmap is appropriate for the current state of your widget. For example:

     void MyWidget::drawIcon(QPainter *painter, QPoint pos)
     {
         QPixmap pixmap = icon.pixmap(QSize(22, 22),
                                        isEnabled() ? QIcon::Normal
                                                    : QIcon::Disabled,
                                        isChecked() ? QIcon::On
                                                    : QIcon::Off);
         painter->drawPixmap(pos, pixmap);
     }

You might also make use of the `Active` mode, perhaps making your widget `Active` when the mouse is over the widget (see QWidget::enterEvent()), while the mouse is pressed pending the release that will activate the function, or when it is the currently selected item. If the widget can be toggled, the "On" mode might be used to draw a different icon.

Note: QIcon needs a QGuiApplication instance before the icon is created.

### High DPI Icons

There are two ways that QIcon supports high DPI icons: via addFile() and fromTheme().

addFile() is useful if you have your own custom directory structure and do not need to use the freedesktop.org Icon Theme Specification. Icons created via this approach use Qt's "@nx" high DPI syntax.

Using fromTheme() is necessary if you plan on following the Icon Theme Specification. To make QIcon use the high DPI version of an image, add an additional entry to the appropriate `index.theme` file:

     [Icon Theme]
     Name=Test
     Comment=Test Theme

     Directories=32x32/actions,32x32@2/actions

     [32x32/actions]
     Size=32
     Context=Actions
     Type=Fixed

     # High DPI version of the entry above.
     [32x32@2/actions]
     Size=32
     Scale=2
     Type=Fixed

Your icon theme directory would then look something like this:

     ├── 32x32
     │   └── actions
     │       └── appointment-new.png
     ├── 32x32@2
     │   └── actions
     │       └── appointment-new.png
     └── index.theme

## Member Type Documentation

### enum QIcon::Mode

This enum type describes the mode for which a pixmap is intended to be used. The currently defined modes are:

Constant | Value | Description
--- | --- | ---
`QIcon::Normal` | `0` | Display the pixmap when the user is not interacting with the icon, but the functionality represented by the icon is available.
`QIcon::Disabled` | `1` | Display the pixmap when the functionality represented by the icon is not available.
`QIcon::Active` | `2` | 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.
`QIcon::Selected` | `3` | Display the pixmap when the item represented by the icon is selected.

### enum QIcon::State

This enum describes the state for which a pixmap is intended to be used. The state can be:

Constant | Value | Description
--- | --- | ---
`QIcon::Off` | `1` | Display the pixmap when the widget is in an "off" state
`QIcon::On` | `0` | Display the pixmap when the widget is in an "on" state

## Member Function Documentation

### `[noexcept]` QIcon::QIcon()

Constructs a null icon.

### QIcon::QIcon(const QPixmap &pixmap)

Constructs an icon from a pixmap.

### `[explicit]` QIcon::QIcon(const QString &fileName)

Constructs an icon from the file with the given fileName. The file will be loaded on demand.

If fileName contains a relative path (e.g. the filename only) the relevant file must be found relative to the runtime working directory.

The file name can refer to an actual file on disk or to one of the application's embedded resources. See the Resource System overview for details on how to embed images and other resource files in the application's executable.

Use the QImageReader::supportedImageFormats() and QImageWriter::supportedImageFormats() functions to retrieve a complete list of the supported file formats.

### `[explicit]` QIcon::QIcon(QIconEngine *engine)

Creates an icon with a specific icon engine. The icon takes ownership of the engine.

### QIcon::QIcon(const QIcon &other)

Constructs a copy of other. This is very fast.

### `[noexcept]` QIcon::QIcon(QIcon &&other)

Move-constructs a QIcon instance, making it point to the same object that other was pointing to.

### `[noexcept]` QIcon::~QIcon()

Destroys the icon.

### QSize QIcon::actualSize(const QSize &size, QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns the actual size of the icon for the requested size, mode, and state. The result might be smaller than requested, but never larger. The returned size is in device-independent pixels (This is relevant for high-dpi pixmaps.)

See also pixmap() and paint().

### void QIcon::addFile(const QString &fileName, const QSize &size = QSize(), QIcon::Mode mode = Normal, QIcon::State state = Off)

Adds an image from the file with the given fileName to the icon, as a specialization for size, mode and state. The file will be loaded on demand. Note: custom icon engines are free to ignore additionally added pixmaps.

If fileName contains a relative path (e.g. the filename only) the relevant file must be found relative to the runtime working directory.

The file name can refer to an actual file on disk or to one of the application's embedded resources. See the Resource System overview for details on how to embed images and other resource files in the application's executable.

Use the QImageReader::supportedImageFormats() and QImageWriter::supportedImageFormats() functions to retrieve a complete list of the supported file formats.

If a high resolution version of the image exists (identified by the suffix `@2x` on the base name), it is automatically loaded and added with the device pixel ratio set to a value of 2. This can be disabled by setting the environment variable `QT_HIGHDPI_DISABLE_2X_IMAGE_LOADING` (see QImageReader).

Note: When you add a non-empty filename to a QIcon, the icon becomes non-null, even if the file doesn't exist or points to a corrupt file.

See also addPixmap() and QPixmap::devicePixelRatio().

### void QIcon::addPixmap(const QPixmap &pixmap, QIcon::Mode mode = Normal, QIcon::State state = Off)

Adds pixmap to the icon, as a specialization for mode and state.

Custom icon engines are free to ignore additionally added pixmaps.

See also addFile().

### QList<QSize> QIcon::availableSizes(QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns a list of available icon sizes for the specified mode and state.

### qint64 QIcon::cacheKey() const

Returns a number that identifies the contents of this QIcon object. Distinct QIcon objects can have the same key if they refer to the same contents.

The cacheKey() will change when the icon is altered via addPixmap() or addFile().

Cache keys are mostly useful in conjunction with caching.

See also QPixmap::cacheKey().

### `[static]` QStringList QIcon::fallbackSearchPaths()

Returns the fallback search paths for icons.

The fallback search paths are consulted for standalone icon files if the current icon theme or fallback icon theme do not provide results for an icon lookup.

If not set, the fallback search paths will be defined by the platform.

See also setFallbackSearchPaths() and themeSearchPaths().

### `[static]` QString QIcon::fallbackThemeName()

Returns the name of the fallback icon theme.

If not set, the fallback icon theme will be defined by the platform.

Note: Platform fallback icon themes are only implemented on Freedesktop based systems at the moment, and the icon theme depends on your desktop settings.

See also setFallbackThemeName() and themeName().

### `[static]` QIcon QIcon::fromTheme(const QString &name, const QIcon &fallback)

This is an overloaded function.

Returns the QIcon corresponding to name in the current icon theme.

If the current theme does not provide an icon for name, the fallback icon theme is consulted, before falling back to looking up standalone icon files in the fallback icon search path.

If no icon is found fallback is returned.

This is useful to provide a guaranteed fallback, regardless of whether the current set of icon themes and fallbacks paths support the requested icon.

For example:

     QIcon undoicon = QIcon::fromTheme("edit-undo", QIcon(":/undo.png"));

See also fallbackIconTheme() and fallbackSearchPaths().

### `[static]` bool QIcon::hasThemeIcon(const QString &name)

Returns `true` if there is an icon available for name in the current icon theme or any of the fallbacks, as described by fromTheme(), otherwise returns `false`.

See also themeSearchPaths(), fromTheme(), and setThemeName().

### bool QIcon::isMask() const

Returns `true` if this icon has been marked as a mask image. Certain platforms render mask icons differently (for example, menu icons on macOS).

See also setIsMask().

### bool QIcon::isNull() const

Returns `true` if the icon is empty; otherwise returns `false`.

An icon is empty if it has neither a pixmap nor a filename.

Note: Even a non-null icon might not be able to create valid pixmaps, eg. if the file does not exist or cannot be read.

### QString QIcon::name() const

Returns the name used to create the icon, if available.

Depending on the way the icon was created, it may have an associated name. This is the case for icons created with fromTheme().

See also fromTheme() and QIconEngine::iconName().

### void QIcon::paint(QPainter *painter, const QRect &rect, Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const

Uses the painter to paint the icon with specified alignment, required mode, and state into the rectangle rect.

See also actualSize() and pixmap().

### void QIcon::paint(QPainter *painter, int x, int y, int w, int h, Qt::Alignment alignment = Qt::AlignCenter, QIcon::Mode mode = Normal, QIcon::State state = Off) const

This is an overloaded function.

Paints the icon into the rectangle QRect(x, y, w, h).

### QPixmap QIcon::pixmap(const QSize &size, QIcon::Mode mode = Normal, QIcon::State state = Off) const

Returns a pixmap with the requested size, mode, and state, generating one if necessary. The pixmap might be smaller than requested, but never larger, unless the device-pixel ratio of the returned pixmap is larger than 1.

See also actualSize() and paint().

### QPixmap QIcon::pixmap(int w, int h, QIcon::Mode mode = Normal, QIcon::State state = Off) const

This is an overloaded function.

Returns a pixmap of size QSize(w, h). The pixmap might be smaller than requested, but never larger, unless the device-pixel ratio of the returned pixmap is larger than 1.

### QPixmap QIcon::pixmap(int extent, QIcon::Mode mode = Normal, QIcon::State state = Off) const

This is an overloaded function.

Returns a pixmap of size QSize(extent, extent). The pixmap might be smaller than requested, but never larger, unless the device-pixel ratio of the returned pixmap is larger than 1.

### `[since 6.0]` QPixmap QIcon::pixmap(const QSize &size, qreal devicePixelRatio, QIcon::Mode mode = Normal, QIcon::State state = Off) const

This is an overloaded function.

Returns a pixmap with the requested size, devicePixelRatio, mode, and state, generating one if necessary.

This function was introduced in Qt 6.0.

See also actualSize() and paint().

### `[static]` void QIcon::setFallbackSearchPaths(const QStringList &paths)

Sets the fallback search paths for icons to paths.

The fallback search paths are consulted for standalone icon files if the current icon theme or fallback icon theme do not provide results for an icon lookup.

For example:

     QIcon::setFallbackSearchPaths(QIcon::fallbackSearchPaths() << "my/search/path");

See also fallbackSearchPaths() and setThemeSearchPaths().

### `[static]` void QIcon::setFallbackThemeName(const QString &name)

Sets the fallback icon theme to name.

The fallback icon theme is consulted for icons not provided by the current icon theme, or if the current icon theme does not exist.

The name should correspond to theme in the same format as documented by setThemeName(), and will be looked up in themeSearchPaths().

Note: Fallback icon themes should be set before creating QGuiApplication, to ensure correct initialization.

See also fallbackThemeName(), themeSearchPaths(), and themeName().

### void QIcon::setIsMask(bool isMask)

Indicate that this icon is a mask image(boolean isMask), and hence can potentially be modified based on where it's displayed.

See also isMask().

### `[static]` void QIcon::setThemeSearchPaths(const QStringList &paths)

Sets the search paths for icon themes to paths.

The content of paths should follow the theme format documented by setThemeName().

See also themeSearchPaths(), fromTheme(), and setThemeName().

### `[noexcept]` void QIcon::swap(QIcon &other)

Swaps icon other with this icon. This operation is very fast and never fails.

### `[static]` QStringList QIcon::themeSearchPaths()

Returns the search paths for icon themes.

The default search paths will be defined by the platform. All platforms will also have the resource directory `:\icons` as a fallback.

See also setThemeSearchPaths(), fromTheme(), and setThemeName().

### QVariant QIcon::operator QVariant() const

Returns the icon as a QVariant.

### QIcon &QIcon::operator=(const QIcon &other)

Assigns the other icon to this icon and returns a reference to this icon.

### `[noexcept]` QIcon &QIcon::operator=(QIcon &&other)

Move-assigns other to this QIcon instance.

## Related Non-Members

### QDataStream &operator<<(QDataStream &stream, const QIcon &icon)

Writes the given icon to the given stream as a PNG image. If the icon contains more than one image, all images will be written to the stream. Note that writing the stream to a file will not produce a valid image file.

### QDataStream &operator>>(QDataStream &stream, QIcon &icon)

Reads an image, or a set of images, from the given stream into the given icon.