QIcon Class

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.

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

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

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

Constructs a null icon.

Constructs an icon from a pixmap.

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.

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

Constructs a copy of other. This is very fast.

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

Destroys the icon.

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▲

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