Qt GUI Overview Paint Devices and Backends

Paint System

Qt's paint system enables painting on screen and print devices using the same API, and is primarily based on the QPainter, QPaintDevice, and QPaintEngine classes.

QPainter is used to perform drawing operations, QPaintDevice is an abstraction of a two-dimensional space that can be painted on using a QPainter, and QPaintEngine provides the interface that the painter uses to draw onto different types of devices. The QPaintEngine class is used internally by QPainter and QPaintDevice, and is hidden from application programmers unless they create their own device type.

The main benefit of this approach is that all painting follows the same painting pipeline making it easy to add support for new features and providing default implementations for unsupported ones.

Topics

Classes for Painting

These classes provide support for painting onto a paint device.

QBitmap	Monochrome (1-bit depth) pixmaps
QBrush	Defines the fill pattern of shapes drawn by QPainter
QColor	Colors based on RGB, HSV or CMYK values
QColorSpace	Color space abstraction
QColorTransform	Transformation between color spaces
QColormap	Maps device independent QColors to device dependent pixel values
QConicalGradient	Used in combination with QBrush to specify a conical gradient brush
QFont	Specifies a query for a font used for drawing text
QFontMetrics	Font metrics information
QFontMetricsF	Font metrics information
QGenericMatrix	Template class that represents a NxM transformation matrix with N columns and M rows
QGradient	Used in combination with QBrush to specify gradient fills
QIcon	Scalable icons in different modes and states
QIconEngine	Abstract base class for QIcon renderers
QImage	Hardware-independent image representation that allows direct access to the pixel data, and can be used as a paint device
QImageReader	Format independent interface for reading images from files or other devices
QImageWriter	Format independent interface for writing images to files or other devices
QLine	Two-dimensional vector using integer precision
QLineF	Two-dimensional vector using floating point precision
QLinearGradient	Used in combination with QBrush to specify a linear gradient brush
QMargins	Defines the four margins of a rectangle
QMarginsF	Defines the four margins of a rectangle
QPageRanges	Represents a collection of page ranges
QPagedPaintDevice	Represents a paint device that supports multiple pages
QPaintDevice	The base class of objects that can be painted on with QPainter
QPaintEngine	Abstract definition of how QPainter draws to a given device on a given platform
QPainter	Performs low-level painting on widgets and other paint devices
QPainterPath	Container for painting operations, enabling graphical shapes to be constructed and reused
QPainterPathStroker	Used to generate fillable outlines for a given painter path
QPdfOutputIntent
QPdfWriter	Class to generate PDFs that can be used as a paint device
QPen	Defines how a QPainter should draw lines and outlines of shapes
QPixmap	Off-screen image representation that can be used as a paint device
QPoint	Defines a point in the plane using integer precision
QPointF	Defines a point in the plane using floating point precision
QPolygon	List of points using integer precision
QPolygonF	List of points using floating point precision
QRadialGradient	Used in combination with QBrush to specify a radial gradient brush
QRect	Defines a rectangle in the plane using integer precision
QRectF	Defines a finite rectangle in the plane using floating point precision
QRegion	Specifies a clip region for a painter
QRgba64	Struct contains a 64-bit RGB color
QRgbaFloat	Struct contains a four part RGBA floating-point color
QSize	Defines the size of a two-dimensional object using integer point precision
QSizeF	Defines the size of a two-dimensional object using floating point precision
QStylePainter	Convenience class for drawing QStyle elements inside a widget
QSupportedWritingSystems	Used when registering fonts with the internal Qt fontdatabase
QSvgGenerator	Paint device that is used to create SVG drawings
QSvgRenderer	Used to draw the contents of SVG files onto paint devices
QSvgWidget	Widget that is used to display the contents of Scalable Vector Graphics (SVG) files
QTransform	Specifies 2D transformations of a coordinate system
QVector2D	Represents a vector or vertex in 2D space

Qt GUI Overview Paint Devices and Backends

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