qpaintdevice.3qt

Linux下的基于X11的图形开发环境。

'\" t
.TH QPaintDevice 3qt "9 December 2002" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2001 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QPaintDevice \- The base class of objects that can be painted
.SH SYNOPSIS
\fC#include <qpaintdevice.h>\fR
.PP
Inherited by QPixmap, QWidget, QPicture, and QPrinter.
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "virtual \fB~QPaintDevice\fR ()"
.br
.ti -1c
.BI "bool \fBisExtDev\fR () const"
.br
.ti -1c
.BI "bool \fBpaintingActive\fR () const"
.br
.ti -1c
.BI "virtual HDC \fBhandle\fR () const"
.br
.ti -1c
.BI "virtual Qt::HANDLE \fBhandle\fR () const"
.br
.ti -1c
.BI "Display * \fBx11Display\fR () const"
.br
.ti -1c
.BI "int \fBx11Screen\fR () const"
.br
.ti -1c
.BI "int \fBx11Depth\fR () const"
.br
.ti -1c
.BI "int \fBx11Cells\fR () const"
.br
.ti -1c
.BI "Qt::HANDLE \fBx11Colormap\fR () const"
.br
.ti -1c
.BI "bool \fBx11DefaultColormap\fR () const"
.br
.ti -1c
.BI "void * \fBx11Visual\fR () const"
.br
.ti -1c
.BI "bool \fBx11DefaultVisual\fR () const"
.br
.in -1c
.SS "Static Public Members"
.in +1c
.ti -1c
.BI "Display * \fBx11AppDisplay\fR ()"
.br
.ti -1c
.BI "int \fBx11AppScreen\fR ()"
.br
.ti -1c
.BI "int \fBx11AppDpiX\fR ()"
.br
.ti -1c
.BI "int \fBx11AppDpiY\fR ()"
.br
.ti -1c
.BI "void \fBx11SetAppDpiX\fR ( int dpi )"
.br
.ti -1c
.BI "void \fBx11SetAppDpiY\fR ( int dpi )"
.br
.ti -1c
.BI "int \fBx11AppDepth\fR ()"
.br
.ti -1c
.BI "int \fBx11AppCells\fR ()"
.br
.ti -1c
.BI "Qt::HANDLE \fBx11AppRootWindow\fR ()"
.br
.ti -1c
.BI "Qt::HANDLE \fBx11AppColormap\fR ()"
.br
.ti -1c
.BI "bool \fBx11AppDefaultColormap\fR ()"
.br
.ti -1c
.BI "void * \fBx11AppVisual\fR ()"
.br
.ti -1c
.BI "bool \fBx11AppDefaultVisual\fR ()"
.br
.ti -1c
.BI "int \fBx11AppDepth\fR ( int screen )"
.br
.ti -1c
.BI "int \fBx11AppCells\fR ( int screen )"
.br
.ti -1c
.BI "Qt::HANDLE \fBx11AppRootWindow\fR ( int screen )"
.br
.ti -1c
.BI "Qt::HANDLE \fBx11AppColormap\fR ( int screen )"
.br
.ti -1c
.BI "void * \fBx11AppVisual\fR ( int screen )"
.br
.ti -1c
.BI "bool \fBx11AppDefaultColormap\fR ( int screen )"
.br
.ti -1c
.BI "bool \fBx11AppDefaultVisual\fR ( int screen )"
.br
.ti -1c
.BI "int \fBx11AppDpiX\fR ( int screen )"
.br
.ti -1c
.BI "int \fBx11AppDpiY\fR ( int screen )"
.br
.ti -1c
.BI "void \fBx11SetAppDpiX\fR ( int dpi, int screen )"
.br
.ti -1c
.BI "void \fBx11SetAppDpiY\fR ( int dpi, int screen )"
.br
.in -1c
.SS "Protected Members"
.in +1c
.ti -1c
.BI "\fBQPaintDevice\fR ( uint devflags )"
.br
.ti -1c
.BI "virtual bool \fBcmd\fR ( int, QPainter *, QPDevCmdParam * )"
.br
.in -1c
.SH RELATED FUNCTION DOCUMENTATION
.in +1c
.ti -1c
.BI "void \fBbitBlt\fR ( QPaintDevice * dst, int dx, int dy, const QPaintDevice * src, int sx, int sy, int sw, int sh, Qt::RasterOp rop, bool ignoreMask )"
.br
.ti -1c
.BI "void \fBbitBlt\fR ( QPaintDevice * dst, const QPoint & dp, const QPaintDevice * src, const QRect & sr, RasterOp rop )"
.br
.in -1c
.SH DESCRIPTION
The QPaintDevice class is the base class of objects that can be painted.
.PP
A paint device is an abstraction of a two-dimensional space that can be drawn using a QPainter. The drawing capabilities are implemented by the subclasses QWidget, QPixmap, QPicture and QPrinter.
.PP
The default coordinate system of a paint device has its origin located at the top-left position. X increases to the right and Y increases downward. The unit is one pixel. There are several ways to set up a user-defined coordinate system using the painter, for example, using QPainter::setWorldMatrix().
.PP
Example (draw on a paint device):
.PP
.nf
.br
    void MyWidget::paintEvent( QPaintEvent * )
.br
    {
.br
        QPainter p;                       // our painter
.br
        p.begin( this );                  // start painting the widget
.br
        p.setPen( red );                  // red outline
.br
        p.setBrush( yellow );             // yellow fill
.br
        p.drawEllipse( 10, 20, 100,100 ); // 100x100 ellipse at position (10, 20)
.br
        p.end();                          // painting done
.br
    }
.br
.fi
.PP
The bit block transfer is an extremely useful operation for copying pixels from one paint device to another (or to itself). It is implemented as the global function bitBlt().
.PP
Example (scroll widget contents 10 pixels to the right):
.PP
.nf
.br
    bitBlt( myWidget, 10, 0, myWidget );
.br
.fi
.PP
\fBWarning:\fR Qt requires that a QApplication object exists before any paint devices can be created. Paint devices access window system resources, and these resources are not initialized before an application object is created.
.PP