Qt Reference Documentation

- Qt 4.8
- ALL VERSIONS

- A
- A
- A
- Print

# Q3Painter Class Reference

The Q3Painter class is a Qt 3 compatibility wrapper for QPainter. More...

     #include <Q3Painter>

This class is part of the Qt 3 support library. It is provided to keep old source code working. We strongly advise against using it in new code. See Porting to Qt 4 for more information.

Inherits: QPainter.

- List of all members, including inherited members

## Public Functions

| Q3Painter ()
| Q3Painter ( QPaintDevice * pdev )
void | drawArc ( const QRect & r, int a, int alen )
void | drawArc ( int x, int y, int w, int h, int startAngle, int spanAngle )
void | drawChord ( const QRect & r, int a, int alen )
void | drawChord ( int x, int y, int w, int h, int startAngle, int spanAngle )
void | drawEllipse ( const QRect & r )
void | drawEllipse ( int x, int y, int width, int height )
void | drawPie ( const QRect & r, int a, int alen )
void | drawPie ( int x, int y, int w, int h, int startAngle, int spanAngle )
void | drawRect ( const QRect & r )
void | drawRect ( int x, int y, int w, int h )
void | drawRoundRect ( const QRect & r, int xrnd = 25, int yrnd = 25 )
void | drawRoundRect ( int x, int y, int w, int h, int xrnd = 25, int yrnd = 25 )

- 189 public functions inherited from QPainter

## Detailed Description

The Q3Painter class is a Qt 3 compatibility wrapper for QPainter.

Prior to Qt 4, QPainter specialized the pen drawing for rectangle based functions (in particular: drawRect, drawEllipse, drawRoundRect, drawArc, drawChord and drawPie). When stroking a rectangle of width 10, the pen would draw a rectangle of width 10. Drawing a polygon defined by the corner points of the same rectangle the stroke would have a width of 11.

The reason for this is best explained using the picture below:

As we can see, stroking the rectangle so it gets a width of 10, means the pen is drawn on a rectangle on width 9. The polygon, however follows a consistent model.

In Qt 4, all rectangle based functions have changed to follow the polygon approach, which means that the rectangle defines the size of the fill, and the pen follows the edges of the shape. For pen widths of 0 and 1 this means that the stroke will be inside the shape on the left and the top and outside on the bottom and right.

The reason for the change in Qt 4 is so that we provide consistency for all drawing functions even with complex transformations.

## Member Function Documentation

### Q3Painter::Q3Painter ()

Constructs a Q3Painter.

### Q3Painter::Q3Painter ( QPaintDevice * pdev )

Constructs a Q3Painter that operates on device pdev.

### void Q3Painter::drawArc ( const QRect & r, int a, int alen )

Draws an arc defined by the rectangle r, the start angle a and the arc length alen.

The angles a and alen are 1/16th of a degree, i.e. a full circle equals 5760 (16*360). Positive values of a and alen mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

Example:

     QPainter p(myWidget);
     p.drawArc(QRect(10,10, 70,100), 100*16, 160*16); // draws a "(" arc

See also drawPie() and drawChord().

### void Q3Painter::drawArc ( int x, int y, int w, int h, int startAngle, int spanAngle )

This is an overloaded function.

Draws the arc that fits inside the rectangle (x, y, w, h), with the given startAngle and spanAngle.

### void Q3Painter::drawChord ( const QRect & r, int a, int alen )

Draws a chord defined by the rectangle r, the start angle a and the arc length alen.

The chord is filled with the current brush().

The angles a and alen are 1/16th of a degree, i.e. a full circle equals 5760 (16*360). Positive values of a and alen mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

See also drawArc() and drawPie().

### void Q3Painter::drawChord ( int x, int y, int w, int h, int startAngle, int spanAngle )

This is an overloaded function.

Draws a chord that fits inside the rectangle (x, y, w, h) with the given startAngle and spanAngle.

### void Q3Painter::drawEllipse ( const QRect & r )

Draws the ellipse that fits inside the bounds r using the current pen and brush.

### void Q3Painter::drawEllipse ( int x, int y, int width, int height )

This is an overloaded function.

Draws an ellipse that fits inside the bounds specified by x, y, width and height using the current pen and brush.

### void Q3Painter::drawPie ( const QRect & r, int a, int alen )

Draws a pie defined by the rectangle r, the start angle a and the arc length alen.

The pie is filled with the current brush().

The angles a and alen are 1/16th of a degree, i.e. a full circle equals 5760 (16*360). Positive values of a and alen mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

See also drawArc() and drawChord().

### void Q3Painter::drawPie ( int x, int y, int w, int h, int startAngle, int spanAngle )

This is an overloaded function.

Draws a pie segment that fits inside the bounds (x, y, w, h) with the given startAngle and spanAngle.

### void Q3Painter::drawRect ( const QRect & r )

Draws a rectangle that fits inside the rectangle r using the current pen and brush.

### void Q3Painter::drawRect ( int x, int y, int w, int h )

This is an overloaded function.

Draws the rectangle that fits inside the bounds specified by x, y, w and h using the current pen and brush.

### void Q3Painter::drawRoundRect ( const QRect & r, int xrnd = 25, int yrnd = 25 )

Draws a rounded rect that fits into the bounds r using the current pen and brush. The parameters xrnd and yrnd specifies the roundness in x and y direction.

### void Q3Painter::drawRoundRect ( int x, int y, int w, int h, int xrnd = 25, int yrnd = 25 )

This is an overloaded function.

Draws a rounded rect that fits into the bounds x, y, w and h using the current pen and brush. The parameters xrnd and yrnd specifies the roundness in x and y direction.