---
name: "QwtPaintBuffer"
section: "3"
platform: "linux"
package: "libqwt-doc"
version: "4.2.0-6"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/QwtPaintBuffer"
---

# QwtPaintBuffer(3)

## NAME

QwtPaintBuffer -

## SYNOPSIS

## Detailed Description

Paint buffer for Qwt widgets.

QwtPaintBuffer offers a simple way to en/disable double buffering. Double buffering is enabled as default and in general there will be no reason to change this.

Definition at line 26 of file qwt\_paint\_buffer.h.

### Public Member Functions

**QwtPaintBuffer** ()\
 **QwtPaintBuffer** (QPaintDevice \*, const QRect &, QPainter \*p=NULL)\
 virtual **~QwtPaintBuffer** ()\
 void **open** (QPaintDevice \*, const QRect &, QPainter \*p=NULL)\
 void **close** ()\
 QPainter \* **painter** ()\
 const QPaintDevice \* **device** ()\
 const QPixmap & **buffer** () const\

### Static Public Member Functions

void **setEnabled** (bool enable)\
 bool **isEnabled** ()\

### Protected Member Functions

void **flush** ()\

## Constructor & Destructor Documentation

### QwtPaintBuffer::QwtPaintBuffer ()

Default constructor.

Definition at line 17 of file qwt\_paint\_buffer.cpp.

### QwtPaintBuffer::QwtPaintBuffer (QPaintDevice \* device, const QRect & rect, QPainter \* painter = `NULL`)

Create an open paint buffer

**Parameters:**

*device* Device to paint on \
 *rect* Rect to paint on \
 *painter* Painter to paint on device. In case of 0 QwtPaintBuffer uses an internal painter

**See also:**

**QwtPaintBuffer::open()**

Definition at line 34 of file qwt\_paint\_buffer.cpp.

References open().

### QwtPaintBuffer::~QwtPaintBuffer ()` [virtual]`

Closes the buffer

**See also:**

**QwtPaintBuffer::close()**

Definition at line 47 of file qwt\_paint\_buffer.cpp.

References close().

## Member Function Documentation

### const QPixmap& QwtPaintBuffer::buffer () const

Return Buffer used for double buffering.

Definition at line 44 of file qwt\_paint\_buffer.h.

Referenced by QwtPlotCanvas::drawCanvas().

### void QwtPaintBuffer::close ()

Flush the internal pixmap buffer to the device and close the buffer. Definition at line 178 of file qwt\_paint\_buffer.cpp.

References flush().

Referenced by open(), and ~QwtPaintBuffer().

### const QPaintDevice \* QwtPaintBuffer::device ()

**Returns:**

Device to paint on

Definition at line 66 of file qwt\_paint\_buffer.cpp.

Referenced by flush().

### void QwtPaintBuffer::flush ()` [protected]`

Flush the internal pixmap buffer to the device. Definition at line 151 of file qwt\_paint\_buffer.cpp.

References device().

Referenced by close().

### bool QwtPaintBuffer::isEnabled ()` [static]`

**Returns:**

TRUE if double buffering is enabled, FALSE otherwise.

Definition at line 84 of file qwt\_paint\_buffer.cpp.

Referenced by QwtPlotCanvas::drawCanvas(), and open().

### void QwtPaintBuffer::open (QPaintDevice \* device, const QRect & rect, QPainter \* painter = `NULL`)

Open the buffer

**Parameters:**

*device* Device to paint on \
 *rect* Rect to paint on \
 *painter* Painter to paint on device. In case of 0 QwtPaintBuffer uses an internal painter

Definition at line 97 of file qwt\_paint\_buffer.cpp.

References close(), and isEnabled().

Referenced by QwtPaintBuffer().

### QPainter \* QwtPaintBuffer::painter ()

**Returns:**

Depending on **isEnabled()** the painter connected to an internal pixmap buffer otherwise the painter connected to the device.

Definition at line 58 of file qwt\_paint\_buffer.cpp.

Referenced by QwtPlotCanvas::drawCanvas(), QwtWheel::paintEvent(), QwtThermo::paintEvent(), QwtSlider::paintEvent(), QwtScale::paintEvent(), QwtKnob::paintEvent(), and QwtDial::paintEvent().

### void QwtPaintBuffer::setEnabled (bool enable)` [static]`

Enable/Disable double buffering. Please note that this is a global switch for all QwtPaintBuffers, but won't change opened buffers. Definition at line 76 of file qwt\_paint\_buffer.cpp.

## Author

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