Detailed Description
The QPointArray class provides an array of points.
A QPointArray is an array of QPoint objects. In addition to the
functions provided by QMemArray, QPointArray provides some
point-specific functions.
For convenient reading and writing of the point data use
setPoints(), putPoints(), point(), and setPoint().
For geometry operations use boundingRect() and translate(). There
is also the QWMatrix::map() function for more general
transformations of QPointArrays. You can also create arcs and
ellipses with makeArc() and makeEllipse().
Among others, QPointArray is used by QPainter::drawLineSegments(),
QPainter::drawPolyline(), QPainter::drawPolygon() and
QPainter::drawCubicBezier().
Note that because this class is a QMemArray, copying an array and
modifying the copy modifies the original as well, i.e. a shallow copy. If you need a deep copy use copy() or detach(), for example:
void drawGiraffe( const QPointArray & r, QPainter * p )
{
QPointArray tmp = r;
tmp.detach();
// some code that modifies tmp
p->drawPoints( tmp );
}
If you forget the tmp.detach(), the const array will be modified.
See also QPainter, QWMatrix, QMemArray, Graphics Classes, Image Processing Classes, and Implicitly and Explicitly Shared Classes.
Member Function Documentation
QPointArray::QPointArray ()
Constructs a null point array.
See also isNull().
QPointArray::QPointArray ( int size )
Constructs a point array with room for size points. Makes a
null array if size == 0.
See also resize() and isNull().
QPointArray::QPointArray ( const QPointArray & a )
Constructs a shallow copy of the point array a.
See also copy() and detach().
QPointArray::QPointArray ( const QRect & r, bool closed = FALSE )
Constructs a point array from the rectangle r.
If closed is FALSE, then the point array just contains the
following four points in the listed order: r.topLeft(),
r.topRight(), r.bottomRight() and r.bottomLeft().
If closed is TRUE, then a fifth point is set to r.topLeft().
QPointArray::~QPointArray ()
Destroys the point array.
QRect QPointArray::boundingRect () const
Returns the bounding rectangle of the points in the array, or
QRect(0,0,0,0) if the array is empty.
QPointArray QPointArray::copy () const
Creates a deep copy of the array.
See also detach().
QPointArray QPointArray::cubicBezier () const
Returns the Bezier points for the four control points in this
array.
void QPointArray::makeArc ( int x, int y, int w, int h, int a1, int a2 )
Sets the points of the array to those describing an arc of an
ellipse with size, width w by height h, and position (x,
y), starting from angle a1 and spanning by angle a2. The
resulting array has sufficient resolution for pixel accuracy (see
the overloaded function which takes an additional QWMatrix
parameter).
Angles are specified in 16ths of a degree, i.e. a full circle
equals 5760 (16*360). Positive values mean counter-clockwise,
whereas negative values mean the clockwise direction. Zero degrees
is at the 3 o'clock position.
See the angle diagram.
void QPointArray::makeArc ( int x, int y, int w, int h, int a1, int a2, const QWMatrix & xf )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Sets the points of the array to those describing an arc of an
ellipse with width w and height h and position (x, y),
starting from angle a1, and spanning angle by a2, and
transformed by the matrix xf. The resulting array has
sufficient resolution for pixel accuracy.
Angles are specified in 16ths of a degree, i.e. a full circle
equals 5760 (16*360). Positive values mean counter-clockwise,
whereas negative values mean the clockwise direction. Zero degrees
is at the 3 o'clock position.
See the angle diagram.
void QPointArray::makeEllipse ( int x, int y, int w, int h )
Sets the points of the array to those describing an ellipse with
size, width w by height h, and position (x, y).
The returned array has sufficient resolution for use as pixels.
Assigns a shallow copy of a to this point array and returns a
reference to this point array.
Equivalent to assign(a).
See also copy() and detach().
void QPointArray::point ( uint index, int * x, int * y ) const
Reads the coordinates of the point at position index within the
array and writes them into *x and *y.
QPoint QPointArray::point ( uint index ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the point at position index within the array.
bool QPointArray::putPoints ( int index, int nPoints, int firstx, int firsty, ... )
Copies nPoints points from the variable argument list into this
point array from position index, and resizes the point array if
index+nPoints exceeds the size of the array.
Returns TRUE if successful, or FALSE if the array could not be
resized (typically due to lack of memory).
The example code creates an array with three points (4,5), (6,7)
and (8,9), by expanding the array from 1 to 3 points:
QPointArray a( 1 );
a[0] = QPoint( 4, 5 );
a.putPoints( 1, 2, 6,7, 8,9 ); // index == 1, points == 2
This has the same result, but here putPoints overwrites rather
than extends:
QPointArray a( 3 );
a.putPoints( 0, 3, 4,5, 0,0, 8,9 );
a.putPoints( 1, 1, 6,7 );
The points are given as a sequence of integers, starting with firstx then firsty, and so on.
See also resize().
bool QPointArray::putPoints ( int index, int nPoints, const QPointArray & from, int fromIndex = 0 )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
This version of the function copies nPoints from from into
this array, starting at index in this array and fromIndex in
from. fromIndex is 0 by default.
QPointArray a;
a.putPoints( 0, 3, 1,2, 0,0, 5,6 );
// a is now the three-point array ( 1,2, 0,0, 5,6 );
QPointArray b;
b.putPoints( 0, 3, 4,4, 5,5, 6,6 );
// b is now ( 4,4, 5,5, 6,6 );
a.putPoints( 2, 3, b );
// a is now ( 1,2, 0,0, 4,4, 5,5, 6,6 );
void QPointArray::setPoint ( uint index, int x, int y )
Sets the point at position index in the array to (x, y).
Example: themes/wood.cpp.
void QPointArray::setPoint ( uint i, const QPoint & p )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Sets the point at array index i to p.
void QPointArray::translate ( int dx, int dy )
Translates all points in the array by (dx, dy).
Related Functions
Writes the point array, a to the stream s and returns a
reference to the stream.
See also Format of the QDataStream operators.
Reads a point array, a from the stream s and returns a
reference to the stream.
See also Format of the QDataStream operators.
This file is part of the Qt toolkit.
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