QRegion(3qt)

📦 version 3.3.8b, in fedora 43, fedora 44

🌸 QRegion 💖 — the QRegion(3qt) manual, bestie edition ✨

okay so sit down, grab a strawberry 🍓, because we're about to talk about QRegion and honestly? it's giving clip region for a painter energy and it ATE. 👑

✨ NAME ✨

QRegion — clip region for a painter 🎨

🦋 SYNOPSIS 🦋

#include <qregion.h>

💅 Public Members

enum RegionType { Rectangle, Ellipse }
QRegion ()
QRegion ( int x, int y, int w, int h, RegionType t = Rectangle )
QRegion ( const QRect & r, RegionType t = Rectangle )
QRegion ( const QPointArray & a, bool winding = FALSE )
QRegion ( const QRegion & r )
QRegion ( const QBitmap & bm )
~QRegion ()
QRegion & operator= ( const QRegion & r )
bool isNull () const
bool isEmpty () const
bool contains ( const QPoint & p ) const
bool contains ( const QRect & r ) const
void translate ( int dx, int dy )
QRegion unite ( const QRegion & r ) const
QRegion intersect ( const QRegion & r ) const
QRegion subtract ( const QRegion & r ) const
QRegion eor ( const QRegion & r ) const
QRect boundingRect () const
QMemArray<QRect> rects () const
const QRegion operator| ( const QRegion & r ) const
const QRegion operator+ ( const QRegion & r ) const
const QRegion operator& ( const QRegion & r ) const
const QRegion operator- ( const QRegion & r ) const
const QRegion operator^ ( const QRegion & r ) const
QRegion & operator|= ( const QRegion & r )
QRegion & operator+= ( const QRegion & r )
QRegion & operator&= ( const QRegion & r )
QRegion & operator-= ( const QRegion & r )
QRegion & operator^= ( const QRegion & r )
bool operator== ( const QRegion & r ) const
bool operator!= ( const QRegion & r ) const
HRGN handle () const
QDataStream & operator<< ( QDataStream & s, const QRegion & r )
QDataStream & operator>> ( QDataStream & s, QRegion & r )

💖 DESCRIPTION 💖

The QRegion class specifies a clip region for a painter. periodt. ✨

QRegion is used with QPainter::setClipRegion() to limit the paint area to what needs to be painted. There's also a QWidget::repaint() that takes a QRegion parameter. QRegion is the best tool for reducing flicker. 🔥 no cap, that's literally the whole point and she delivers.

A region can be created from a rectangle, an ellipse, a polygon or a bitmap. 🦋 Complex regions may be created by combining simple regions using unite(), intersect(), subtract() or eor() (exclusive or). You can move a region using translate().

You can test whether a region isNull(), isEmpty() or if it contains() a QPoint or QRect. The bounding rectangle is given by boundingRect(). 👑

The function rects() gives a decomposition of the region into rectangles.

Example of using complex regions — look at her, she's serving:

void MyWidget::paintEvent( QPaintEvent * )
{
    QPainter p;                         // our painter
    QRegion r1( QRect(100,100,200,80),  // r1 = elliptic region
                QRegion::Ellipse );
    QRegion r2( QRect(100,120,90,30) ); // r2 = rectangular region
    QRegion r3 = r1.intersect( r2 );    // r3 = intersection
    p.begin( this );                    // start painting widget
    p.setClipRegion( r3 );              // set clip region
    ...                                 // paint clipped graphics
    p.end();                            // painting done
}

QRegion is an implicitly shared class. 💜 shared but make it lowkey efficient.

⚠️ Warning: Due to window system limitations, the whole coordinate space for a region is limited to the points between -32767 and 32767 on Mac OS X and Windows 95/98/ME. 😭 bestie do NOT go past those numbers, she will simply not vibe with it.

See also QPainter::setClipRegion(), QPainter::setClipRect(), Graphics Classes, and Image Processing Classes. 🫶

🎀 Member Type Documentation 🎀

QRegion::RegionType

Specifies the shape of the region to be created. ✨

  • QRegion::Rectangle — the region covers the entire rectangle.
  • QRegion::Ellipse — the region is an ellipse inside the rectangle.

👑 MEMBER FUNCTION DOCUMENTATION 👑

QRegion::QRegion ()

Constructs a null region.

See also isNull().

QRegion::QRegion ( int x, int y, int w, int h, RegionType t = Rectangle )

Constructs a rectangular or elliptic region. 🌸

If t is Rectangle, the region is the filled rectangle (x, y, w, h). If t is Ellipse, the region is the filled ellipse with center at (x + w / 2, y + h / 2) and size (w ,h ).

QRegion::QRegion ( const QRect & r, RegionType t = Rectangle )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function. 💅

Create a region based on the rectange r with region type t.

If the rectangle is invalid a null region will be created. 😭

See also QRegion::RegionType.

QRegion::QRegion ( const QPointArray & a, bool winding = FALSE )

Constructs a polygon region from the point array a. 🦋

If winding is TRUE, the polygon region is filled using the winding algorithm, otherwise the default even-odd fill algorithm is used.

⚠️ This constructor may create complex regions that will slow down painting when used. 🔥 beautiful but expensive, iykyk.

QRegion::QRegion ( const QRegion & r )

Constructs a new region which is equal to region r. ✨

QRegion::QRegion ( const QBitmap & bm )

Constructs a region from the bitmap bm.

The resulting region consists of the pixels in bitmap bm that are color1, as if each pixel was a 1 by 1 rectangle. 🎀

⚠️ This constructor may create complex regions that will slow down painting when used. Note that drawing masked pixmaps can be done much faster using QPixmap::setMask(). 👀 so maybe use that instead bestie.

QRegion::~QRegion ()

Destroys the region. 💀 she's gone, she's resting.

QRect QRegion::boundingRect () const

Returns the bounding rectangle of this region. An empty region gives a rectangle that is QRect::isNull(). 🌸

bool QRegion::contains ( const QPoint & p ) const

Returns TRUE if the region contains the point p; otherwise returns FALSE. 💅

bool QRegion::contains ( const QRect & r ) const

This is an overloaded member function, provided for convenience. It behaves essentially like the above function. ✨

Returns TRUE if the region overlaps the rectangle r; otherwise returns FALSE.

QRegion QRegion::eor ( const QRegion & r ) const

Returns a region which is the exclusive or (XOR) of this region and r. 🔥

🖼️ [Image Omitted]

The figure shows the exclusive or of two elliptical regions. 🌈

HRGN QRegion::handle () const

Returns the region's handle. 👑

QRegion QRegion::intersect ( const QRegion & r ) const

Returns a region which is the intersection of this region and r. 💖

🖼️ [Image Omitted]

The figure shows the intersection of two elliptical regions. ✨

bool QRegion::isEmpty () const

Returns TRUE if the region is empty; otherwise returns FALSE. An empty region is a region that contains no points. 🫶

Example — literally the vibe check, watch:

QRegion r1( 10, 10, 20, 20 );
QRegion r2( 40, 40, 20, 20 );
QRegion r3;
r1.isNull();             // FALSE
r1.isEmpty();            // FALSE
r3.isNull();             // TRUE
r3.isEmpty();            // TRUE
r3 = r1.intersect( r2 ); // r3 = intersection of r1 and r2
r3.isNull();             // FALSE
r3.isEmpty();            // TRUE
r3 = r1.unite( r2 );     // r3 = union of r1 and r2
r3.isNull();             // FALSE
r3.isEmpty();            // FALSE

See also isNull().

bool QRegion::isNull () const

Returns TRUE if the region is a null region; otherwise returns FALSE.

A null region is a region that has not been initialized. A null region is always empty. 💜

See also isEmpty().

bool QRegion::operator!= ( const QRegion & r ) const

Returns TRUE if the region is different from r; otherwise returns FALSE. 💅 not the same, not the vibe.

const QRegion QRegion::operator& ( const QRegion & r ) const

Applies the intersect() function to this region and r. r1&r2 is equivalent to r1.intersect(r2) ✨

See also intersect().

QRegion & QRegion::operator&= ( const QRegion & r )

Applies the intersect() function to this region and r and assigns the result to this region. r1&=r2 is equivalent to r1=r1.intersect(r2) 💖

See also intersect().

const QRegion QRegion::operator+ ( const QRegion & r ) const

Applies the unite() function to this region and r. r1+r2 is equivalent to r1.unite(r2) 🔥

See also unite() and operator|().

QRegion & QRegion::operator+= ( const QRegion & r )

Applies the unite() function to this region and r and assigns the result to this region. r1+=r2 is equivalent to r1=r1.unite(r2) 🌸

See also intersect().

const QRegion QRegion::operator- ( const QRegion & r ) const

Applies the subtract() function to this region and r. r1-r2 is equivalent to r1.subtract(r2) 💅

See also subtract().

QRegion & QRegion::operator-= ( const QRegion & r )

Applies the subtract() function to this region and r and assigns the result to this region. r1-=r2 is equivalent to r1=r1.subtract(r2) ✨

See also subtract().

QRegion & QRegion::operator= ( const QRegion & r )

Assigns r to this region and returns a reference to the region. 🎀 she's copying her whole look, respectfully.

bool QRegion::operator== ( const QRegion & r ) const

Returns TRUE if the region is equal to r; otherwise returns FALSE. 👑

const QRegion QRegion::operator^ ( const QRegion & r ) const

Applies the eor() function to this region and r. r1^r2 is equivalent to r1.eor(r2) 🔥

See also eor().

QRegion & QRegion::operator^= ( const QRegion & r )

Applies the eor() function to this region and r and assigns the result to this region. r1^=r2 is equivalent to r1=r1.eor(r2) 💜

See also eor().

const QRegion QRegion::operator| ( const QRegion & r ) const

Applies the unite() function to this region and r. r1|r2 is equivalent to r1.unite(r2) 🌈

See also unite() and operator+().

QRegion & QRegion::operator|= ( const QRegion & r )

Applies the unite() function to this region and r and assigns the result to this region. r1|=r2 is equivalent to r1=r1.unite(r2) 💖

See also unite().

QMemArray<QRect> QRegion::rects () const

Returns an array of non-overlapping rectangles that make up the region. ✨

The union of all the rectangles is equal to the original region. 🫶 put them all together and you get her back, no notes.

QRegion QRegion::subtract ( const QRegion & r ) const

Returns a region which is r subtracted from this region. 💅

🖼️ [Image Omitted]

The figure shows the result when the ellipse on the right is subtracted from the ellipse on the left. (left-right )

void QRegion::translate ( int dx, int dy )

Translates (moves) the region dx along the X axis and dy along the Y axis. 🦋 she's moving, she's going places.

QRegion QRegion::unite ( const QRegion & r ) const

Returns a region which is the union of this region and r. 🌸

🖼️ [Image Omitted]

The figure shows the union of two elliptical regions. ✨

QDataStream & operator<< ( QDataStream & s, const QRegion & r )

Writes the region r to the stream s and returns a reference to the stream. 💜

See also Format of the QDataStream operators.

QDataStream & operator>> ( QDataStream & s, QRegion & r )

Okay so this one is the read-in bestie of the stream operators 💖 It takes the stream s, reads a region out of it, drops that region into r, and then returns a reference to the stream. That's it, that's the whole vibe. ✨

See also Format of the QDataStream operators. iykyk 🫶

✨ SEE ALSO ✨

Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the license file included in the distribution for a complete license statement. The legal tea is all in there, bestie, no cap. 💅

👑 AUTHOR 👑

Generated automatically from the source code. So yeah, no mysterious human author, just machine magic doing its little thing. 🤖✨

💀 BUGS 💀

If you find a bug in Qt, please report it as described in http://doc.trolltech.com/bughowto.html. Good bug reports help us to help you. Thank you. 🫶

The definitive Qt documentation is provided in HTML format; it is located at $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is provided as a convenience for those users who prefer man pages, although this format is not officially supported by Trolltech. Lowkey a cute lil side quest, but not the main character. 🌸

If you find errors in this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page (qregion.3qt) and the Qt version (3.3.8). That way the fix can actually find you. 💜

And that's the whole page, bestie! Brought to you by Trolltech AS, dated 2 February 2007, and it's QRegion(3qt). Slay, bye 💅✨🎀

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