Viadeo Twitter Google Bookmarks ! Facebook Digg del.icio.us MySpace Yahoo MyWeb Blinklist Netvouz Reddit Simpy StumbleUpon Bookmarks Windows Live Favorites 
Logo Documentation Qt ·  Page d'accueil  ·  Toutes les classes  ·  Classes principales  ·  Annotées  ·  Classes groupées  ·  Fonctions  · 

QCanvasPolygonalItem Class Reference
[canvas module]

The QCanvasPolygonalItem class provides a polygonal canvas item on a QCanvas. More...

#include <qcanvas.h>

Inherits QCanvasItem.

Inherited by QCanvasRectangle, QCanvasPolygon, QCanvasLine, and QCanvasEllipse.

List of all member functions.

Public Members

Protected Members


Detailed Description

The QCanvasPolygonalItem class provides a polygonal canvas item on a QCanvas.

The mostly rectangular classes, such as QCanvasSprite and QCanvasText, use the object's bounding rectangle for movement, repainting and collision calculations. For most other items, the bounding rectangle can be far too large -- a diagonal line being the worst case, and there are many other cases which are also bad. QCanvasPolygonalItem provides polygon-based bounding rectangle handling, etc., which is much faster for non-rectangular items.

Derived classes should try to define as small an area as possible to maximize efficiency, but the polygon must definitely be contained completely within the polygonal area. Calculating the exact requirements is usually difficult, but if you allow a small overestimate it can be easy and quick, while still getting almost all of QCanvasPolygonalItem's speed.

Note that all subclasses must call hide() in their destructor since hide() needs to be able to access areaPoints().

Normally, QCanvasPolygonalItem uses the odd-even algorithm for determining whether an object intersects this object. You can change this to the winding algorithm using setWinding().

The bounding rectangle is available using boundingRect(). The points bounding the polygonal item are retrieved with areaPoints(). Use areaPointsAdvanced() to retrieve the bounding points the polygonal item will have after QCanvasItem::advance(1) has been called.

If the shape of the polygonal item is about to change while the item is visible, call invalidate() before updating with a different result from areaPoints().

By default, QCanvasPolygonalItem objects have a black pen and no brush (the default QPen and QBrush constructors). You can change this with setPen() and setBrush(), but note that some QCanvasPolygonalItem subclasses only use the brush, ignoring the pen setting.

The polygonal item can be drawn on a painter with draw(). Subclasses must reimplement drawShape() to draw themselves.

Like any other canvas item polygonal items can be moved with QCanvasItem::move() and QCanvasItem::moveBy(), or by setting coordinates with QCanvasItem::setX(), QCanvasItem::setY() and QCanvasItem::setZ().

See also Graphics Classes and Image Processing Classes.


Member Function Documentation

QCanvasPolygonalItem::QCanvasPolygonalItem ( QCanvas * canvas )

Constructs a QCanvasPolygonalItem on the canvas canvas.

QCanvasPolygonalItem::~QCanvasPolygonalItem () [virtual]

Note that all subclasses must call hide() in their destructor since hide() needs to be able to access areaPoints().

QPointArray QCanvasPolygonalItem::areaPoints () const [pure virtual]

This function must be reimplemented by subclasses. It must return the points bounding (i.e. outside and not touching) the shape or drawing errors will occur.

Reimplemented in QCanvasPolygon.

QPointArray QCanvasPolygonalItem::areaPointsAdvanced () const [virtual]

Returns the points the polygonal item will have after QCanvasItem::advance(1) is called, i.e. what the points are when advanced by the current xVelocity() and yVelocity().

QRect QCanvasPolygonalItem::boundingRect () const [virtual]

Returns the bounding rectangle of the polygonal item, based on areaPoints().

Reimplemented from QCanvasItem.

QBrush QCanvasPolygonalItem::brush () const

Returns the QBrush used to fill the item, if filled.

See also setBrush().

void QCanvasPolygonalItem::draw ( QPainter & p ) [virtual protected]

Reimplemented from QCanvasItem, this draws the polygonal item by setting the pen and brush for the item on the painter p and calling drawShape().

Reimplemented from QCanvasItem.

void QCanvasPolygonalItem::drawShape ( QPainter & p ) [pure virtual protected]

Subclasses must reimplement this function to draw their shape. The pen and brush of p are already set to pen() and brush() prior to calling this function.

See also draw().

Reimplemented in QCanvasRectangle, QCanvasPolygon, and QCanvasEllipse.

void QCanvasPolygonalItem::invalidate () [protected]

Invalidates all information about the area covered by the canvas item. The item will be updated automatically on the next call that changes the item's status, for example, move() or update(). Call this function if you are going to change the shape of the item (as returned by areaPoints()) while the item is visible.

bool QCanvasPolygonalItem::isValid () const [protected]

Returns TRUE if the polygonal item's area information has been invalidated; otherwise returns FALSE.

See also invalidate().

QPen QCanvasPolygonalItem::pen () const

Returns the QPen used to draw the outline of the item, if any.

See also setPen().

int QCanvasPolygonalItem::rtti () const [virtual]

Returns 2 (QCanvasItem::Rtti_PolygonalItem).

See also QCanvasItem::rtti().

Reimplemented from QCanvasItem.

Reimplemented in QCanvasRectangle, QCanvasPolygon, QCanvasLine, and QCanvasEllipse.

void QCanvasPolygonalItem::setBrush ( QBrush b ) [virtual]

Sets the QBrush used when drawing the polygonal item to the brush b.

See also setPen(), brush(), and drawShape().

Examples: canvas/canvas.cpp and chart/chartform_canvas.cpp.

void QCanvasPolygonalItem::setPen ( QPen p ) [virtual]

Sets the QPen used when drawing the item to the pen p. Note that many QCanvasPolygonalItems do not use the pen value.

See also setBrush(), pen(), and drawShape().

Examples: canvas/canvas.cpp and chart/chartform_canvas.cpp.

void QCanvasPolygonalItem::setWinding ( bool enable ) [protected]

If enable is TRUE, the polygonal item will use the winding algorithm to determine the "inside" of the polygon; otherwise the odd-even algorithm will be used.

The default is to use the odd-even algorithm.

See also winding().

bool QCanvasPolygonalItem::winding () const [protected]

Returns TRUE if the polygonal item uses the winding algorithm to determine the "inside" of the polygon. Returns FALSE if it uses the odd-even algorithm.

The default is to use the odd-even algorithm.

See also setWinding().


This file is part of the Qt toolkit. Copyright © 1995-2003 Trolltech. All Rights Reserved.

Publicité

Best Of

Actualités les plus lues

Semaine
Mois
Année
  1. « Quelque chose ne va vraiment pas avec les développeurs "modernes" », un développeur à "l'ancienne" critique la multiplication des bibliothèques 85
  2. Apercevoir la troisième dimension ou l'utilisation multithreadée d'OpenGL dans Qt, un article des Qt Quarterly traduit par Guillaume Belz 0
  3. Les développeurs ignorent-ils trop les failles découvertes dans leur code ? Prenez-vous en compte les remarques des autres ? 17
  4. Pourquoi les programmeurs sont-ils moins payés que les gestionnaires de programmes ? Manquent-ils de pouvoir de négociation ? 19
  5. BlackBerry 10 : premières images du prochain OS de RIM qui devrait intégrer des widgets et des tuiles inspirées de Windows Phone 0
  6. Quelles nouveautés de C++11 Visual C++ doit-il rapidement intégrer ? Donnez-nous votre avis 10
  7. Adieu qmake, bienvenue qbs : Qt Building Suite, un outil déclaratif et extensible pour la compilation de projets Qt 17
Page suivante

Le blog Digia au hasard

Logo

Déploiement d'applications Qt Commercial sur les tablettes Windows 8

Le blog Digia est l'endroit privilégié pour la communication sur l'édition commerciale de Qt, où des réponses publiques sont apportées aux questions les plus posées au support. Lire l'article.

Communauté

Ressources

Liens utiles

Contact

  • Vous souhaitez rejoindre la rédaction ou proposer un tutoriel, une traduction, une question... ? Postez dans le forum Contribuez ou contactez-nous par MP ou par email (voir en bas de page).

Qt dans le magazine

Cette page est une traduction d'une page de la documentation de Qt, écrite par Nokia Corporation and/or its subsidiary(-ies). Les éventuels problèmes résultant d'une mauvaise traduction ne sont pas imputables à Nokia. Qt 3.2
Copyright © 2012 Developpez LLC. Tous droits réservés Developpez LLC. Aucune reproduction, même partielle, ne peut être faite de ce site et de l'ensemble de son contenu : textes, documents et images sans l'autorisation expresse de Developpez LLC. Sinon, vous encourez selon la loi jusqu'à 3 ans de prison et jusqu'à 300 000 E de dommages et intérêts. Cette page est déposée à la SACD.
Vous avez déniché une erreur ? Un bug ? Une redirection cassée ? Ou tout autre problème, quel qu'il soit ? Ou bien vous désirez participer à ce projet de traduction ? N'hésitez pas à nous contacter ou par MP !
 
 
 
 
Partenaires

Hébergement Web