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  ·  Toutes les fonctions  ·  Vues d'ensemble  · 

QGraphicsAnchorLayout Class Reference
[QtGui module]

The QGraphicsAnchorLayout class provides a layout where one can anchor widgets together in Graphics View. More...

 #include <QGraphicsAnchorLayout>

Inherits QGraphicsLayout.

This class was introduced in Qt 4.6.


Public Functions

QGraphicsAnchorLayout ( QGraphicsLayoutItem * parent = 0 )
virtual ~QGraphicsAnchorLayout ()
QGraphicsAnchor * addAnchor ( QGraphicsLayoutItem * firstItem, Qt::AnchorPoint firstEdge, QGraphicsLayoutItem * secondItem, Qt::AnchorPoint secondEdge )
void addAnchors ( QGraphicsLayoutItem * firstItem, QGraphicsLayoutItem * secondItem, Qt::Orientations orientations = Qt::Horizontal | Qt::Vertical )
void addCornerAnchors ( QGraphicsLayoutItem * firstItem, Qt::Corner firstCorner, QGraphicsLayoutItem * secondItem, Qt::Corner secondCorner )
QGraphicsAnchor * anchor ( QGraphicsLayoutItem * firstItem, Qt::AnchorPoint firstEdge, QGraphicsLayoutItem * secondItem, Qt::AnchorPoint secondEdge )
qreal horizontalSpacing () const
void setHorizontalSpacing ( qreal spacing )
void setSpacing ( qreal spacing )
void setVerticalSpacing ( qreal spacing )
qreal verticalSpacing () const

Reimplemented Public Functions

virtual int count () const
virtual void invalidate ()
virtual QGraphicsLayoutItem * itemAt ( int index ) const
virtual void removeAt ( int index )
virtual void setGeometry ( const QRectF & geom )

Reimplemented Protected Functions

virtual QSizeF sizeHint ( Qt::SizeHint which, const QSizeF & constraint = QSizeF() ) const

Detailed Description

The QGraphicsAnchorLayout class provides a layout where one can anchor widgets together in Graphics View.

The anchor layout allows developers to specify how widgets should be placed relative to each other, and to the layout itself. The specification is made by adding anchors to the layout by calling addAnchor(), addAnchors() or addCornerAnchors().

Existing anchors in the layout can be accessed with the anchor() function. Items that are anchored are automatically added to the layout, and if items are removed, all their anchors will be automatically removed.

Using an anchor layout to align simple colored widgets.

Anchors are always set up between edges of an item, where the "center" is also considered to be an edge. Consider the following example:

     layout->addAnchor(b, Qt::AnchorLeft, a, Qt::AnchorRight);
     layout->addAnchor(b, Qt::AnchorTop, a, Qt::AnchorBottom);

Here, the right edge of item a is anchored to the left edge of item b and the bottom edge of item a is anchored to the top edge of item b, with the result that item b will be placed diagonally to the right and below item b.

The addCornerAnchors() function provides a simpler way of anchoring the corners of two widgets than the two individual calls to addAnchor() shown in the code above. Here, we see how a widget can be anchored to the top-left corner of the enclosing layout:

     layout->addCornerAnchors(a, Qt::TopLeftCorner, layout, Qt::TopLeftCorner);

In cases where anchors are used to match the widths or heights of widgets, it is convenient to use the addAnchors() function. As with the other functions for specifying anchors, it can also be used to anchor a widget to a layout.


Size Hints and Size Policies in an Anchor Layout

QGraphicsAnchorLayout respects each item's size hints and size policies. Note that there are some properties of QSizePolicy that are not respected.

Spacing within an Anchor Layout

The layout may distribute some space between the items. If the spacing has not been explicitly specified, the actual amount of space will usually be 0.

However, if the first edge is the opposite of the second edge (e.g., the right edge of the first widget is anchored to the left edge of the second widget), the size of the anchor will be queried from the style through a pixel metric: PM_LayoutHorizontalSpacing for horizontal anchors and PM_LayoutVerticalSpacing for vertical anchors.

If the spacing is negative, the items will overlap to some extent.

Known issues

There are some features that QGraphicsAnchorLayout currently does not support. This might change in the future, so avoid using these features if you want to avoid any future regressions in behaviour:

See also QGraphicsLinearLayout, QGraphicsGridLayout, and QGraphicsLayout.


Member Function Documentation

QGraphicsAnchorLayout::QGraphicsAnchorLayout ( QGraphicsLayoutItem * parent = 0 )

Constructs a QGraphicsAnchorLayout instance. parent is passed to QGraphicsLayout's constructor.

QGraphicsAnchorLayout::~QGraphicsAnchorLayout ()   [virtual]

Destroys the QGraphicsAnchorLayout object.

QGraphicsAnchor * QGraphicsAnchorLayout::addAnchor ( QGraphicsLayoutItem * firstItem, Qt::AnchorPoint firstEdge, QGraphicsLayoutItem * secondItem, Qt::AnchorPoint secondEdge )

Creates an anchor between the edge firstEdge of item firstItem and the edge secondEdge of item secondItem. The spacing of the anchor is picked up from the style. Anchors between a layout edge and an item edge will have a size of 0. If there is already an anchor between the edges, the the new anchor will replace the old one.

firstItem and secondItem are automatically added to the layout if they are not part of the layout. This means that count() can increase by up to 2.

The spacing an anchor will get depends on the type of anchor. For instance, anchors from the Right edge of one item to the Left edge of another (or vice versa) will use the default horizontal spacing. The same behaviour applies to Bottom to Top anchors, (but they will use the default vertical spacing). For all other anchor combinations, the spacing will be 0. All anchoring functions will follow this rule.

The spacing can also be set manually by using QGraphicsAnchor::setSpacing() method.

Calling this function where firstItem or secondItem are ancestors of the layout have undefined behaviour.

See also addAnchors() and addCornerAnchors().

void QGraphicsAnchorLayout::addAnchors ( QGraphicsLayoutItem * firstItem, QGraphicsLayoutItem * secondItem, Qt::Orientations orientations = Qt::Horizontal | Qt::Vertical )

Anchors two or four edges of firstItem with the corresponding edges of secondItem, so that firstItem has the same size as secondItem in the dimensions specified by orientations.

For example, the following example anchors the left and right edges of two items to match their widths:

     layout->addAnchor(b, Qt::AnchorLeft, c, Qt::AnchorLeft);
     layout->addAnchor(b, Qt::AnchorRight, c, Qt::AnchorRight);

This can also be achieved using the following line of code:

     layout->addAnchors(b, c, Qt::Horizontal);

See also addAnchor() and addCornerAnchors().

void QGraphicsAnchorLayout::addCornerAnchors ( QGraphicsLayoutItem * firstItem, Qt::Corner firstCorner, QGraphicsLayoutItem * secondItem, Qt::Corner secondCorner )

Creates two anchors between firstItem and secondItem specified by the corners, firstCorner and secondCorner, where one is for the horizontal edge and another one for the vertical edge.

This is a convenience function, since anchoring corners can be expressed as anchoring two edges. For instance:

     layout->addAnchor(a, Qt::AnchorTop, layout, Qt::AnchorTop);
     layout->addAnchor(a, Qt::AnchorLeft, layout, Qt::AnchorLeft);

This can also be achieved with the following line of code:

     layout->addCornerAnchors(a, Qt::TopLeftCorner, layout, Qt::TopLeftCorner);

If there is already an anchor between the edge pairs, it will be replaced by the anchors that this function specifies.

firstItem and secondItem are automatically added to the layout if they are not part of the layout. This means that count() can increase by up to 2.

See also addAnchor() and addAnchors().

QGraphicsAnchor * QGraphicsAnchorLayout::anchor ( QGraphicsLayoutItem * firstItem, Qt::AnchorPoint firstEdge, QGraphicsLayoutItem * secondItem, Qt::AnchorPoint secondEdge )

Returns the anchor between the anchor points defined by firstItem and firstEdge and secondItem and secondEdge. If there is no such anchor, the function will return 0.

int QGraphicsAnchorLayout::count () const   [virtual]

Reimplemented from QGraphicsLayout::count().

qreal QGraphicsAnchorLayout::horizontalSpacing () const

Returns the default horizontal spacing for the anchor layout.

See also verticalSpacing() and setHorizontalSpacing().

void QGraphicsAnchorLayout::invalidate ()   [virtual]

Reimplemented from QGraphicsLayout::invalidate().

QGraphicsLayoutItem * QGraphicsAnchorLayout::itemAt ( int index ) const   [virtual]

Reimplemented from QGraphicsLayout::itemAt().

void QGraphicsAnchorLayout::removeAt ( int index )   [virtual]

Reimplemented from QGraphicsLayout::removeAt().

Removes the layout item at index without destroying it. Ownership of the item is transferred to the caller.

Removing an item will also remove any of the anchors associated with it.

See also itemAt() and count().

void QGraphicsAnchorLayout::setGeometry ( const QRectF & geom )   [virtual]

Reimplemented from QGraphicsLayoutItem::setGeometry().

void QGraphicsAnchorLayout::setHorizontalSpacing ( qreal spacing )

Sets the default horizontal spacing for the anchor layout to spacing.

See also horizontalSpacing(), setVerticalSpacing(), and setSpacing().

void QGraphicsAnchorLayout::setSpacing ( qreal spacing )

Sets the default horizontal and the default vertical spacing for the anchor layout to spacing.

If an item is anchored with no spacing associated with the anchor, it will use the default spacing.

QGraphicsAnchorLayout does not support negative spacings. Setting a negative value will unset the previous spacing and make the layout use the spacing provided by the current widget style.

See also setHorizontalSpacing() and setVerticalSpacing().

void QGraphicsAnchorLayout::setVerticalSpacing ( qreal spacing )

Sets the default vertical spacing for the anchor layout to spacing.

See also verticalSpacing(), setHorizontalSpacing(), and setSpacing().

QSizeF QGraphicsAnchorLayout::sizeHint ( Qt::SizeHint which, const QSizeF & constraint = QSizeF() ) const   [virtual protected]

Reimplemented from QGraphicsLayoutItem::sizeHint().

qreal QGraphicsAnchorLayout::verticalSpacing () const

Returns the default vertical spacing for the anchor layout.

See also horizontalSpacing() and setVerticalSpacing().

Publicité

Best Of

Actualités les plus lues

Semaine
Mois
Année
  1. Microsoft ouvre aux autres compilateurs C++ AMP, la spécification pour la conception d'applications parallèles C++ utilisant le GPU 22
  2. Les développeurs ignorent-ils trop les failles découvertes dans leur code ? Prenez-vous en compte les remarques des autres ? 17
  3. RIM : « 13 % des développeurs ont gagné plus de 100 000 $ sur l'AppWord », Qt et open-source au menu du BlackBerry DevCon Europe 0
  4. « Quelque chose ne va vraiment pas avec les développeurs "modernes" », un développeur à "l'ancienne" critique la multiplication des bibliothèques 12
  5. BlackBerry 10 : premières images du prochain OS de RIM qui devrait intégrer des widgets et des tuiles inspirées de Windows Phone 0
  6. Adieu qmake, bienvenue qbs : Qt Building Suite, un outil déclaratif et extensible pour la compilation de projets Qt 17
  7. Quelles nouveautés de C++11 Visual C++ doit-il rapidement intégrer ? Donnez-nous votre avis 10
Page suivante

Le Qt Developer Network au hasard

Logo

La création de colonnes dans une ListView en QML

Le Qt Developer Network est un réseau de développeurs Qt anglophone, où ils peuvent partager leur expérience sur le framework. 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 4.6
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