Q3CanvasView Class ReferenceThe Q3CanvasView class provides an on-screen view of a Q3Canvas. More... #include <Q3CanvasView> This class is part of the Qt 3 support library. It is provided to keep old source code working. We strongly advise against using it in new code. See Porting to Qt 4 for more information. Inherits Q3ScrollView. Public Functions
Reimplemented Protected Functions
Additional Inherited Members
Detailed DescriptionThe Q3CanvasView class provides an on-screen view of a Q3Canvas. A Q3CanvasView is widget which provides a view of a Q3Canvas. If you want users to be able to interact with a canvas view, subclass Q3CanvasView. You might then reimplement Q3ScrollView::contentsMousePressEvent(). For example: void MyCanvasView::contentsMousePressEvent(QMouseEvent* e) { Q3CanvasItemList l = canvas()->collisions(e->pos()); for (Q3CanvasItemList::Iterator it=l.begin(); it!=l.end(); ++it) { if ((*it)->rtti() == Q3CanvasRectangle::RTTI) qDebug("A Q3CanvasRectangle lies somewhere at this point"); } } The canvas view shows canvas canvas(); this can be changed using setCanvas(). A transformation matrix can be used to transform the view of the canvas in various ways, for example, zooming in or out or rotating. For example: QMatrix wm; wm.scale(2, 2); // Zooms in by 2 times wm.rotate(90); // Rotates 90 degrees counter clockwise // around the origin. wm.translate(0, -canvas->height()); // moves the canvas down so what was visible // before is still visible. myCanvasView->setWorldMatrix(wm); Use setWorldMatrix() to set the canvas view's world matrix: you must ensure that the world matrix is invertible. The current world matrix is retrievable with worldMatrix(), and its inversion is retrievable with inverseWorldMatrix(). Example: The following code finds the part of the canvas that is visible in this view, i.e. the bounding rectangle of the view in canvas coordinates. QRect rc = QRect(myCanvasView->contentsX(), myCanvasView->contentsY(), myCanvasView->visibleWidth(), myCanvasView->visibleHeight()); QRect canvasRect = myCanvasView->inverseWorldMatrix().mapRect(rc); See also QMatrix, QPainter::setWorldMatrix(), QtCanvas, and Porting to Graphics View. Member Function DocumentationQ3CanvasView::Q3CanvasView ( QWidget * parent = 0, const char * name = 0, Qt::WindowFlags f = 0 )Constructs a Q3CanvasView with parent parent, and name name, using the widget flags f. The canvas view is not associated with a canvas, so you must to call setCanvas() to view a canvas. Q3CanvasView::Q3CanvasView ( Q3Canvas * canvas, QWidget * parent = 0, const char * name = 0, Qt::WindowFlags f = 0 )This is an overloaded function. Constructs a Q3CanvasView which views canvas canvas, with parent parent, and name name, using the widget flags f. Q3CanvasView::~Q3CanvasView ()Destroys the canvas view. The associated canvas is not deleted. Q3Canvas * Q3CanvasView::canvas () constReturns a pointer to the canvas which the Q3CanvasView is currently showing. See also setCanvas(). void Q3CanvasView::drawContents ( QPainter * p, int cx, int cy, int cw, int ch ) [virtual protected]Reimplemented from Q3ScrollView::drawContents(). Repaints part of the Q3Canvas that the canvas view is showing starting at cx by cy, with a width of cw and a height of ch using the painter p. const QMatrix & Q3CanvasView::inverseWorldMatrix () constReturns a reference to the inverse of the canvas view's current transformation matrix. See also setWorldMatrix() and worldMatrix(). void Q3CanvasView::setCanvas ( Q3Canvas * canvas )Sets the canvas that the Q3CanvasView is showing to the canvas canvas. See also canvas(). bool Q3CanvasView::setWorldMatrix ( const QMatrix & wm )Sets the transformation matrix of the Q3CanvasView to wm. The matrix must be invertible (i.e. if you create a world matrix that zooms out by 2 times, then the inverse of this matrix is one that will zoom in by 2 times). When you use this, you should note that the performance of the Q3CanvasView will decrease considerably. Returns false if wm is not invertable; otherwise returns true. See also worldMatrix(), inverseWorldMatrix(), and QMatrix::isInvertible(). QSize Q3CanvasView::sizeHint () const [virtual protected]Reimplemented from QWidget::sizeHint(). Suggests a size sufficient to view the entire canvas. const QMatrix & Q3CanvasView::worldMatrix () constReturns a reference to the canvas view's current transformation matrix. See also setWorldMatrix() and inverseWorldMatrix(). X
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