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The QCanvasView class provides an on-screen view of a QCanvas. More...
#include <QCanvasView>
This class is part of the Qt 3 compatibility library. It is provided to keep old source code working. We strongly advise against using it in new code.
Inherits QScrollView.
The QCanvasView class provides an on-screen view of a QCanvas.
If you want users to be able to interact with a canvas view, you will need to subclass QCanvasView. You might then reimplement some of the event handlers, for example, QScrollView::contentsMousePressEvent():
void MyCanvasView::contentsMousePressEvent(QMouseEvent* evt) { QCanvasItemList lst = canvas()->collisions(evt->pos()); QCanvasItemList::ConstIterator i = lst.constBegin(); for (; i != lst.constEnd(); ++i) { if ((*i)->rtti() == QCanvasRectangle::RTTI) qDebug("A QCanvasRectangle 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:
QWMatrix 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 QWMatrix and QPainter::setWorldMatrix().
Constructs a QCanvasView 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.
Constructs a QCanvasView which views canvas canvas, with parent parent, and name name, using the widget flags f.
Destroys the canvas view. The associated canvas is not deleted.
Returns a pointer to the canvas which the QCanvasView is currently showing.
Repaints part of the QCanvas 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.
Reimplemented from QScrollView.
Returns a reference to the inverse of the canvas view's current transformation matrix.
See also setWorldMatrix() and worldMatrix().
Sets the canvas that the QCanvasView is showing to the canvas canvas.
Sets the transformation matrix of the QCanvasView 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).
Using this function will considerably reduce the speed of the canvas view.
Returns false if wm is not invertable; otherwise returns true.
See also worldMatrix(), inverseWorldMatrix(), and QWMatrix::isInvertible().
Suggests a size sufficient to view the entire canvas.
Reimplemented from QWidget.
Returns a reference to the canvas view's current transformation matrix.
See also setWorldMatrix() and inverseWorldMatrix().
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