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The 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.
Note to Qt Desktop Light Edition users: This class is only available in the Qt Desktop Edition.
Inherits Q3ScrollView.
The 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 and QPainter::setWorldMatrix().
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.
Constructs a Q3CanvasView 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 Q3CanvasView is currently showing.
See also setCanvas().
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.
Reimplemented from Q3ScrollView.
Returns a reference to the inverse of the canvas view's current transformation matrix.
See also setWorldMatrix() and worldMatrix().
Sets the canvas that the Q3CanvasView is showing to the canvas canvas.
See also canvas().
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().
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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