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The QtCanvasView class provides an on-screen view of a QtCanvas. More...
#include <QtCanvasView>
Inherits QScrollArea.
The QtCanvasView class provides an on-screen view of a QtCanvas.
A QtCanvasView is widget which provides a view of a QtCanvas.
If you want users to be able to interact with a canvas view, subclass QtCanvasView. You might then reimplement QtScrollView::contentsMousePressEvent(). For example:
void MyCanvasView::contentsMousePressEvent(QMouseEvent* e) { QtCanvasItemList l = canvas()->collisions(e->pos()); for (QtCanvasItemList::Iterator it = l.begin(); it!= l.end(); ++it) { if ((*it)->rtti() == QtCanvasRectangle::RTTI) qDebug("A QtCanvasRectangle 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().
This property holds whether high quality rendering is turned on.
If high quality rendering is turned on, the canvas view will paint itself using the QPainter::Antialiasing and QPainter::SmoothPixmapTransform rendering flags.
Enabling these flag will usually improve the visual appearance on the screen at the cost of rendering speed.
Access functions:
Constructs a QtCanvasView with parent parent. The canvas view is not associated with a canvas, so you must to call setCanvas() to view a canvas.
Constructs a QtCanvasView which views canvas canvas, with parent parent.
Destroys the canvas view. The associated canvas is not deleted.
Returns a pointer to the canvas which the QtCanvasView is currently showing.
See also setCanvas().
Repaints part of the QtCanvas 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.
Returns a reference to the inverse of the canvas view's current transformation matrix.
See also setWorldMatrix() and worldMatrix().
Sets the canvas that the QtCanvasView is showing to the canvas canvas.
See also canvas().
Sets the transformation matrix of the QtCanvasView 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 QtCanvasView 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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