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< td align = "right" valign = "center" > < img src = "logo32.png" align = "right" width = "64" height = "32" border = "0" > < / td > < / tr > < / table > < h1 align = center > TQCanvasView Class Reference< br > < small > [< a href = "canvas.html" > canvas module< / a > ]< / small > < / h1 >
< p > The TQCanvasView class provides an on-screen view of a TQCanvas.
< a href = "#details" > More...< / a >
< p > < tt > #include < < a href = "qcanvas-h.html" > ntqcanvas.h< / a > > < / tt >
< p > Inherits < a href = "ntqscrollview.html" > TQScrollView< / a > .
< p > < a href = "qcanvasview-members.html" > List of all member functions.< / a >
< h2 > Public Members< / h2 >
< ul >
< li class = fn > < a href = "#TQCanvasView" > < b > TQCanvasView< / b > < / a > ( TQWidget * parent = 0, const char * name = 0, WFlags f = 0 )< / li >
< li class = fn > < a href = "#TQCanvasView-2" > < b > TQCanvasView< / b > < / a > ( TQCanvas * canvas, TQWidget * parent = 0, const char * name = 0, WFlags f = 0 )< / li >
< li class = fn > < a href = "#~TQCanvasView" > < b > ~TQCanvasView< / b > < / a > ()< / li >
< li class = fn > TQCanvas * < a href = "#canvas" > < b > canvas< / b > < / a > () const< / li >
< li class = fn > void < a href = "#setCanvas" > < b > setCanvas< / b > < / a > ( TQCanvas * canvas )< / li >
< li class = fn > const TQWMatrix & < a href = "#worldMatrix" > < b > worldMatrix< / b > < / a > () const< / li >
< li class = fn > const TQWMatrix & < a href = "#inverseWorldMatrix" > < b > inverseWorldMatrix< / b > < / a > () const< / li >
< li class = fn > bool < a href = "#setWorldMatrix" > < b > setWorldMatrix< / b > < / a > ( const TQWMatrix & wm )< / li >
< / ul >
< h2 > Protected Members< / h2 >
< ul >
< li class = fn > virtual void < a href = "#drawContents" > < b > drawContents< / b > < / a > ( TQPainter * p, int cx, int cy, int cw, int ch )< / li >
< li class = fn > virtual TQSize < a href = "#sizeHint" > < b > sizeHint< / b > < / a > () const< / li >
< / ul >
< hr > < a name = "details" > < / a > < h2 > Detailed Description< / h2 >
The TQCanvasView class provides an on-screen view of a < a href = "ntqcanvas.html" > TQCanvas< / a > .
< p >
< p > A TQCanvasView is widget which provides a view of a TQCanvas.
< p > If you want users to be able to interact with a canvas view,
subclass TQCanvasView. You might then reimplement
< a href = "ntqscrollview.html#contentsMousePressEvent" > TQScrollView::contentsMousePressEvent< / a > (). For example, assuming no
< a href = "ntqwmatrix.html#TransformationMode" > transformation matrix< / a > is set:
< p > < pre >
void MyCanvasView::contentsMousePressEvent( < a href = "qmouseevent.html" > TQMouseEvent< / a > * e )
{
< a href = "qcanvasitemlist.html" > TQCanvasItemList< / a > l = < a href = "#canvas" > canvas< / a > ()-> collisions(e-> < a href = "qmouseevent.html#pos" > pos< / a > ());
for (TQCanvasItemList::Iterator it=l.< a href = "ntqvaluelist.html#begin" > begin< / a > (); it!=l.< a href = "ntqvaluelist.html#end" > end< / a > (); ++it) {
if ( (*it)-> rtti() == TQCanvasRectangle::RTTI )
< a href = "ntqapplication.html#qDebug" > tqDebug< / a > ("A TQCanvasRectangle lies somewhere at this point");
}
}
< / pre >
< p > The canvas view shows canvas < a href = "#canvas" > canvas< / a > (); this can be changed using
< a href = "#setCanvas" > setCanvas< / a > ().
< p > 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:
< p > < pre >
< a href = "ntqwmatrix.html" > TQWMatrix< / a > wm;
wm.< a href = "ntqwmatrix.html#scale" > scale< / a > ( 2, 2 ); // Zooms in by 2 times
wm.< a href = "ntqwmatrix.html#rotate" > rotate< / a > ( 90 ); // Rotates 90 degrees counter clockwise
// around the origin.
wm.< a href = "ntqwmatrix.html#translate" > translate< / a > ( 0, -canvas-> height() );
// moves the canvas down so what was visible
// before is still visible.
myCanvasView-> setWorldMatrix( wm );
< / pre >
< p > Use < a href = "#setWorldMatrix" > setWorldMatrix< / a > () to set the canvas view's world matrix: you must
ensure that the world matrix is invertible. The current world matrix
is retrievable with < a href = "#worldMatrix" > worldMatrix< / a > (), and its inversion is retrievable
with < a href = "#inverseWorldMatrix" > inverseWorldMatrix< / a > ().
< p > Example:
< p > 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.
< p > < pre >
< a href = "ntqrect.html" > TQRect< / a > rc = TQRect( myCanvasView-> contentsX(), myCanvasView-> contentsY(),
myCanvasView-> visibleWidth(), myCanvasView-> visibleHeight() );
< a href = "ntqrect.html" > TQRect< / a > canvasRect = myCanvasView-> inverseWorldMatrix().mapRect(rc);
< / pre >
< p > < p > See also < a href = "ntqwmatrix.html" > TQWMatrix< / a > , < a href = "ntqpainter.html#setWorldMatrix" > TQPainter::setWorldMatrix< / a > (), < a href = "graphics.html" > Graphics Classes< / a > , and < a href = "images.html" > Image Processing Classes< / a > .
< p >
< hr > < h2 > Member Function Documentation< / h2 >
< h3 class = fn > < a name = "TQCanvasView" > < / a > TQCanvasView::TQCanvasView ( < a href = "ntqwidget.html" > TQWidget< / a > * parent = 0, const char * name = 0, WFlags f = 0 )
< / h3 >
Constructs a TQCanvasView with parent < em > parent< / em > , and name < em > name< / em > ,
using the widget flags < em > f< / em > . The canvas view is not associated
with a canvas, so you must to call < a href = "#setCanvas" > setCanvas< / a > () to view a
canvas.
< h3 class = fn > < a name = "TQCanvasView-2" > < / a > TQCanvasView::TQCanvasView ( < a href = "ntqcanvas.html" > TQCanvas< / a > * canvas, < a href = "ntqwidget.html" > TQWidget< / a > * parent = 0, const char * name = 0, WFlags f = 0 )
< / h3 >
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
< p > Constructs a TQCanvasView which views canvas < em > canvas< / em > , with parent
< em > parent< / em > , and name < em > name< / em > , using the widget flags < em > f< / em > .
< h3 class = fn > < a name = "~TQCanvasView" > < / a > TQCanvasView::~TQCanvasView ()
< / h3 >
Destroys the canvas view. The associated canvas is < em > not< / em > deleted.
< h3 class = fn > < a href = "ntqcanvas.html" > TQCanvas< / a > * < a name = "canvas" > < / a > TQCanvasView::canvas () const
< / h3 >
< p > Returns a pointer to the canvas which the TQCanvasView is currently
showing.
< h3 class = fn > void < a name = "drawContents" > < / a > TQCanvasView::drawContents ( < a href = "ntqpainter.html" > TQPainter< / a > * p, int cx, int cy, int cw, int ch )< tt > [virtual protected]< / tt >
< / h3 >
Repaints part of the < a href = "ntqcanvas.html" > TQCanvas< / a > that the canvas view is showing
starting at < em > cx< / em > by < em > cy< / em > , with a width of < em > cw< / em > and a height of < em > ch< / em > using the painter < em > p< / em > .
< p > < b > Warning:< / b > When double buffering is enabled, < a href = "#drawContents" > drawContents< / a > () will
not respect the current settings of the painter when setting up
the painter for the double buffer (e.g., < a href = "ntqscrollview.html#viewport" > viewport< / a > () and
window()). Also, be aware that < a href = "ntqcanvas.html#update" > TQCanvas::update< / a > () bypasses
drawContents(), which means any reimplementation of
drawContents() is not called.
< p > < p > See also < a href = "ntqcanvas.html#setDoubleBuffering" > TQCanvas::setDoubleBuffering< / a > ().
< p > Reimplemented from < a href = "ntqscrollview.html#drawContents" > TQScrollView< / a > .
< h3 class = fn > const < a href = "ntqwmatrix.html" > TQWMatrix< / a > & < a name = "inverseWorldMatrix" > < / a > TQCanvasView::inverseWorldMatrix () const
< / h3 >
Returns a reference to the inverse of the canvas view's current
< a href = "ntqwmatrix.html#TransformationMode" > transformation matrix< / a > .
< p > < p > See also < a href = "#setWorldMatrix" > setWorldMatrix< / a > () and < a href = "#worldMatrix" > worldMatrix< / a > ().
< h3 class = fn > void < a name = "setCanvas" > < / a > TQCanvasView::setCanvas ( < a href = "ntqcanvas.html" > TQCanvas< / a > * canvas )
< / h3 >
Sets the canvas that the TQCanvasView is showing to the canvas < em > canvas< / em > .
< h3 class = fn > bool < a name = "setWorldMatrix" > < / a > TQCanvasView::setWorldMatrix ( const < a href = "ntqwmatrix.html" > TQWMatrix< / a > & wm )
< / h3 >
Sets the < a href = "ntqwmatrix.html#TransformationMode" > transformation matrix< / a > of the TQCanvasView to < em > wm< / em > . 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).
< p > When you use this, you should note that the performance of the
TQCanvasView will decrease considerably.
< p > Returns FALSE if < em > wm< / em > is not invertable; otherwise returns TRUE.
< p > < p > See also < a href = "#worldMatrix" > worldMatrix< / a > (), < a href = "#inverseWorldMatrix" > inverseWorldMatrix< / a > (), and < a href = "ntqwmatrix.html#isInvertible" > TQWMatrix::isInvertible< / a > ().
< p > Example: < a href = "canvas-example.html#x2930" > canvas/canvas.cpp< / a > .
< h3 class = fn > < a href = "ntqsize.html" > TQSize< / a > < a name = "sizeHint" > < / a > TQCanvasView::sizeHint () const< tt > [virtual protected]< / tt >
< / h3 >
Suggests a size sufficient to view the entire canvas.
< h3 class = fn > const < a href = "ntqwmatrix.html" > TQWMatrix< / a > & < a name = "worldMatrix" > < / a > TQCanvasView::worldMatrix () const
< / h3 >
Returns a reference to the canvas view's current < a href = "ntqwmatrix.html#TransformationMode" > transformation matrix< / a > .
< p > < p > See also < a href = "#setWorldMatrix" > setWorldMatrix< / a > () and < a href = "#inverseWorldMatrix" > inverseWorldMatrix< / a > ().
< p > Example: < a href = "canvas-example.html#x2931" > canvas/canvas.cpp< / a > .
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