Wt::WVirtualImage Class Reference

An abstract widget that shows a viewport to a virtually large image. More...

#include <Wt/WVirtualImage>

Inheritance diagram for Wt::WVirtualImage:

Inheritance graph
[legend]

List of all members.

Public Member Functions

 WVirtualImage (int viewPortWidth, int viewPortHeight, long long imageWidth, long long imageHeight, int gridImageSize=256, WContainerWidget *parent=0)
 Construct a viewport for a virtual image.
 ~WVirtualImage ()
 Destructor.
void redrawAll ()
 Regenerate and redraw the image pieces.
void enableDragging ()
 Enable mouse dragging to scroll around the image.
void scroll (long long dx, long long dy)
 Scroll the viewport of the image over a distance.
void scrollTo (long long x, long long y)
 Scroll the viewport of the image to a specific coordinate.
long long imageWidth () const
 Return the virtual image width.
long long imageHeight () const
 Return the virtual image height.
void resizeImage (long long w, long long h)
 Resize the virtual image.
int viewPortWidth () const
 Return the viewport width.
int viewPortHeight () const
 Return the viewport height.
int gridImageSize () const
 Returns the pieceSize.
long long currentTopLeftX () const
 Returns the current top left X coordinate.
long long currentTopLeftY () const
 Returns the current top left Y coordinate.
long long currentBottomRightX () const
 Returns the current bottom right X coordinate.
long long currentBottomRightY () const
 Returns the current bottom right Y coordinate.

Public Attributes

Signal< long long,
long long > 
viewPortChanged
 Signal emitted whenever the viewport changes.

Static Public Attributes

static const long long Infinite = std::numeric_limits<long long>::max()
 Special value for imageWidth or imageHeight.

Private Member Functions

virtual WImagecreateImage (long long x, long long y, int width, int height)
 Create a grid image for the given rectangle.
virtual WResourcerender (long long x, long long y, int width, int height)
 Render a grid image for the given rectangle.


Detailed Description

An abstract widget that shows a viewport to a virtually large image.

WVirtualImage is an abstract class which renders a large image in small pieces. The large image is broken down, and rendered as a grid of smaller square images parts.

The WVirtualImage may provide interactive navigation using the mouse, by reacting to dragging of the mouse on the image.

The WVirtualImage renders pieces in and bordering the current viewport. In this way, provided the individual pieces load sufficiently fast, the user has effectively the impression of scrolling through a single large image, without glitches. Whenever the image is navigated, if necessary, new images are rendered to maintain the border. Images that are too far from the current viewport are pruned away, so that browser memory remains bounded.

To use this class, you must reimplement one of two virtual methods to specify the contents of each grid piece. Either you provide a suitable WImage for every grid piece, or you provide a WResource which renders the contents for a WImage for every grid piece.

The total image dimensions are (0, 0) to (imageWidth, imageHeight) for a finite image, and become unbounded (including negative numbers) for each dimension which is Infinite.


Constructor & Destructor Documentation

Wt::WVirtualImage::WVirtualImage ( int  viewPortWidth,
int  viewPortHeight,
long long  imageWidth,
long long  imageHeight,
int  gridImageSize = 256,
WContainerWidget parent = 0 
)

Construct a viewport for a virtual image.

You must specify the size of the viewport, and the size of the virtual image. The latter dimensions may be the special value Infinite, indicating that in one or more dimensions, the image size is infinite (in practice limited by MAXINT).

In addition, you must specify the size of each square grid item. The default is 256 by 256.


Member Function Documentation

void Wt::WVirtualImage::redrawAll (  ) 

Regenerate and redraw the image pieces.

This method invalidates all current grid images, and recreates them.

void Wt::WVirtualImage::enableDragging (  ) 

Enable mouse dragging to scroll around the image.

The cursor is changed to a 'move' symbol to indicate the interactivity.

void Wt::WVirtualImage::scroll ( long long  dx,
long long  dy 
)

Scroll the viewport of the image over a distance.

Scroll the viewport over the image over an indicated distance.

void Wt::WVirtualImage::scrollTo ( long long  x,
long long  y 
)

Scroll the viewport of the image to a specific coordinate.

Scroll the viewport so that its top left coordinate becomes (x, y).

WImage * Wt::WVirtualImage::createImage ( long long  x,
long long  y,
int  width,
int  height 
) [private, virtual]

Create a grid image for the given rectangle.

Create the image which spans image coordinates with left upper corner (x, y) and given width and height.

Width and height will not necesarilly equal gridImageSize(), if the the image is not infinite sized.

The default implementation calls render() and creates an image for the resource returned.

You should override this method if you wish to serve for example static image content.

See also:
render()

WResource * Wt::WVirtualImage::render ( long long  x,
long long  y,
int  width,
int  height 
) [private, virtual]

Render a grid image for the given rectangle.

Returns a resource that streams an image which renders the rectangle which spans image coordinates with left upper corner (x, y) and given width and height.

Width and height will not necesarilly equal gridImageSize(), if the the image is not infinite sized.

The default implementation throws an Exception. You must reimplement this method unless you reimplement createImage().

See also:
createImage()


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