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com.google.gwt.canvas.client
Class Canvas

java.lang.Object
  extended by com.google.gwt.user.client.ui.UIObject
      extended by com.google.gwt.user.client.ui.Widget
          extended by com.google.gwt.user.client.ui.FocusWidget
              extended by com.google.gwt.canvas.client.Canvas
All Implemented Interfaces:
HasAllDragAndDropHandlers, HasAllFocusHandlers, HasAllGestureHandlers, HasAllKeyHandlers, HasAllMouseHandlers, HasAllTouchHandlers, HasBlurHandlers, HasClickHandlers, HasDoubleClickHandlers, HasDragEndHandlers, HasDragEnterHandlers, HasDragHandlers, HasDragLeaveHandlers, HasDragOverHandlers, HasDragStartHandlers, HasDropHandlers, HasFocusHandlers, HasGestureChangeHandlers, HasGestureEndHandlers, HasGestureStartHandlers, HasKeyDownHandlers, HasKeyPressHandlers, HasKeyUpHandlers, HasMouseDownHandlers, HasMouseMoveHandlers, HasMouseOutHandlers, HasMouseOverHandlers, HasMouseUpHandlers, HasMouseWheelHandlers, HasTouchCancelHandlers, HasTouchEndHandlers, HasTouchMoveHandlers, HasTouchStartHandlers, HasAttachHandlers, HasHandlers, EventListener, Focusable, HasEnabled, HasFocus, HasVisibility, IsWidget, SourcesClickEvents, SourcesFocusEvents, SourcesKeyboardEvents, SourcesMouseEvents
public class Canvas
extends FocusWidget

A widget representing a <canvas> element. This widget may not be supported on all browsers.

Nested Class Summary
 
Nested classes/interfaces inherited from class com.google.gwt.user.client.ui.UIObject
UIObject.DebugIdImpl, UIObject.DebugIdImplEnabled
 
Field Summary
 
Fields inherited from class com.google.gwt.user.client.ui.UIObject
DEBUG_ID_PREFIX
 
Method Summary
static Canvas createIfSupported()
          Return a new Canvas if supported, and null otherwise.
 CanvasElement getCanvasElement()
          Returns the attached Canvas Element.
 Context getContext(java.lang.String contextId)
          Gets the rendering context that may be used to draw on this canvas.
 Context2d getContext2d()
          Returns a 2D rendering context.
 int getCoordinateSpaceHeight()
          Gets the height of the internal canvas coordinate space.
 int getCoordinateSpaceWidth()
          Gets the width of the internal canvas coordinate space.
static boolean isSupported()
          Runtime check for whether the canvas element is supported in this browser.
 void setCoordinateSpaceHeight(int height)
          Sets the height of the internal canvas coordinate space.
 void setCoordinateSpaceWidth(int width)
          Sets the width of the internal canvas coordinate space.
 java.lang.String toDataUrl()
          Returns a data URL for the current content of the canvas element.
 java.lang.String toDataUrl(java.lang.String type)
          Returns a data URL for the current content of the canvas element, with a specified type.
static Canvas wrap(CanvasElement element)
          Wrap an existing canvas element.
 
Methods inherited from class com.google.gwt.user.client.ui.FocusWidget
addBlurHandler, addClickHandler, addClickListener, addDoubleClickHandler, addDragEndHandler, addDragEnterHandler, addDragHandler, addDragLeaveHandler, addDragOverHandler, addDragStartHandler, addDropHandler, addFocusHandler, addFocusListener, addGestureChangeHandler, addGestureEndHandler, addGestureStartHandler, addKeyboardListener, addKeyDownHandler, addKeyPressHandler, addKeyUpHandler, addMouseDownHandler, addMouseListener, addMouseMoveHandler, addMouseOutHandler, addMouseOverHandler, addMouseUpHandler, addMouseWheelHandler, addMouseWheelListener, addTouchCancelHandler, addTouchEndHandler, addTouchMoveHandler, addTouchStartHandler, getFocusImpl, getTabIndex, isEnabled, onAttach, removeClickListener, removeFocusListener, removeKeyboardListener, removeMouseListener, removeMouseWheelListener, setAccessKey, setEnabled, setFocus, setTabIndex
 
Methods inherited from class com.google.gwt.user.client.ui.Widget
addAttachHandler, addBitlessDomHandler, addDomHandler, addHandler, asWidget, asWidgetOrNull, createHandlerManager, delegateEvent, doAttachChildren, doDetachChildren, fireEvent, getHandlerCount, getLayoutData, getParent, isAttached, isOrWasAttached, onBrowserEvent, onDetach, onLoad, onUnload, removeFromParent, setLayoutData, sinkEvents, unsinkEvents
 
Methods inherited from class com.google.gwt.user.client.ui.UIObject
addStyleDependentName, addStyleName, ensureDebugId, ensureDebugId, ensureDebugId, getAbsoluteLeft, getAbsoluteTop, getElement, getOffsetHeight, getOffsetWidth, getStyleElement, getStyleName, getStyleName, getStylePrimaryName, getStylePrimaryName, getTitle, isVisible, isVisible, onEnsureDebugId, removeStyleDependentName, removeStyleName, resolvePotentialElement, setElement, setElement, setHeight, setPixelSize, setSize, setStyleDependentName, setStyleName, setStyleName, setStyleName, setStyleName, setStylePrimaryName, setStylePrimaryName, setTitle, setVisible, setVisible, setWidth, sinkBitlessEvent, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface com.google.gwt.event.shared.HasHandlers
fireEvent
 

Method Detail

createIfSupported

public static Canvas createIfSupported()
Return a new Canvas if supported, and null otherwise.

Returns:
a new Canvas if supported, and null otherwise

wrap

public static Canvas wrap(CanvasElement element)
Wrap an existing canvas element. The element must already be attached to the document. If the element is removed from the document, you must call RootPanel.detachNow(Widget). Note: This method can return null if there is no support for canvas by the current browser.

Parameters:
element - the element to wrap
Returns:
the Canvas widget or null if canvas is not supported by the current browser.

isSupported

public static boolean isSupported()
Runtime check for whether the canvas element is supported in this browser.

Returns:
whether the canvas element is supported

getCanvasElement

public CanvasElement getCanvasElement()
Returns the attached Canvas Element.

Returns:
the Canvas Element

getContext

public Context getContext(java.lang.String contextId)
Gets the rendering context that may be used to draw on this canvas.

Parameters:
contextId - the context id as a String
Returns:
the canvas rendering context

getContext2d

public Context2d getContext2d()
Returns a 2D rendering context. This is a convenience method, see getContext(String).

Returns:
a 2D canvas rendering context

getCoordinateSpaceHeight

public int getCoordinateSpaceHeight()
Gets the height of the internal canvas coordinate space.

Returns:
the height, in pixels
See Also:
setCoordinateSpaceHeight(int)

getCoordinateSpaceWidth

public int getCoordinateSpaceWidth()
Gets the width of the internal canvas coordinate space.

Returns:
the width, in pixels
See Also:
setCoordinateSpaceWidth(int)

setCoordinateSpaceHeight

public void setCoordinateSpaceHeight(int height)
Sets the height of the internal canvas coordinate space.

Parameters:
height - the height, in pixels
See Also:
getCoordinateSpaceHeight()

setCoordinateSpaceWidth

public void setCoordinateSpaceWidth(int width)
Sets the width of the internal canvas coordinate space.

Parameters:
width - the width, in pixels
See Also:
getCoordinateSpaceWidth()

toDataUrl

public java.lang.String toDataUrl()
Returns a data URL for the current content of the canvas element.

Returns:
a data URL for the current content of this element.

toDataUrl

public java.lang.String toDataUrl(java.lang.String type)
Returns a data URL for the current content of the canvas element, with a specified type.

Parameters:
type - the type of the data url, e.g., image/jpeg or image/png.
Returns:
a data URL for the current content of this element with the specified type.
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