Canvas (GWT Javadoc)

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## com.google.gwt.canvas.client
Class Canvas

    java.lang.Object
      com.google.gwt.user.client.ui.UIObject
          com.google.gwt.user.client.ui.Widget
              com.google.gwt.user.client.ui.FocusWidget
                  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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