org.eclipse.swt.widgets

Class Canvas

java.lang.Object

org.eclipse.swt.widgets.Widget

org.eclipse.swt.widgets.Control

org.eclipse.swt.widgets.Scrollable

org.eclipse.swt.widgets.Composite

org.eclipse.swt.widgets.Canvas

All Implemented Interfaces:

Drawable

Direct Known Subclasses:

AnimatedProgress, CLabel, Decorations, GLCanvas, StyledText, TableCursor, TreeCursor

public class Canvas
extends Composite

Instances of this class provide a surface for drawing arbitrary graphics.

Styles:

(none)

Events:

(none)

This class may be subclassed by custom control implementors who are building controls that are not constructed from aggregates of other controls. That is, they are either painted using SWT graphics calls or are handled by native methods.

See Also:

Composite, Canvas snippets, SWT Example: ControlExample, Sample code and further information

Structure Diagram

Field Summary

Fields

Modifier and Type	Field and Description
(package private) Caret	caret
(package private) IME	ime

Fields inherited from class org.eclipse.swt.widgets.Composite

backgroundMode, layout, layoutCount, lpwp, tabList

Fields inherited from class org.eclipse.swt.widgets.Scrollable

horizontalBar, verticalBar

Fields inherited from class org.eclipse.swt.widgets.Control

accessible, background, backgroundImage, cursor, drawCount, font, foreground, handle, layoutData, menu, parent, region, toolTipText

Fields inherited from class org.eclipse.swt.widgets.Widget

CANVAS, data, DEFAULT_HEIGHT, DEFAULT_WIDTH, DISABLED, display, DISPOSE_SENT, DISPOSED, DRAG_DETECT, DRAW_BACKGROUND, eventTable, FOREIGN_HANDLE, HIDDEN, IGNORE_WM_CHANGEUISTATE, KEYED_DATA, LAYOUT_CHANGED, LAYOUT_CHILD, LAYOUT_NEEDED, MAJOR, MINOR, MOVE_DEFERRED, MOVE_OCCURRED, PARENT_BACKGROUND, RELEASED, RESIZE_DEFERRED, RESIZE_OCCURRED, SKIN_NEEDED, state, style, THEME_BACKGROUND, TRACK_MOUSE

Constructor Summary

Constructors

Constructor and Description
Canvas() Prevents uninitialized instances from being created outside the package.
Canvas(Composite parent, int style) Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

Method Summary

Methods

Modifier and Type	Method and Description
(package private) void	clearArea(int x, int y, int width, int height)
void	drawBackground(GC gc, int x, int y, int width, int height) Fills the interior of the rectangle specified by the arguments, with the receiver's background.
Caret	getCaret() Returns the caret.
IME	getIME() Returns the IME.
(package private) void	releaseChildren(boolean destroy)
(package private) void	reskinChildren(int flags)
void	scroll(int destX, int destY, int x, int y, int width, int height, boolean all) Scrolls a rectangular area of the receiver by first copying the source area to the destination and then causing the area of the source which is not covered by the destination to be repainted.
void	setCaret(Caret caret) Sets the receiver's caret.
void	setFont(Font font) Sets the font that the receiver will use to paint textual information to the font specified by the argument, or to the default font for that kind of control if the argument is null.
void	setIME(IME ime) Sets the receiver's IME.
(package private) TCHAR	windowClass()
(package private) int	windowProc(int hwnd, int msg, int wParam, int lParam)
(package private) LRESULT	WM_CHAR(int wParam, int lParam)
(package private) LRESULT	WM_IME_COMPOSITION_START(int wParam, int lParam)
(package private) LRESULT	WM_IME_COMPOSITION(int wParam, int lParam)
(package private) LRESULT	WM_IME_ENDCOMPOSITION(int wParam, int lParam)
(package private) LRESULT	WM_INPUTLANGCHANGE(int wParam, int lParam)
(package private) LRESULT	WM_KILLFOCUS(int wParam, int lParam)
(package private) LRESULT	WM_LBUTTONDOWN(int wParam, int lParam)
(package private) LRESULT	WM_SETFOCUS(int wParam, int lParam)
(package private) LRESULT	WM_SIZE(int wParam, int lParam)
(package private) LRESULT	WM_WINDOWPOSCHANGED(int wParam, int lParam)
(package private) LRESULT	WM_WINDOWPOSCHANGING(int wParam, int lParam)

Methods inherited from class org.eclipse.swt.widgets.Composite

_getChildren, _getTabList, changed, checkBuffered, checkComposited, checkSubclass, computeSize, computeTabList, copyArea, createHandle, drawBackground, findDeferredControl, findMenus, fixChildren, fixTabList, getBackgroundMode, getChildren, getChildrenCount, getLayout, getLayoutDeferred, getTabList, hooksKeys, isLayoutDeferred, layout, layout, layout, layout, layout, markLayout, minimumSize, redrawChildren, releaseParent, releaseWidget, removeControl, resizeChildren, resizeChildren, resizeEmbeddedHandle, sendResize, setBackgroundMode, setBounds, setFocus, setLayout, setLayoutDeferred, setResizeChildren, setTabGroupFocus, setTabList, toolTipText, translateMnemonic, translateTraversal, updateBackgroundColor, updateBackgroundImage, updateBackgroundMode, updateFont, updateLayout, updateLayout, updateOrientation, updateUIState, widgetStyle, WM_ERASEBKGND, WM_GETDLGCODE, WM_GETFONT, WM_NCHITTEST, WM_PAINT, WM_PARENTNOTIFY, WM_PRINTCLIENT, WM_SETFONT, WM_SYSCOLORCHANGE, WM_SYSCOMMAND, WM_UPDATEUISTATE, wmNCPaint, wmNotify

Methods inherited from class org.eclipse.swt.widgets.Scrollable

callWindowProc, computeTrim, createScrollBar, createWidget, destroyScrollBar, getClientArea, getHorizontalBar, getScrollbarsMode, getVerticalBar, scrolledHandle, widgetExtStyle, windowProc, WM_HSCROLL, WM_MOUSEWHEEL, WM_VSCROLL, wmScroll, wmScrollWheel

Methods inherited from class org.eclipse.swt.widgets.Control

addControlListener, addDragDetectListener, addFocusListener, addGestureListener, addHelpListener, addKeyListener, addMenuDetectListener, addMouseListener, addMouseMoveListener, addMouseTrackListener, addMouseWheelListener, addPaintListener, addTouchListener, addTraverseListener, binarySearch, borderHandle, checkBackground, checkBorder, checkGesture, checkHandle, checkMirrored, computeSize, computeTabGroup, computeTabRoot, defaultBackground, defaultFont, defaultForeground, deregister, destroyWidget, dragDetect, dragDetect, dragDetect, drawBackground, drawBackground, drawBackground, drawImageBackground, drawThemeBackground, enableDrag, enableWidget, fillBackground, fillImageBackground, fillThemeBackground, findBackgroundControl, findBrush, findCursor, findImageControl, findMnemonic, findThemeControl, fixFocus, forceFocus, forceResize, getAccessible, getBackground, getBackgroundImage, getBackgroundPixel, getBorderWidth, getBounds, getClipboardText, getCodePage, getCursor, getDragDetect, getDrawing, getEnabled, getFont, getForeground, getForegroundPixel, getLayoutData, getLocation, getMenu, getMonitor, getOrientation, getParent, getPath, getRegion, getShell, getSize, getToolTipText, getTouchEnabled, getVisible, hasCursor, hasFocus, internal_dispose_GC, internal_new_GC, isActive, isEnabled, isFocusAncestor, isFocusControl, isReparentable, isShowing, isTabGroup, isTabItem, isVisible, mapEvent, menuShell, mnemonicHit, mnemonicMatch, moveAbove, moveBelow, new_Accessible, new_GC, pack, pack, print, printWidget, redraw, redraw, redraw, register, releaseHandle, removeControlListener, removeDragDetectListener, removeFocusListener, removeGestureListener, removeHelpListener, removeKeyListener, removeMenuDetectListener, removeMouseListener, removeMouseMoveListener, removeMouseTrackListener, removeMouseWheelListener, removePaintListener, removeTouchListener, removeTraverseListener, sendFocusEvent, sendGestureEvent, sendMove, sendTouchEvent, setBackground, setBackground, setBackgroundImage, setBackgroundImage, setBackgroundPixel, setBounds, setBounds, setBounds, setCapture, setCursor, setCursor, setDefaultFont, setDragDetect, setEnabled, setForeground, setForegroundPixel, setLayoutData, setLocation, setLocation, setMenu, setOrientation, setParent, setRadioFocus, setRadioSelection, setRedraw, setRegion, setSavedFocus, setSize, setSize, setTabItemFocus, setToolTipText, setToolTipText, setTouchEnabled, setVisible, showWidget, sort, subclass, toControl, toControl, toDisplay, toDisplay, topHandle, translateAccelerator, translateMnemonic, traverse, traverse, traverse, traverse, traverse, traverseEscape, traverseGroup, traverseItem, traverseMnemonic, traversePage, traverseReturn, unsubclass, update, update, updateImages, widgetCreateStruct, widgetParent, WM_ACTIVATE, WM_CAPTURECHANGED, WM_CHANGEUISTATE, WM_CLEAR, WM_CLOSE, WM_COMMAND, WM_CONTEXTMENU, WM_CTLCOLOR, WM_CUT, WM_DESTROY, WM_DRAWITEM, WM_ENDSESSION, WM_ENTERIDLE, WM_GESTURE, WM_GETMINMAXINFO, WM_GETOBJECT, WM_HELP, WM_HOTKEY, WM_IME_CHAR, WM_INITMENUPOPUP, WM_KEYDOWN, WM_KEYUP, WM_LBUTTONDBLCLK, WM_LBUTTONUP, WM_MBUTTONDBLCLK, WM_MBUTTONDOWN, WM_MBUTTONUP, WM_MEASUREITEM, WM_MENUCHAR, WM_MENUSELECT, WM_MOUSEACTIVATE, WM_MOUSEHOVER, WM_MOUSEHWHEEL, WM_MOUSELEAVE, WM_MOUSEMOVE, WM_MOVE, WM_NCACTIVATE, WM_NCCALCSIZE, WM_NCLBUTTONDOWN, WM_NCPAINT, WM_NOTIFY, WM_PALETTECHANGED, WM_PASTE, WM_PRINT, WM_QUERYENDSESSION, WM_QUERYNEWPALETTE, WM_QUERYOPEN, WM_RBUTTONDBLCLK, WM_RBUTTONDOWN, WM_RBUTTONUP, WM_SETCURSOR, WM_SETREDRAW, WM_SETTINGCHANGE, WM_SHOWWINDOW, WM_SYSCHAR, WM_SYSKEYDOWN, WM_SYSKEYUP, WM_TABLET_FLICK, WM_TIMER, WM_TOUCH, WM_UNDO, WM_UNINITMENUPOPUP, WM_XBUTTONDBLCLK, WM_XBUTTONDOWN, WM_XBUTTONUP, wmColorChild, wmCommandChild, wmDrawChild, wmMeasureChild, wmNotifyChild, wmScrollChild

Methods inherited from class org.eclipse.swt.widgets.Widget

_addListener, addDisposeListener, addListener, checkBits, checkOpened, checkOrientation, checkParent, checkWidget, DeferWindowPos, dispose, dragDetect, error, filters, findItem, fixMnemonic, fixMnemonic, getData, getData, getDisplay, getListeners, getName, getNameText, getStyle, hooks, isDisposed, isListening, isValidSubclass, isValidThread, notifyListeners, postEvent, postEvent, release, removeDisposeListener, removeListener, removeListener, reskin, reskinWidget, sendDragEvent, sendDragEvent, sendEvent, sendEvent, sendEvent, sendEvent, sendKeyEvent, sendKeyEvent, sendMouseEvent, sendMouseEvent, sendMouseWheelEvent, sendSelectionEvent, sendSelectionEvent, setData, setData, setInputState, setKeyState, setLocationMask, SetWindowPos, showMenu, showMenu, toString, updateMenuLocation, wmCaptureChanged, wmChar, wmContextMenu, wmIMEChar, wmKeyDown, wmKeyUp, wmKillFocus, wmLButtonDblClk, wmLButtonDown, wmLButtonUp, wmMButtonDblClk, wmMButtonDown, wmMButtonUp, wmMouseHover, wmMouseHWheel, wmMouseLeave, wmMouseMove, wmMouseWheel, wmPaint, wmPrint, wmRButtonDblClk, wmRButtonDown, wmRButtonUp, wmSetFocus, wmSysChar, wmSysKeyDown, wmSysKeyUp, wmXButtonDblClk, wmXButtonDown, wmXButtonUp

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

caret

Caret caret

ime

IME ime

Constructor Detail

Canvas

Canvas()

Prevents uninitialized instances from being created outside the package.

Canvas

public Canvas(Composite parent,
      int style)

Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

The style value is either one of the style constants defined in class SWT which is applicable to instances of this class, or must be built by bitwise OR'ing together (that is, using the int "|" operator) two or more of those SWT style constants. The class description lists the style constants that are applicable to the class. Style bits are also inherited from superclasses.

Parameters:

parent - a composite control which will be the parent of the new instance (cannot be null)

style - the style of control to construct

Throws:

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the parent is null

SWTException -

• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent

See Also:

SWT, Widget.checkSubclass(), Widget.getStyle()

Method Detail

clearArea

void clearArea(int x,
             int y,
             int width,
             int height)

drawBackground

public void drawBackground(GC gc,
                  int x,
                  int y,
                  int width,
                  int height)

Fills the interior of the rectangle specified by the arguments, with the receiver's background.

Parameters:

gc - the gc where the rectangle is to be filled

x - the x coordinate of the rectangle to be filled

y - the y coordinate of the rectangle to be filled

width - the width of the rectangle to be filled

height - the height of the rectangle to be filled

Throws:

java.lang.IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the gc is null
• ERROR_INVALID_ARGUMENT - if the gc has been disposed

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

Since:

3.2

getCaret

public Caret getCaret()

Returns the caret.

The caret for the control is automatically hidden and shown when the control is painted or resized, when focus is gained or lost and when an the control is scrolled. To avoid drawing on top of the caret, the programmer must hide and show the caret when drawing in the window any other time.

Returns:

the caret for the receiver, may be null

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getIME

public IME getIME()

Returns the IME.

Returns:

the IME

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

Since:

3.4

releaseChildren

void releaseChildren(boolean destroy)

Overrides:

releaseChildren in class Composite

reskinChildren

void reskinChildren(int flags)

Overrides:

reskinChildren in class Composite

scroll

public void scroll(int destX,
          int destY,
          int x,
          int y,
          int width,
          int height,
          boolean all)

Scrolls a rectangular area of the receiver by first copying the source area to the destination and then causing the area of the source which is not covered by the destination to be repainted. Children that intersect the rectangle are optionally moved during the operation. In addition, all outstanding paint events are flushed before the source area is copied to ensure that the contents of the canvas are drawn correctly.

Parameters:

destX - the x coordinate of the destination

destY - the y coordinate of the destination

x - the x coordinate of the source

y - the y coordinate of the source

width - the width of the area

height - the height of the area

all - trueif children should be scrolled, and false otherwise

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setCaret

public void setCaret(Caret caret)

Sets the receiver's caret.

The caret for the control is automatically hidden and shown when the control is painted or resized, when focus is gained or lost and when an the control is scrolled. To avoid drawing on top of the caret, the programmer must hide and show the caret when drawing in the window any other time.

Parameters:

caret - the new caret for the receiver, may be null

Throws:

java.lang.IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the caret has been disposed

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setFont

public void setFont(Font font)

Description copied from class: Control

Sets the font that the receiver will use to paint textual information to the font specified by the argument, or to the default font for that kind of control if the argument is null.

Overrides:

setFont in class Control

Parameters:

font - the new font (or null)

setIME

public void setIME(IME ime)

Sets the receiver's IME.

Parameters:

ime - the new IME for the receiver, may be null

Throws:

java.lang.IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the IME has been disposed

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

Since:

3.4

windowClass

TCHAR windowClass()

Overrides:

windowClass in class Scrollable

windowProc

int windowProc(int hwnd,
             int msg,
             int wParam,
             int lParam)

Overrides:

windowProc in class Control

WM_CHAR

LRESULT WM_CHAR(int wParam,
              int lParam)

Overrides:

WM_CHAR in class Control

WM_IME_COMPOSITION

LRESULT WM_IME_COMPOSITION(int wParam,
                         int lParam)

Overrides:

WM_IME_COMPOSITION in class Control

WM_IME_COMPOSITION_START

LRESULT WM_IME_COMPOSITION_START(int wParam,
                               int lParam)

Overrides:

WM_IME_COMPOSITION_START in class Control

WM_IME_ENDCOMPOSITION

LRESULT WM_IME_ENDCOMPOSITION(int wParam,
                            int lParam)

Overrides:

WM_IME_ENDCOMPOSITION in class Control

WM_INPUTLANGCHANGE

LRESULT WM_INPUTLANGCHANGE(int wParam,
                         int lParam)

Overrides:

WM_INPUTLANGCHANGE in class Control

WM_KILLFOCUS

LRESULT WM_KILLFOCUS(int wParam,
                   int lParam)

Overrides:

WM_KILLFOCUS in class Control

WM_LBUTTONDOWN

LRESULT WM_LBUTTONDOWN(int wParam,
                     int lParam)

Overrides:

WM_LBUTTONDOWN in class Composite

WM_SETFOCUS

LRESULT WM_SETFOCUS(int wParam,
                  int lParam)

Overrides:

WM_SETFOCUS in class Control

WM_SIZE

LRESULT WM_SIZE(int wParam,
              int lParam)

Overrides:

WM_SIZE in class Composite

WM_WINDOWPOSCHANGED

LRESULT WM_WINDOWPOSCHANGED(int wParam,
                          int lParam)

Overrides:

WM_WINDOWPOSCHANGED in class Control

WM_WINDOWPOSCHANGING

LRESULT WM_WINDOWPOSCHANGING(int wParam,
                           int lParam)

Overrides:

WM_WINDOWPOSCHANGING in class Control