Class Canvas

All Implemented Interfaces:
Drawable
Direct Known Subclasses:
AbstractHyperlink, AnimatedProgress, CLabel, Decorations, ExpandableComposite, FormText, GLCanvas, HyperlinkLabel, ImageBasedFrame, 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:
  • Constructor Details

    • 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:
      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:
  • Method Details

    • 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:
      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
    • 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:
      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:
      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