6.4  brush%

A brush is a drawing tool with a color and a style that is used for filling in areas, such as the interior of a rectangle or ellipse. On a monochrome display, all non-white brushes are drawn as black.

In addition to its color and style, a brush can have a stipple bitmap. Painting with a stipple brush is similar to calling draw-bitmap with the stipple bitmap in the filled region, except that the bitmap may not be scaled in the same way (depending on the platform and device).

A brush's style is one of the following:

• 'transparent -- Draws with no effect (on the interior of the drawn shape).

• 'solid -- Draws using the brush's color. If a monochrome stipple is installed into the brush, black pixels from the stipple are transferred to the destination using the brush's color, and white pixels from the stipple are not transferred.

• 'opaque -- Same as 'solid, except when a monochrome stipple is installed; in that case, white pixels from the stipple are transferred to the destination using the destination's background color.

• 'xor -- If a color stipple is installed, 'xor is treated as 'solid. Otherwise, the brush's color or colored (monochrome) stipple is xored with existing destination pixel values. The 'xor mapping is unspecified for arbitrary color combinations, but the mapping provides two guarantees:

  • Black-and-white drawing to a color or monochrome destination always works as expected: black xor white = black, white xor black = black, black xor black = white, and white xor white = white.

  • Performing the same drawing operation twice in a row with 'xor is equivalent to a no-op.

• 'panel -- Draws with the same color and pattern as a panel background if the brush's color is the same as the color returned by get-panel-background and if the brush has no stipple.

• The following modes correspond to built-in stipples drawn in 'solid mode:

  • 'bdiagonal-hatch -- diagonal lines, top-left to bottom-right

  • 'crossdiag-hatch -- crossed diagonal lines

  • 'fdiagonal-hatch -- diagonal lines, top-right to bottom-left

  • 'cross-hatch -- crossed horizontal and vertical lines

  • 'horizontal-hatch -- horizontal lines

  • 'vertical-hatch -- vertical lines

  However, when a specific stipple is installed into the brush, the above modes are ignored and 'solid is used, instead.

To draw outline shapes (such as unfilled boxes and ellipses), use the 'transparent brush style. See set-style for more information about styles.

To avoid creating multiple brushes with the same characteristics, use the global brush-list% object the-brush-list.

• (make-object brush%) -> brush% object

  Creates a solid black brush.

  
  

• (make-object brush% color style) -> brush% object
     color : color% object
     style : symbol in '(transparent solid opaque xor panel bdiagonal-hatch crossdiag-hatch fdiagonal-hatch cross-hatch horizontal-hatch vertical-hatch)

  Creates a brush with the given color and style.

  
  

• (make-object brush% color-name style) -> brush% object
     color-name : string
     style : symbol in '(transparent solid opaque xor panel bdiagonal-hatch crossdiag-hatch fdiagonal-hatch cross-hatch horizontal-hatch vertical-hatch)

  Creates a brush with the given color and style, where the color is specified using a name; see color-database<%> for information about color names. If the name is not known, the brush's color is set to black.

  
  

Methods
    get-color
    get-stipple
    get-style
    set-color
    set-stipple
    set-style