203 lines
7.9 KiB
Racket
203 lines
7.9 KiB
Racket
#lang scribble/doc
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@(require "common.rkt" scribble/eval)
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@(define class-eval (make-base-eval))
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@(interaction-eval #:eval class-eval (require racket/class racket/draw))
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@defclass/title[brush% object% ()]{
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A brush is a drawing tool with a color and a style that is used for
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filling in areas, such as the interior of a rectangle or ellipse. In
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a monochrome destination, all non-white brushes are drawn as black.
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In addition to its color and style, a brush can have a @deftech{brush stipple} bitmap.
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Painting with a
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stipple brush is similar to calling @method[dc<%> draw-bitmap] with
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the stipple bitmap in the filled region.
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As an alternative to a color, style, and stipple, a brush can have a
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@deftech{gradient} that is a @racket[linear-gradient%] or
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@racket[radial-gradient%]. When a brush has a gradient and the target
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for drawing is not monochrome, then other brush settings are
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ignored. With a gradient, for each point in a drawing destination,
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the gradient associates a color to the point based on starting and
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ending colors and starting and ending lines (for a linear gradient)
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or circles (for a radial gradient); a gradient-assigned color is
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applied for each point that is touched when drawing with the brush.
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By default, coordinates in the gradient are transformed by the
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drawing context's transformation when the brush is used, but a brush
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can have its own @deftech{gradient transformation} that is used, instead.
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A gradient transformation has the same representation and meaning as for
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@xmethod[dc<%> get-transformation].
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A @deftech{brush style} is one of the following (but is ignored if the brush
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has a @tech{gradient} and the target is not monochrome):
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@itemize[
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@item{@indexed-racket['transparent] --- Draws with no effect (on the
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interior of the drawn shape).}
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@item{@indexed-racket['solid] --- Draws using the brush's color. If a
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monochrome @tech{brush stipple} is installed into the brush, black pixels
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from the stipple are transferred to the destination using the
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brush's color, and white pixels from the stipple are not
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transferred.}
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@item{@indexed-racket['opaque] --- The same as @racket['solid] for a color
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@tech{brush stipple}. For a monochrome stipple, white pixels from
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the stipple are
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transferred to the destination using the destination's
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background color.}
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@item{@indexed-racket['xor] --- The same as @racket['solid], accepted
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only for partial backward compatibility.}
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@item{@indexed-racket['hilite] --- Draws with black and a @racket[0.3] alpha.}
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@item{@indexed-racket['panel] --- The same as @racket['solid], accepted
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only for partial backward compatibility.}
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@item{The following modes correspond to built-in @tech{brush stipples} drawn in
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@racket['solid] mode:
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@itemize[
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@item{@indexed-racket['bdiagonal-hatch] --- diagonal lines, top-left to bottom-right}
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@item{@indexed-racket['crossdiag-hatch] --- crossed diagonal lines}
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@item{@indexed-racket['fdiagonal-hatch] --- diagonal lines, top-right to bottom-left}
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@item{@indexed-racket['cross-hatch] --- crossed horizontal and vertical lines}
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@item{@indexed-racket['horizontal-hatch] --- horizontal lines}
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@item{@indexed-racket['vertical-hatch] --- vertical lines}
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]
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However, when a specific @tech{brush stipple} is installed into the brush,
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the above modes are ignored and @racket['solid] is
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used, instead.}
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]
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@index['("drawing" "outlines")]{To} draw outline shapes (such as
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unfilled boxes and ellipses), use the @racket['transparent] brush
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style.
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To avoid creating multiple brushes with the same characteristics, use
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the global @racket[brush-list%] object
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@indexed-racket[the-brush-list], or provide a color and style to
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@xmethod[dc<%> set-brush].
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@defconstructor[([color (or/c string? (is-a?/c color%)) "black"]
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[style (one-of/c 'transparent 'solid 'opaque
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'xor 'hilite 'panel
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'bdiagonal-hatch 'crossdiag-hatch
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'fdiagonal-hatch 'cross-hatch
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'horizontal-hatch 'vertical-hatch)
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'solid]
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[stipple (or/c #f (is-a?/c bitmap%))
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#f]
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[gradient (or/c #f
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(is-a?/c linear-gradient%)
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(is-a?/c radial-gradient%))
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#f]
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[transformation (or/c #f (vector/c (vector/c real? real? real?
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real? real? real?)
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real? real? real? real? real?))])]{
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Creates a brush with the given color, @tech{brush style}, @tech{brush stipple}, @tech{gradient}, and
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@tech{gradient transformation}. For the case that the color is specified
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using a name, see @racket[color-database<%>] for information about
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color names; if the name is not known, the brush's color is black.}
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@defmethod[(get-color)
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(is-a?/c color%)]{
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Returns the brush's color.
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}
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@defmethod[(get-stipple)
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(or/c (is-a?/c bitmap%) #f)]{
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Gets the @tech{brush stipple} bitmap, or @racket[#f] if the brush has no stipple.}
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@defmethod[(get-gradient)
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(or/c (is-a?/c linear-gradient%)
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(is-a?/c radial-gradient%)
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#f)]{
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Gets the @tech{gradient}, or @racket[#f] if the brush has no gradient.}
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@defmethod[(get-style)
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(one-of/c 'transparent 'solid 'opaque
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'xor 'hilite 'panel
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'bdiagonal-hatch 'crossdiag-hatch
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'fdiagonal-hatch 'cross-hatch
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'horizontal-hatch 'vertical-hatch)]{
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Returns the @tech{brush style}. See @racket[brush%] for information about
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brush styles.}
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@defmethod[(get-transformation) (or/c #f (vector/c (vector/c real? real? real? real? real? real?)
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real? real? real? real? real?))]{
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Returns the brush's @tech{gradient transformation}, if any.
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If a brush with a gradient also has a transformation, then the
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transformation applies to the gradient's coordinates instead of the
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target drawing context's transformation; otherwise, the target drawing
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context's transformation applies to gradient coordinates.}
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@defmethod*[([(set-color [color (is-a?/c color%)])
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void?]
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[(set-color [color-name string?])
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void?]
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[(set-color [red (integer-in 0 255)]
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[green (integer-in 0 255)]
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[blue (integer-in 0 255)])
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void?])]{
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Sets the brush's color. A brush cannot be modified if it was obtained
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from a @racket[brush-list%] or while it is selected into a drawing
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context.
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For the case that the color is specified using a string, see
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@racket[color-database<%>] for information about color names.
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}
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@defmethod[(set-stipple [bitmap (or/c (is-a?/c bitmap%) #f)])
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void?]{
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Sets or removes the @tech{brush stipple} bitmap, where @racket[#f] removes the
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stipple. See @racket[brush%] for information about drawing with
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stipples.
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If @racket[bitmap] is modified while is associated with a brush, the
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effect on the brush is unspecified. A brush cannot be modified if it
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was obtained from a @racket[brush-list%] or while it is selected into
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a drawing context.
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}
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@defmethod[(set-style [style (one-of/c 'transparent 'solid 'opaque
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'xor 'hilite 'panel
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'bdiagonal-hatch 'crossdiag-hatch
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'fdiagonal-hatch 'cross-hatch
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'horizontal-hatch 'vertical-hatch)])
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void?]{
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Sets the @tech{brush style}. See
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@racket[brush%] for information about the possible styles.
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A brush cannot be modified if it was obtained from a
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@racket[brush-list%] or while it is selected into a drawing
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context.
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}}
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@(close-eval class-eval)
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