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added some examples for pen cap and join styles

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This commit is contained in:
Robby Findler 2011-03-30 09:41:03 -05:00
parent e28a6832ca
commit d265231452
2 changed files with 108 additions and 30 deletions
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2
collects/scribblings/draw/common.rkt
View File

@ -1,12 +1,14 @@
(module common racket/base
(require scribble/manual
scribble/basic
scribble/eval
racket/class
racket/contract
"blurbs.ss"
(only-in "../reference/mz.ss" AllUnix exnraise))
(provide (all-from-out scribble/manual)
(all-from-out scribble/basic)
(all-from-out scribble/eval)
(all-from-out racket/class)
(all-from-out racket/contract)
(all-from-out "blurbs.ss")

136
collects/scribblings/draw/pen-class.scrbl
View File

@ -1,5 +1,11 @@
#lang scribble/doc
@(require "common.ss")
@(require "common.rkt"
(for-label slideshow/pict))
@(define pen-eval (make-base-eval))
@(interaction-eval
#:eval pen-eval
(require racket/draw slideshow/pict racket/class))
@defclass/title[pen% object% ()]{
@ -16,48 +22,48 @@ A pen's style is one of the following:
@itemize[
@item{@indexed-scheme['transparent] --- Draws with no effect (on the
@item{@indexed-racket['transparent] --- Draws with no effect (on the
outline of the drawn shape).}
@item{@indexed-scheme['solid] --- Draws using the pen's color. If a
@item{@indexed-racket['solid] --- Draws using the pen's color. If a
(monochrome) stipple is installed into the pen, black pixels
from the stipple are transferred to the destination using the
brush's color, and white pixels from the stipple are not
transferred.}
@item{@indexed-scheme['xor] --- The same as @racket['solid], accepted
@item{@indexed-racket['xor] --- The same as @racket['solid], accepted
only for partial backward compatibility.}
@item{@indexed-scheme['hilite] --- Draws with black and a @racket[0.3] alpha.}
@item{@indexed-racket['hilite] --- Draws with black and a @racket[0.3] alpha.}
@item{The following special pen modes use the pen's color, and they only
apply when a stipple is not used:
@itemize[
@item{@indexed-scheme['dot]}
@item{@indexed-scheme['long-dash]}
@item{@indexed-scheme['short-dash]}
@item{@indexed-scheme['dot-dash]}
@item{@indexed-scheme['xor-dot]}
@item{@indexed-scheme['xor-long-dash]}
@item{@indexed-scheme['xor-short-dash]}
@item{@indexed-scheme['xor-dot-dash]}
@item{@indexed-racket['dot]}
@item{@indexed-racket['long-dash]}
@item{@indexed-racket['short-dash]}
@item{@indexed-racket['dot-dash]}
@item{@indexed-racket['xor-dot]}
@item{@indexed-racket['xor-long-dash]}
@item{@indexed-racket['xor-short-dash]}
@item{@indexed-racket['xor-dot-dash]}
]}
]
To avoid creating multiple pens with the same characteristics, use the
global @scheme[pen-list%] object @indexed-scheme[the-pen-list], or
global @racket[pen-list%] object @indexed-racket[the-pen-list], or
provide a color, width, and style to @xmethod[dc<%> set-pen].
When drawing in @racket['smoothed] or @racket['aligned] mode, a pen's
size is truncated after scaling to an integral size. A pen of size
@scheme[0] (after truncation, if applicable) uses a non-zero,
@racket[0] (after truncation, if applicable) uses a non-zero,
scale-insensitive line size for the destination drawing context:
@racket[1/4] unit (after scaling) for @racket[post-script-dc%] or
@racket[pdf-dc%] contexts in @racket['smoothed] mode, or @racket[1]
unit (after scaling) for any other context. For example, in unscaled
canvas and bitmap contexts, a zero-width pen behaves the same as a
pen of size @scheme[1].
pen of size @racket[1].
@defconstructor[([color (or/c string? (is-a?/c color%)) "black"]
@ -77,7 +83,7 @@ When drawing in @racket['smoothed] or @racket['aligned] mode, a pen's
Creates a pen with the given color, width, style, cap style (see
@method[pen% get-cap]), join style (see @method[pen% get-join]), and
stipple. For the case that the color is specified using a name, see
@scheme[color-database<%>] for information about color names; if the
@racket[color-database<%>] for information about color names; if the
name is not known, the pen's color is black.
}
@ -88,12 +94,41 @@ Creates a pen with the given color, width, style, cap style (see
Returns the pen cap style, which determines the shape of a line at
each of its ending points when drawn by @method[dc<%> draw-line] or at the
non-connecting ends of lines when drawn by @method[dc<%> draw-lines] or
@method[dc<%> draw-path]. The default is @scheme['round], which draws the
@method[dc<%> draw-path]. The default is @racket['round], which draws the
end of a line as a semi-circle. The @racket['projecting] style draws a
square in place of the semi-circle (i.e., past the point at which the
line stops). The @racket['butt] style ends the line with a straight
edge, instead of projecting past the ending point of the line.
This code draws three diagonal lines, one with each of the possible caps
(@racket['round], @racket['butt], and then @racket['projecting]) and puts
a little red dot on the end points of the line.
@examples[#:eval
pen-eval
(define (plot-line dc x1 y1 x2 y2 cap)
(send dc set-pen
(send the-pen-list find-or-create-pen
"black" 40 'solid cap))
(send dc draw-line x1 y1 x2 y2)
(send dc set-brush "red" 'solid)
(send dc set-pen "black" 1 'transparent)
(send dc draw-ellipse (- x1 4) (- y1 4) 8 8)
(send dc draw-ellipse (- x2 4) (- y2 4) 8 8))
(dc
(λ (dc dx dy)
(define old-pen (send dc get-pen))
(define old-brush (send dc get-brush))
(plot-line dc 20 30 80 90 'round)
(plot-line dc 100 30 160 90 'butt)
(plot-line dc 180 30 240 90 'projecting)
(send dc set-pen old-pen)
(send dc set-brush old-brush))
270 120)]
}
@defmethod[(get-color)
@ -112,18 +147,58 @@ draw-rectangle], @method[dc<%> draw-polygon], or @method[dc<%>
draw-path]. The join style fills the space that would be left at the
outside corner of two lines if they were draw separately with
@racket['butt] line endings. The default join style is
@scheme['round], which fills under an arc that lines up with the
@racket['round], which fills under an arc that lines up with the
outside of each of the two lines. The @racket['bevel] style fills in
the gap without adding extra pixels (i.e., it makes a blunt
corner). The @racket['miter] style fills the gap by adding pixels that
would be covered by both lines if they were extended past the corner
(i.e., it makes a sharp corner).}
(i.e., it makes a sharp corner).
This code shows the three join styles
(@racket['round], @racket['bevel] and then @racket['miter])
by drawing a sequence
of lines, first with a sharp corner and then with a right-angle.
Each of the end points of the lines i with a red dot.
@examples[#:eval
pen-eval
(define points '((100 . 100)
(0 . 0)
(0 . 100)
(40 . 100)))
(define (connect-points dc dx dy join)
(send dc set-pen
(send the-pen-list find-or-create-pen
"black" 40 'solid 'round join))
(send dc draw-lines points dx dy)
(send dc set-brush "red" 'solid)
(send dc set-pen "black" 1 'transparent)
(for ([pt (in-list points)])
(send dc draw-ellipse
(+ dx (car pt) -4) (+ dy (cdr pt) -4)
8 8)))
(dc
(λ (dc dx dy)
(define old-pen (send dc get-pen))
(define old-brush (send dc get-brush))
(connect-points dc 20 50 'round)
(connect-points dc 180 50 'bevel)
(connect-points dc 340 50 'miter)
(send dc set-pen old-pen)
(send dc set-brush old-brush))
460 170)]
}
@defmethod[(get-stipple)
(or/c (is-a?/c bitmap%) #f)]{
Gets the current stipple bitmap, or returns @scheme[#f] if no stipple
Gets the current stipple bitmap, or returns @racket[#f] if no stipple
bitmap is installed.
}
@ -134,7 +209,7 @@ Gets the current stipple bitmap, or returns @scheme[#f] if no stipple
'xor-dot 'xor-long-dash 'xor-short-dash
'xor-dot-dash)]{
Returns the pen style. See @scheme[pen%] for information about
Returns the pen style. See @racket[pen%] for information about
possible styles.
}
@ -152,7 +227,7 @@ Returns the pen width.
Sets the pen cap style. See @method[pen% get-cap] for information about cap
styles.
A pen cannot be modified if it was obtained from a @scheme[pen-list%]
A pen cannot be modified if it was obtained from a @racket[pen-list%]
or while it is selected into a drawing context.
}
@ -169,7 +244,7 @@ A pen cannot be modified if it was obtained from a @scheme[pen-list%]
Sets the pen color.
A pen cannot be modified if it was obtained from a
@scheme[pen-list%] or while it is selected into a drawing context.
@racket[pen-list%] or while it is selected into a drawing context.
}
@ -180,18 +255,18 @@ Sets the pen join style. See @method[pen% get-join] for information about join
styles.
A pen cannot be modified if it was obtained from a
@scheme[pen-list%] or while it is selected into a drawing context.
@racket[pen-list%] or while it is selected into a drawing context.
}
@defmethod[(set-stipple [bitmap (or/c (is-a?/c bitmap%) #f)])
void?]{
Sets the pen stipple bitmap, where @scheme[#f] turns off the stipple bitmap.
Sets the pen stipple bitmap, where @racket[#f] turns off the stipple bitmap.
If @racket[bitmap] is modified while is associated with a pen, the
effect on the pen is unspecified. A pen cannot be modified if it was
obtained from a @scheme[pen-list%] or while it is selected into a
obtained from a @racket[pen-list%] or while it is selected into a
drawing context.
}
@ -202,11 +277,11 @@ If @racket[bitmap] is modified while is associated with a pen, the
'xor-dot-dash)])
void?]{
Sets the pen style. See @scheme[pen%] for information about the
Sets the pen style. See @racket[pen%] for information about the
possible styles.
A pen cannot be modified if it was obtained from a
@scheme[pen-list%] or while it is selected into a drawing context.
@racket[pen-list%] or while it is selected into a drawing context.
}
@ -216,7 +291,8 @@ A pen cannot be modified if it was obtained from a
Sets the pen width.
A pen cannot be modified if it was obtained from a
@scheme[pen-list%] or while it is selected into a drawing context.
@racket[pen-list%] or while it is selected into a drawing context.
}}
@close-eval[pen-eval]