A pen is a drawing tool with a color, width, and style. A pen draws
lines and outlines, such as the outline of a rectangle. In a
monochrome destination, all non-white pens are drawn as black.
In addition to its color, width, and style, a pen can have a stipple
bitmap. Painting with a stipple pen is similar to
calling draw-bitmap with the stipple bitmap in region
painted by the pen.
A pen’s style is one of the following:
'transparent — Draws with no effect (on the
outline of the drawn shape).
'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.
'xor — The same as 'solid, accepted
only for partial backward compatibility.
'hilite — Draws with black and a 0.3 alpha.
The following special pen modes use the pen’s color, and they only
apply when a stipple is not used:
'dot
'long-dash
'short-dash
'dot-dash
'xor-dot
'xor-long-dash
'xor-short-dash
'xor-dot-dash
To avoid creating multiple pens with the same characteristics, use the
global pen-list% object the-pen-list, or
provide a color, width, and style to set-pen in dc<%>.
When drawing in 'smoothed or 'aligned mode, a pen’s
size is truncated after scaling to an integral size. A pen of size
0 (after truncation, if applicable) uses a non-zero,
scale-insensitive line size for the destination drawing context:
1/4 unit (after scaling) for post-script-dc% or
pdf-dc% contexts in 'smoothed mode, or 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 1.
| (new pen% | [ | [color color] | | | | | | | | [width width] | | | | | | | | [style style] | | | | | | | | [cap cap] | | | | | | | | [join join] | | | | | | | | [stipple stipple]]) | | → | | (is-a?/c pen%) |
|
| color : (or/c string? (is-a?/c color%)) = "black" |
| width : (real-in 0 255) = 0 |
| | style | | : | | | (one-of/c 'transparent 'solid 'xor 'hilite | | 'dot 'long-dash 'short-dash 'dot-dash | | 'xor-dot 'xor-long-dash 'xor-short-dash | | 'xor-dot-dash) |
| | | | | = | | 'solid |
|
| cap : (one-of/c 'round 'projecting 'butt) = 'round |
| join : (one-of/c 'round 'bevel 'miter) = 'round |
| stipple : (or/c #f (is-a?/c bitmap%)) = #f |
Creates a pen with the given color, width, style, cap style (see
get-cap), join style (see
get-join), and
stipple. For the case that the color is specified using a name, see
color-database<%> for information about color names; if the
name is not known, the pen’s color is black.
Returns the pen cap style, which determines the shape of a line at
each of its ending points when drawn by
draw-line or at the
non-connecting ends of lines when drawn by
draw-lines or
draw-path. The default is
'round, which draws the
end of a line as a semi-circle. The
'projecting style draws a
square in place of the semi-circle (i.e., past the point at which the
line stops). The
'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
('round, 'butt, and then 'projecting) and puts
a little red dot on the end points of the line.
Examples: |
| | > (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) |
| 
|
|
Returns the pen’s color object.
Returns the pen join style that is used between multiple lines
connected through
draw-lines,
draw-rectangle,
draw-polygon, or
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
'butt line endings. The default join style is
'round, which fills under an arc that lines up with the
outside of each of the two lines. The
'bevel style fills in
the gap without adding extra pixels (i.e., it makes a blunt
corner). The
'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).
This code shows the three join styles
('round, 'bevel and then '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: |
| > (define points '((100 . 100) | | (0 . 0) | | (0 . 100) | | (40 . 100))) |
| | | > (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) |
| 
|
|
Gets the current stipple bitmap, or returns #f if no stipple
bitmap is installed.
| (send a-pen get-style) |
| | → | | | (one-of/c 'transparent 'solid 'xor 'hilite | | 'dot 'long-dash 'short-dash 'dot-dash | | 'xor-dot 'xor-long-dash 'xor-short-dash | | 'xor-dot-dash) |
|
|
Returns the pen style. See
pen% for information about
possible styles.
Returns the pen width.
Sets the pen cap style. See
get-cap for information about cap
styles.
A pen cannot be modified if it was obtained from a pen-list%
or while it is selected into a drawing context.
Sets the pen color.
A pen cannot be modified if it was obtained from a
pen-list% or while it is selected into a drawing context.
Sets the pen join style. See
get-join for information about join
styles.
A pen cannot be modified if it was obtained from a
pen-list% or while it is selected into a drawing context.
Sets the pen stipple bitmap, where #f turns off the stipple bitmap.
If 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 pen-list% or while it is selected into a
drawing context.
| (send a-pen set-style style) → void? |
| | style | | : | | | (one-of/c 'transparent 'solid 'xor 'hilite | | 'dot 'long-dash 'short-dash 'dot-dash | | 'xor-dot 'xor-long-dash 'xor-short-dash | | 'xor-dot-dash) |
|
|
Sets the pen style. See
pen% for information about the
possible styles.
A pen cannot be modified if it was obtained from a
pen-list% or while it is selected into a drawing context.
Sets the pen width.
A pen cannot be modified if it was obtained from a
pen-list% or while it is selected into a drawing context.