superclass: object% |
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. On a monochrome display, all non-white pens are drawn as black.
In addition to its color, width, and style, a pen can have a stipple bitmap that is a 8 x 8 monochrome bitmap. This stipple is used only in unsmoothed mode (see set-smoothing) or in a PostScript drawing context. 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 – In unsmoothed mode, the pen’s color or colored stipple is xor-ed 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.
In a smoothing mode, 'xor is equivalent to 'solid.
'hilite – In unsmoothed mode, existing destination pixels are “highlighted” in a platform-specific way when the pen color is black. Under Windows for a color drawing context, the inverted RGB components of destination pixel are combined with the RGB components of the system-wide highlight color using a bitwise “or”, and the combination is used. Under Mac OS X for a color drawing context, the inverted RGB components of the system-wide highlight color are subtracted from the RGB components of each destination pixel, and the difference (or 0 for a negative result) is used. Under X or for any monochrome drawing context, 'hilite is the same as 'xor. In a smoothing mode, 'hilite is treated like 'solid.
The following special pen modes use the pen’s color, and they only apply when a stipple is not used:
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<%>.
A pen of size 0 uses the minimum line size for the destination drawing context. In (unscaled) canvases and bitmaps in unsmoothed mode, a zero-width pen behaves the nearly same as a pen of size 1. In a smoothing mode (including all post-script-dc% drawing), a pen of size 0 draws a line thinner than a pen of size 1. If the pen’s width is not an integer, then the width is truncated to an integer (even before scaling) in unsmoothed mode.
(make-object pen%) → (is-a?/c pen%) | ||||||||||
(make-object pen% color width style) → (is-a?/c pen%) | ||||||||||
width : (real-in 0 255) | ||||||||||
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(make-object pen% color-name width style) → (is-a?/c pen%) | ||||||||||
color-name : string? | ||||||||||
width : (real-in 0 255) | ||||||||||
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When no argument are provided, the result is a solid black pen of width 0. Otherwise, the result is a pen with the given color, width, and style. 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 (Windows unsmoothed, X unsmoothed, all smoothing). The default is 'round.
Returns the pen’s color object.
Returns the pen join style (Windows unsmoothed, X unsmoothed, all smoothing). The default is 'round.
Gets the current stipple bitmap, or returns #f if no stipple bitmap is installed.
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Returns the pen style. See pen% for information about possible styles.
Returns the pen width.
cap-style : (one-of/c 'round 'projecting 'butt) |
Sets the pen cap style (Windows unsmoothed, X unsmoothed, all smoothing). 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.
color-name : string? |
red : (integer-in 0 255) |
green : (integer-in 0 255) |
blue : (integer-in 0 255) |
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.
join-style : (one-of/c 'round 'bevel 'miter) |
Sets the pen join style (Windows unsmoothed, X unsmoothed, all smoothing). 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.
(send a-pen set-stipple stipple) → void? |
Sets the pen stipple bitmap, which must be an 8 x 8 monochrome bitmap or #f, which turns off the stipple bitmap.
A bitmap cannot be used as a stipple if it is selected into a bitmap-dc% object; if the given bitmap is selected into a bitmap-dc% object, an exn:fail:contract exception is raised. A pen cannot be modified if it was obtained from a pen-list% or while it is selected into a drawing context.
A pen’s stipple is not used in a smoothing mode, except for a post-script-dc% (which is always in smoothed mode).
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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.
width : (real-in 0 255) |
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.