ART(1) ART(1)
NAME
art, art2pic - edit line-art
SYNOPSIS
art [ font ]
art2pic file
DESCRIPTION
Art is an interactive program to create precise line-art in
the style of pic(1). It is mostly mouse-operated, with a few
commands entered from the keyboard. It divides its layer
into four areas: a menu bar at the top, a one-line rectangle
immediately below for echoing typed-in characters, another
one-line rectangle below that for printing messages, and a
large area at the bottom for displaying the drawing.
A small caret whose apex is the current point, appears on
the screen. The lines, arcs and other elements of a drawing
are constructed by placing the caret at each of a sequence
of points that define the item. When the caret moves, two
other markers (a square and a cross) trail it, showing its
previous positions. Items on the screen near the caret
attract it. Important points on items, like endpoints or
intersections, pull harder than more mundane points, making
precise alignment easy.
On request, art will automatically construct alignment lines
and circles, which it displays more faintly than items in
the drawing. Certain lines and points in a drawing are hot.
Art constructs circles of given radii and lines of given
slopes at hot points, and parallels at given distances from
hot lines and lines at given angles to their endpoints.
Menus pulled down from the menu bar control what alignment
items are constructed. Items are automatically heated when
added to the drawing and will be heated or cooled on com-
mand.
The `important points' on a line segment to which the caret
preferentially gravitates are its endpoints and midpoint.
On a circle, the center is important. On an arc, the end-
points are important. On a box, the corners, the midpoints
of the sides and the center are important. Likewise, on a
piece of text, the corners, midpoints and center of its
bounding box are important. On a spline, the control points
are important, and in a group, the important points of the
group members are important.
Whenever button 1 is pressed, the caret follows the mouse
cursor. On release, the item the caret is touching, if any,
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is selected and highlighted. If more than one item touches
the caret, clicking button 1 repeatedly will cycle through
them.
Pressing button 2 pops up a menu of commands that add new
items to the drawing. Every item is described by several
control points: a line by its endpoints, a circular arc by
its endpoints and a third point on the arc, and so forth. A
new item is specified by moving the caret in turn to each
control point but the last, selecting a menu entry with but-
ton two, then using button 1 to place the caret on the last
control point. (Buttons 2 and 3 will cancel the command.)
While the caret is being dragged to the last control point,
art displays and updates the item on the screen (``rubber-
banding''). In all cases, after making an addition to the
drawing, the new item becomes the current selection. The
button 2 menu operations are
line Add a line segment to the drawing. The two con-
trol points are the segment's endpoints.
circle Add a circle to the drawing. The first control
point is the center. The second is a point on
the circumference.
arc Add a circular arc to the drawing. The endpoints
are the first and third control points. The sec-
ond control point is an interior point of the
arc.
box Add a rectangle to the drawing. The box's sides
are vertical and horizontal. The two control
points are two diagonally opposite corners.
spline Add a spline curve to the drawing, or extend an
existing spline. Splines are a little more com-
plicated than other items because they may have
any number of control points. If the current
selection is not a spline, there are two control
points - the ends of a new spline. When a spline
is selected, the spline button adds a new control
point to the end of the spline closest to the
selected point.
group Add a group to the drawing. The two control
points are the diagonally opposite corners of a
rectangle. Any item partially or completely con-
tained in the rectangle is made part of the
group. Henceforth the group acts as a monolithic
item and may be moved, deleted or copied as a
unit. The open, close and flatten commands (on
button 3) allow manipulation of the items within
a group. Groups may be nested within other
groups.
Button 3's menu has commands to manipulate the current
selection.
delete Remove the selection from the drawing. If the
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whole drawing is selected, art asks for confirma-
tion by pressing mouse button 3. Buttons 1 and 2
cancel the command.
heat Heat the selected item.
copy Create a duplicate of the selected item. The
duplicate must be dragged to its intended posi-
tion using button 1. Buttons 2 and 3 cancel the
command.
edit Change the indicated point of the selected item.
Button 1 adjusts the point. Buttons 2 and 3 can-
cel the command. This command's behavior depends
on the kind of item and the point at which it is
selected.
If a line is selected near an endpoint, that end-
point moves and the other remains fixed. Both
endpoints of a line selected near its midpoint
move-its length and slope do not change.
If a circle selected at its center, it translates
without changing its radius. If selected on its
circumference, its radius changes but its center
remains fixed.
The control point of an arc or spline nearest the
selection point is modified.
If a box is selected near a corner, that corner
moves and the other remains fixed. If selected
near the middle of an edge, the edge moves, but
the opposite edge remains fixed. If selected
near its center, the whole box moves without
changing its size or shape.
A group or a piece of text translates, regardless
of the selection point.
open The selection must be a group. All commands now
operate on the members of the group.
close The most-recently opened group is closed. Any
changes made while it was open are propagated to
other copies.
flatten The selection must be a group. The items in the
group are inserted in its place in the drawing.
This undoes the effect of the group command.
Other copies of the group are unaffected.
Keyboard commands:
t text Add text to the drawing. The text is in the cur-
rent font and is drawn centered on the caret.
f name Set the current typeface. Name is the name of a
font file. Subdirectories of /lib/font/bit con-
tain many appropriate fonts.
D Redraw the display.
q Quit. Art exits, without asking for confirma-
tion.
w [file] Write the drawing into a file in art format.
File defaults to the last file mentioned in a
read or write command. Art files may be
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converted to pic(1) format by the art2pic com-
mand.
r [file] Read a drawing from a file. File defaults to the
last file mentioned in a read or write command.
c Cool everything. Every hot item is cooled.
a Select all items. The entire drawing is
selected.
d Drop anchor. The anchor is the fixed point for
the not-yet-implemented rotate and scale com-
mands.
Menus pulled down from the menu bar contain commands that
alter how art responds to user interaction.
slopes Most of the entries in this menu are numbers,
representing angles in degrees. Those that are
marked with a star are the inclination from hori-
zontal of alignment lines constructed at each hot
point of the drawing. Selecting a number toggles
the star on and off. The measure button measures
the slope of the line connecting the most recent
two points selected with the caret. The measure-
ment is printed, and a corresponding new entry is
made in the menu.
angles This menu behaves much like the slopes menu.
Items marked with a star are angles at which
alignment lines are drawn through the endpoints
of hot lines. The measure button measures the
angle indicated by the most recent three points
selected with the caret.
parallels Items marked with a star are distances at which
alignment lines are drawn parallel to hot lines.
The measure button measures the distance between
the most recent two points selected with the
caret. Distances are nominally in inches, but
the program believes the display pitch to be 100
pixels per inch.
circles Items marked with a star are radii of alignment
circles drawn with centers at hot points. The
measure button measures the distance between the
most recent two points selected with the caret.
grid Items in this menu activate a rectangular grid of
gravitating points. They have labels like
0,0+.1,.1. The first pair of numbers is the
coordinate of a point on the grid; the other pair
is the x and y displacements of other points.
The off item disables the grid (the default situ-
ation). Measure creates a custom-measured grid
using the last two positions of the caret as
diagonally adjacent grid-points.
gravity The starred entry on this menu is the maximum
distance that the caret will move from the mouse
cursor to snap to an item on the screen.
heating The heat new button toggles whether objects are
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automatically heated when created or modified.
The item is marked with a `*' if set, as it is
initially.
SEE ALSO
tweak(1)
BUGS
Only works on 2-bit displays (gnot, nextstation.) Doesn't
compute intersections of splines with circles or arcs. No
filled regions, line styles or arrowheads. Doesn't save
construction lines in files. Because it draws in xor mode
when rubber-banding, lines can momentarily disappear.
Tracks slowly in large drawings.
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