cadcraft/docs/plot-styles.md

Plot styles

A plot style table decides how objects print. CADCraft applies it to PDF plots (PLOT, EXPORTPDF and anything that plots through them). It also applies it to a layout shown with Display plot styles on: on screen and in the layout's PNG and SVG exports.

Tables

Kind	Picks the style by	Styles
Colour-dependent (.ctb)	the object's index colour (a true colour uses its nearest index colour)	exactly 255, Color_1 … Color_255
Named (.stb)	the object's PlotStyle property	Normal first, then any names

A style can set these:

Field	Meaning	"Use object" value
color	output colour, "#rrggbb"	absent / null
grayscale	print the colour as the grey of its luminance (Rec. 709 weights)	false
screening	ink intensity 0–100 %, mixing toward the white paper	100
linetype	linetype name (loaded, or from the built-in library; Continuous draws solid)	absent / null
lineweight	hundredths of a millimetre, 0–211; used when lineweights are plotted	absent / null
end, join, fill	line end, line join and area fill style	object

Colour 7 prints black.

Line ends, joins and fill patterns

• end and join shape lines wider than 0.25 mm on paper (from lineweights). The line is drawn as its filled outline: butt ends at the end point, square reaches half the width past it, round adds a half circle and diamond a point. miter joins meet in a point (bevelled past 10 half widths), bevel cuts the corner, round rounds it and diamond points out one half width. object is round, as lines are drawn anyway.
• fill replaces the solid fill of filled areas: 2D solids, traces, wide polylines, solid hatches and filled text. solid and object keep it solid. The patterns are CADCraft's own definitions, measured on paper and anchored to the sheet's origin. They repeat every 1 mm:

Fill	Pattern
checkerboard	0.5 mm squares, every other one filled
crosshatch	horizontal and vertical bars, 0.2 mm wide
diamonds	0.35 mm squares turned 45°, every 0.7 mm
horizontalBars, verticalBars	bars a third of the repeat wide
slantLeft, slantRight	\ and / bars a third of the repeat wide
squareDots	0.2 mm squares every 0.5 mm

Wipeouts are never patterned. A plot that would need more than two million pattern cells keeps the remaining areas solid. Layouts draw these while the display list is built. A model-space plot draws them at its plot scale.

Built-in tables

These are CADCraft's own definitions, not copies of any vendor's files.

Table	What it does
default.ctb	keeps every object property
monochrome.ctb	prints every colour black
grayscale.ctb	prints every colour as the grey of its luminance
default.stb	Normal (object properties), Black, Screened 50%, Thick (0.50 mm)
monochrome.stb	Normal prints black; Screened 50% prints black at 50 %

A table kept in the drawing shadows a built-in table of the same name.

Named plot styles

Layers have a plot style name (default Normal). Objects have ByLayer (the default), ByBlock or a style name. ByLayer takes the layer's style. On layer 0 inside a block, that is the block reference's layer. ByBlock takes the block reference's style. A name the table doesn't have prints as Normal. A colour-dependent table ignores the property.

Commands

• pagesetup {layout, plotStyleTable, displayPlotStyles} sets the layout's table and the Display plot styles flag. Without a layout, it reports the built-in tables in plotStyleTables.
• plot / exportpdf {plotStyleTable} replaces the page setup's table for one plot. "None" plots object colours.
• plotstyle {name, handles?} sets the objects' plot style. With nothing selected, it sets the current plot style for new objects (CPLOTSTYLE). Without name, it reports the current style and the named styles.
• layer.set {name, plotStyle} sets a layer's plot style.
• stylesmanager {action, …} manages the tables: list, get, new (kind, from), set (style: {name, …fields}, removeStyle, description), delete, load (path or text) and save (path, or returns text). Typed or chosen from File ▸ Plot Styles..., it opens the Plot Style Manager dialog.

Table files

Tables are saved in our own format: UTF-8 JSON with a format marker. Fields left at "use the object's" are omitted.

{
  "cadcraftPlotStyleTable": 1,
  "name": "office.stb",
  "description": "Office pens",
  "kind": "named",
  "styles": [
    { "name": "Normal" },
    { "name": "Pen 5", "color": "#000000", "screening": 40, "lineweight": 35, "linetype": "HIDDEN", "end": "round" }
  ]
}

• kind is colorDependent or named.
• end is one of object, butt, square, round or diamond.
• join is one of object, miter, bevel, round or diamond.
• fill is one of object, solid, checkerboard, crosshatch, diamonds, horizontalBars, slantLeft, slantRight, squareDots or verticalBars.
• color may also be written [r, g, b].

Reading fixes hostile values:

• Screening is capped at 100 and lineweights at 211.
• A colour-dependent table always gets 255 styles named Color_n.
• A named table gets unique style names (at most 1024), with Normal first.
• Files over 4 MB are refused.

Binary .ctb/.stb files are not read. We haven't found a public specification of that format.

In DXF files

• The page setup's table is PLOTSETTINGS group 7, and Display plot styles is plot layout flag 2 (group 70).
• Plot style names follow the DXF Reference. The named object dictionary entry ACAD_PLOTSTYLENAME is an ACDBDICTIONARYWDFLT whose entries name ACDBPLACEHOLDER objects (default Normal). Layers and objects point at them with group 390. An object without a 390 is ByLayer. ByBlock isn't written, so it reads back as ByLayer.
• Tables kept in the drawing travel in the CADCRAFT_PLOTSTYLES XRECORD (JSON) of the named object dictionary.