Linetypes

A new drawing’s LTYPE table holds ByBlock, ByLayer and Continuous, none with a pattern.

C++Copy
DxfIO::Document drawing = DxfIO::Create(DxfIO::Version::R2018);
for (const DxfIO::Tables::Ltype &ltype : drawing.Ltype.Records)
{
  std::println("{}: {} elements", ltype.Record.Name, ltype.Dashes.size());
}

textCopy
ByBlock: 0 elements
ByLayer: 0 elements
Continuous: 0 elements

Dashes is the pattern, repeated along the line: a positive Length is a dash, 0 a dot, a negative length a space; a Flags of 0 keeps an element plain, 2 draws Text on it and 4 a shape. The linetype’s own Length is the whole pattern’s, the lengths added without their sign: 10 + 3 + 0 + 3. Edit::Add fails when the table holds a linetype of that name.

C++Copy
DxfIO::Tables::Ltype dashdot{};
dashdot.Record.Name = "DashDot";
dashdot.Description = "__ . __ . __ . __";
dashdot.Length = 16;
dashdot.Dashes = {{.Length = 10}, {.Length = -3}, {.Length = 0}, {.Length = -3}};
DxfIO::Edit::Add(drawing, dashdot);

A layer’s Linetype names the linetype of the entities on it whose own is ByLayer, as a new entity’s is.

C++Copy
DxfIO::Tables::Layer axes{};
axes.Record.Name = "Axes";
axes.Color = 1;
axes.Linetype = DxfIO::Symbol{"DashDot"};
DxfIO::Edit::Add(drawing, axes);

DxfIO::Entities::Line axis{};
axis.Record.Layer = DxfIO::Symbol{"Axes"};
axis.Start = {.X = -50, .Y = 0, .Z = 0};
axis.End = {.X = 250, .Y = 0, .Z = 0};
DxfIO::Edit::Add(drawing, axis);

An entity that names a linetype in Record.Linetype is drawn with it, whatever its layer’s. Edit::Add does not check the name: Audit::Check reports one the table does not hold, and Audit::Repair sets it to ByLayer. Record.Scale scales the pattern for that entity alone: at 2, each dash and space is twice as long.

C++Copy
DxfIO::Entities::Circle hole{};
hole.Center = {.X = 100, .Y = 0, .Z = 0};
hole.Radius = 60;
hole.Record.Linetype = DxfIO::Symbol{"DashDot"};
hole.Record.Scale = 2;
DxfIO::Edit::Add(drawing, hole);

C++Copy
const auto saved = DxfIO::SaveFile(drawing, "linetypes.dxf");
if (!saved)
{
  std::println("{}", saved.error().What);
  return 1;
}