acad-linetypes-textstyles

name	acad-linetypes-textstyles
description	Linetype and text style creation, loading from .lin files, TrueType/SHX fonts

AutoCAD Linetypes and Text Styles

Use this skill when creating, loading, or modifying linetypes and text styles — accessing linetype and text style tables, loading linetypes from .lin files, configuring linetype scale variables, creating text styles with TrueType or SHX fonts, and setting up complex linetypes that embed text or shape elements.

Linetype Table Access

Database db = doc.Database;
using (Transaction tr = db.TransactionManager.StartTransaction())
{
    LinetypeTable ltt = (LinetypeTable)tr.GetObject(db.LinetypeTableId, OpenMode.ForRead);

    // Check if a linetype exists (case-insensitive)
    bool exists = ltt.Has("DASHED");

    // Get linetype by name
    ObjectId ltId = ltt["DASHED"];
    LinetypeTableRecord ltr = (LinetypeTableRecord)tr.GetObject(ltId, OpenMode.ForRead);

    // Enumerate all linetypes
    foreach (ObjectId id in ltt)
    {
        LinetypeTableRecord rec = (LinetypeTableRecord)tr.GetObject(id, OpenMode.ForRead);
        if (rec.IsDependent) continue;  // skip xref linetypes
        ed.WriteMessage($"\n{rec.Name}: {rec.AsciiDescription}");
    }

    tr.Commit();
}

System Linetypes

Three linetypes are always present and cannot be deleted:

ObjectId byLayerId = db.ByLayerLinetype;       // entities inherit from layer
ObjectId byBlockId = db.ByBlockLinetype;       // entities inherit from block reference
ObjectId continuousId = db.ContinuousLinetype; // solid unbroken line

// Current entity linetype (CELTYPE sysvar)
ObjectId currentId = db.Celtype;
db.Celtype = ltt["HIDDEN"];  // set current linetype for new entities

Loading Linetypes from .lin Files

// Load a single linetype by name from a .lin file
db.LoadLineTypeFile("HIDDEN", "acad.lin");
db.LoadLineTypeFile("HIDDEN2", "acadiso.lin");  // metric
db.LoadLineTypeFile("MY_LINETYPE", @"C:\Standards\custom.lin");  // custom file

Safe Load with Existence Check

private static ObjectId EnsureLinetypeLoaded(
    Database db, Transaction tr, string linetypeName, string linFile = "acad.lin")
{
    LinetypeTable ltt = (LinetypeTable)tr.GetObject(db.LinetypeTableId, OpenMode.ForRead);
    if (ltt.Has(linetypeName))
        return ltt[linetypeName];

    try
    {
        db.LoadLineTypeFile(linetypeName, linFile);
    }
    catch (Autodesk.AutoCAD.Runtime.Exception ex)
        when (ex.ErrorStatus == ErrorStatus.FilerError)
    {
        return db.ContinuousLinetype;  // .lin file not found
    }
    catch (Autodesk.AutoCAD.Runtime.Exception ex)
        when (ex.ErrorStatus == ErrorStatus.DuplicateKey)
    {
        // Already loaded (race condition)
    }

    ltt = (LinetypeTable)tr.GetObject(db.LinetypeTableId, OpenMode.ForRead);
    return ltt.Has(linetypeName) ? ltt[linetypeName] : db.ContinuousLinetype;
}

Reading Dash Pattern Elements

for (int i = 0; i < ltr.NumDashes; i++)
{
    double dashLength = ltr.DashLengthAt(i);      // positive=dash, negative=gap, zero=dot
    int shapeNumber = ltr.ShapeNumberAt(i);        // 0 for simple dashes; nonzero for shape elements
    ObjectId shapeStyleId = ltr.ShapeStyleAt(i);   // text style or shape-file style
    string textAt = ltr.TextAt(i);                 // non-empty for text elements
    double shapeScale = ltr.ShapeScaleAt(i);
    double shapeRotation = ltr.ShapeRotationAt(i);
    Vector2d shapeOffset = ltr.ShapeOffsetAt(i);
    bool ucsOriented = ltr.ShapeIsUcsOrientedAt(i);
}

Simple vs Complex Linetypes

Simple Linetypes

Simple linetypes contain only dashes, gaps, and dots — defined purely by numeric values:

;; .lin file definition
*DASHED,Dashed __ __ __ __
A,.5,-.25

All dash elements have ShapeNumberAt(i) == 0 and TextAt(i) == "".

Complex Linetypes — Text Elements

Complex linetypes embed text characters within the dash-gap pattern. The text element references a text style.

*HOT_WATER_SUPPLY,Hot water supply ----HW----HW----
A,.5,-.2,["HW",STANDARD,S=.1,R=0.0,X=-0.1,Y=-.05],-.2

Text elements appear as dash entries where TextAt(i) returns a non-empty string. ShapeStyleAt(i) returns the text style ObjectId used for rendering.

Complex Linetypes — Shape Elements

Shape elements reference SHX shapes via a text style with IsShapeFile = true:

*FENCELINE1,Fenceline circle ----0-----0----0-----0----
A,.25,-.1,[CIRC1,ltypeshp.shx,x=-.1,s=.1],-.1,1

Shape elements have ShapeNumberAt(i) != 0. ShapeStyleAt(i) returns the shape-file text style ObjectId.

Creating Linetypes Programmatically

LinetypeTable ltt = (LinetypeTable)tr.GetObject(db.LinetypeTableId, OpenMode.ForWrite);

LinetypeTableRecord ltr = new LinetypeTableRecord();
ltr.Name = "MY_DASH_DOT";
ltr.AsciiDescription = "Custom dash dot __.__.__";
ltr.NumDashes = 4;
ltr.SetDashLengthAt(0, 0.5);    // dash (positive)
ltr.SetDashLengthAt(1, -0.25);  // gap (negative)
ltr.SetDashLengthAt(2, 0.0);    // dot (zero)
ltr.SetDashLengthAt(3, -0.25);  // gap

ltt.Add(ltr);
tr.AddNewlyCreatedDBObject(ltr, true);

Complex Linetype with Text

LinetypeTableRecord ltr = new LinetypeTableRecord();
ltr.Name = "GAS_LINE";
ltr.AsciiDescription = "Gas line ----GAS----GAS----";
ltr.NumDashes = 3;

ltr.SetDashLengthAt(0, 0.75);                                    // dash
ltr.SetDashLengthAt(1, -0.45);                                   // gap (holds text)
ltr.SetTextAt(1, "GAS");
ltr.SetShapeStyleAt(1, tst["STANDARD"]);                         // text style
ltr.SetShapeScaleAt(1, 0.1);
ltr.SetShapeRotationAt(1, 0.0);
ltr.SetShapeOffsetAt(1, new Vector2d(-0.1, -0.05));
ltr.SetShapeIsUcsOrientedAt(1, false);
ltr.SetDashLengthAt(2, -0.2);                                    // trailing gap

ltt.UpgradeOpen();
ltt.Add(ltr);
tr.AddNewlyCreatedDBObject(ltr, true);

Linetype Scale System Variables

LTSCALE — Global Linetype Scale

double ltscale = db.Ltscale;   // read
db.Ltscale = 1.0;              // set (also: Application.SetSystemVariable("LTSCALE", 1.0))

CELTSCALE — Current Entity Linetype Scale

double celtscale = db.Celtscale;  // read
db.Celtscale = 0.5;               // new entities get LinetypeScale = 0.5

// Per-entity override (baked at creation from CELTSCALE, editable after)
entity.LinetypeScale = 2.0;

PSLTSCALE — Paper Space Linetype Scale

// 1 = scale linetypes in viewports to match paper space appearance
// 0 = display at model space scale
Application.SetSystemVariable("PSLTSCALE", (short)1);

Effective scale for an entity = LTSCALE * Entity.LinetypeScale (CELTSCALE is baked into Entity.LinetypeScale at creation time.)

Assigning Linetypes to Entities

Line line = new Line(pt1, pt2);
line.LinetypeId = ltt["HIDDEN"];         // specific linetype
line.LinetypeId = db.ByLayerLinetype;    // inherit from layer (default)
line.LinetypeId = db.ByBlockLinetype;    // inherit from block reference
line.LinetypeScale = 0.5;               // per-entity scale

TextStyleTable Access

TextStyleTable tst = (TextStyleTable)tr.GetObject(db.TextStyleTableId, OpenMode.ForRead);

bool exists = tst.Has("MyStyle");
ObjectId styleId = tst["MyStyle"];
TextStyleTableRecord style = (TextStyleTableRecord)tr.GetObject(styleId, OpenMode.ForRead);

// Current text style
ObjectId currentStyleId = db.Textstyle;
db.Textstyle = tst["STANDARD"];  // set current

// Enumerate (skip xref and shape-file styles)
foreach (ObjectId id in tst)
{
    TextStyleTableRecord rec = (TextStyleTableRecord)tr.GetObject(id, OpenMode.ForRead);
    if (rec.IsDependent || rec.IsShapeFile) continue;
    ed.WriteMessage($"\n{rec.Name}: {rec.FileName}");
}

Creating Text Styles

TrueType Font Style

TextStyleTable tst = (TextStyleTable)tr.GetObject(db.TextStyleTableId, OpenMode.ForWrite);

TextStyleTableRecord style = new TextStyleTableRecord();
style.Name = "ARIAL_NARROW";
style.FileName = "arialn.ttf";
style.BigFontFileName = "";
style.TextSize = 0.0;           // 0 = variable height (set per entity)
style.XScale = 1.0;             // width factor
style.ObliquingAngle = 0.0;
style.IsVertical = false;

ObjectId styleId = tst.Add(style);
tr.AddNewlyCreatedDBObject(style, true);

// Alternative: use FontDescriptor for TrueType
style.Font = new FontDescriptor("Arial Narrow", false, false, 0, 0);
//                               typeface        bold   italic charset pitch

SHX Font Style

TextStyleTableRecord style = new TextStyleTableRecord();
style.Name = "ROMANS_STYLE";
style.FileName = "romans.shx";
style.BigFontFileName = "";            // set for CJK (e.g., "bigfont.shx")
style.TextSize = 2.5;                 // fixed height
style.XScale = 0.8;
style.ObliquingAngle = 0.2618;        // ~15 degrees

tst.UpgradeOpen();
tst.Add(style);
tr.AddNewlyCreatedDBObject(style, true);

Detecting Font Type

FontDescriptor fd = style.Font;
bool isTrueType = !string.IsNullOrEmpty(fd.TypeFace);
bool isShx = style.FileName.EndsWith(".shx", StringComparison.OrdinalIgnoreCase);

// TrueType: fd.TypeFace = "Arial", fd.Bold, fd.Italic, fd.CharacterSet, fd.PitchAndFamily
// SHX: fd.TypeFace is empty, FileName is the .shx path

TrueType vs SHX Fonts

Aspect	TrueType (.ttf)	SHX (.shx)
Rendering	Filled outlines	Stroke-based vectors
PDF export	Embedded as fonts	Converted to geometry
Big fonts	Not supported	Supported via BigFontFileName
Performance	Slower for many entities	Faster for many entities
Font property	Populated TypeFace	Empty TypeFace

Common SHX: txt.shx, simplex.shx, romans.shx, complex.shx, monotxt.shx, isocp.shx

Loading SHX Shapes for Complex Linetypes

Complex linetypes that embed shapes need a text style with IsShapeFile = true:

private static ObjectId EnsureShapeFileStyle(
    Database db, Transaction tr, string shxFileName)
{
    TextStyleTable tst = (TextStyleTable)tr.GetObject(
        db.TextStyleTableId, OpenMode.ForRead);

    // Check if a matching shape-file style already exists
    foreach (ObjectId id in tst)
    {
        TextStyleTableRecord existing = (TextStyleTableRecord)tr.GetObject(
            id, OpenMode.ForRead);
        if (existing.IsShapeFile &&
            existing.FileName.Equals(shxFileName, StringComparison.OrdinalIgnoreCase))
            return id;
    }

    // Create new shape-file style
    tst.UpgradeOpen();
    TextStyleTableRecord shapeStyle = new TextStyleTableRecord();
    shapeStyle.Name = Path.GetFileNameWithoutExtension(shxFileName).ToUpperInvariant();
    shapeStyle.FileName = shxFileName;   // e.g., "ltypeshp.shx"
    shapeStyle.IsShapeFile = true;
    shapeStyle.TextSize = 0.0;

    ObjectId newId = tst.Add(shapeStyle);
    tr.AddNewlyCreatedDBObject(shapeStyle, true);
    return newId;
}

Standard shape files: ltypeshp.shx (circles, boxes, diamonds), gdt.shx (GD&T symbols).

Gotchas

• db.LoadLineTypeFile() throws if the name is not in the .lin file — always try/catch; also throws DuplicateKey if already loaded
• System linetypes (ByLayer, ByBlock, Continuous) cannot be deleted, renamed, or modified
• LinetypeTable.Has() is case-insensitive
• PatternLength is read-only — computed from sum of absolute dash lengths
• NumDashes must be set before SetDashLengthAt() — it allocates the internal array
• Dot elements use dash length of exactly 0.0 (not a small positive number)
• Complex text elements require the referenced text style to exist — missing style = text won't render
• Complex shape elements require a text style with IsShapeFile = true — not a regular text style
• Shape-file text styles appear in TextStyleTable but are hidden from user-facing style list
• FileName accepts just the file name (arial.ttf, romans.shx) — AutoCAD resolves from its fonts/support paths
• TextSize = 0.0 means variable height — non-zero forces all entities to that fixed height
• ObliquingAngle is in radians, not degrees
• The STANDARD text style always exists and cannot be deleted, but can be modified
• db.Textstyle (lowercase 's') is the current text style ObjectId — not TextStyleTableId
• PSLTSCALE only takes effect after REGEN in each viewport
• Entity.LinetypeScale incorporates CELTSCALE from creation — changing CELTSCALE later does not update existing entities

Related Skills

• acad-layers — linetype assignment on layers via LinetypeObjectId property
• acad-mtext — text style usage in MText and DBText entities
• acad-dimensions — dimension styles reference text styles for dimension text formatting
• acad-polylines — linetypes applied to polylines; linetype generation (PLINEGEN) across vertices