a:ln (Line Properties)

Specifies stroke/outline properties for shapes, including width, color, dash style, and line end/join styles.

Parent elements

Child elements

Description

a:ln (Line Properties) is the comprehensive stroke/outline container for DrawingML. It is defined in ECMA-376 Part 1 §20.1.2.2.13 and controls all visual properties of a line or shape outline, including width, color, dash pattern, end caps, and joins.

Purpose and Scope

Line properties control the appearance of:

Shape outlines — Borders of rectangles, circles, polygons
Connectors — Lines and arrows connecting shapes
Text underlines — Text run decorations
Table borders — Cell and table grid lines
Path strokes — Custom geometry outlines

Line properties consist of three groups:

Stroke Appearance — Width, color (fill), and dash pattern
End Styling — Line cap style, arrow heads/tails
Join Styling — How corners/joins are rendered

Rendering Workflow

Determine stroke width — Read w attribute
Determine stroke color — Read fill child element
Determine stroke pattern — Read dash style
Determine end caps — Read cap attribute
Determine joins — Read join element (round, bevel, miter)
Determine arrow heads — Read a:headEnd/a:tailEnd
Render — Paint outline with all properties applied

Attributes

Attribute	Type	Range	Default	Description
`w`	Integer (EMU)	0–20116800	12700	Stroke width in EMUs. 12700 = 1pt. 0 = hairline.
`cap`	Enum	`flat`, `rnd`, `sq`	`flat`	Line cap style at ends: flat, round, or square.
`cmpd`	Enum	`sng`, `dbl`, `dblDot`, `thickThin`, `thinThick`, `tri`	`sng`	Compound line: single, double, triple, or mixed.
`algn`	Enum	`ctr`, `in`	`ctr`	Pen alignment: centered on edge or inside edge.
`prstDash`	Enum	`solid`, `sysDot`, `dash`, `lgDash`, `dashDot`, `lgDashDot`, `lgDashDotDot`	`solid`	Preset dash pattern.

Content Model

a:ln (attributes)
├─ Fill (one of, 0–1)
│  ├─ a:solidFill (solid color)
│  ├─ a:gradFill (gradient)
│  ├─ a:pattFill (pattern)
│  └─ a:noFill (no stroke)
├─ a:prstDash (Preset Dash Pattern, 0–1)
├─ a:custDash (Custom Dash Pattern, 0–1)
├─ a:round (Round Join, 0–1)
├─ a:bevel (Bevel Join, 0–1)
├─ a:miter (Miter Join, 0–1)
├─ a:headEnd (Arrow Head, 0–1)
├─ a:tailEnd (Arrow Tail, 0–1)
├─ a:prstShadow (Preset Shadow, 0–1)
├─ a:outerShdw (Outer Shadow, 0–1)
└─ a:extLst (Extension List, 0–1)

Child Elements

Element	Occurrence	Purpose
Fill element	0–1	Stroke color: solid, gradient, pattern, or no fill
`a:prstDash`	0–1	Preset dash pattern (solid, dash, dot, etc.)
`a:custDash`	0–1	Custom dash pattern (user-defined dashes/gaps)
Join element	0–1	Line join style: round, bevel, or miter
`a:headEnd`	0–1	Arrow head at start of line
`a:tailEnd`	0–1	Arrow tail at end of line

Examples

Simple Solid Black Outline

<a:ln w="12700">
  <a:solidFill>
    <a:srgbClr val="000000"/>
  </a:solidFill>
</a:ln>

var line = new Outline { Width = 12700 };  // 1pt
line.Append(new SolidFill(
  new RgbColorModelHex { Val = "000000" }));  // Black

Dashed Line with Round Caps

<a:ln w="25400" cap="rnd">
  <a:solidFill>
    <a:srgbClr val="0070C0"/>
  </a:solidFill>
  <a:prstDash val="dash"/>
  <a:round/>
</a:ln>

var line = new Outline { Width = 25400, Cap = LineCapValues.Round };  // 2pt, round ends
line.Append(new SolidFill(
  new RgbColorModelHex { Val = "0070C0" }));  // Blue
line.Append(new PresetDash { Val = PresetLineDashValues.Dash });
line.Append(new Round());

Double Line with Bevel Joins

<a:ln w="38100" cmpd="dbl">
  <a:solidFill>
    <a:schemeClr val="accent1"/>
  </a:solidFill>
  <a:prstDash val="solid"/>
  <a:bevel/>
</a:ln>

var line = new Outline { Width = 38100, CompoundLine = CompoundLineValues.Double };  // 3pt double line
line.Append(new SolidFill(
  new SchemeColor { Val = SchemeColorValues.Accent1 }));  // Theme color
line.Append(new PresetDash { Val = PresetLineDashValues.Solid });
line.Append(new Bevel());

Line with Gradient Stroke and Arrow Heads

<a:ln w="19050" cap="rnd">
  <a:gradFill>
    <a:gsLst>
      <a:gs pos="0"><a:srgbClr val="FF6B6B"/></a:gs>
      <a:gs pos="100000"><a:srgbClr val="FFD93D"/></a:gs>
    </a:gsLst>
    <a:lin ang="2700000" scaled="1"/>
  </a:gradFill>
  <a:prstDash val="solid"/>
  <a:round/>
  <a:headEnd type="triangle" w="381000" len="342900"/>
  <a:tailEnd type="triangle" w="381000" len="342900"/>
</a:ln>

var line = new Outline { Width = 19050, Cap = LineCapValues.Round };  // 1.5pt, round ends

// Gradient red-to-yellow
var gradFill = new GradientFill();
var gsLst = new GradientStopList();
gsLst.Append(new GradientStop { Position = 0 }
  .Append(new RgbColorModelHex { Val = "FF6B6B" }));
gsLst.Append(new GradientStop { Position = 100000 }
  .Append(new RgbColorModelHex { Val = "FFD93D" }));
gradFill.Append(gsLst);
gradFill.Append(new LinearGradientFill { Angle = 2700000, Scaled = true });
line.Append(gradFill);

line.Append(new PresetDash { Val = PresetLineDashValues.Solid });
line.Append(new Round());

// Arrow heads
var headEnd = new LineEndProperties { Type = LineEndType.Triangle, Width = 381000, Length = 342900 };
var tailEnd = new LineEndProperties { Type = LineEndType.Triangle, Width = 381000, Length = 342900 };
line.Append(headEnd);
line.Append(tailEnd);

Dotted Line with Square Caps (No Fill Interior)

<a:ln w="12700" cap="sq">
  <a:solidFill>
    <a:srgbClr val="70AD47"/>
  </a:solidFill>
  <a:prstDash val="sysDot"/>
  <a:miter/>
</a:ln>

var line = new Outline { Width = 12700, Cap = LineCapValues.Square };  // Square ends
line.Append(new SolidFill(
  new RgbColorModelHex { Val = "70AD47" }));  // Green
line.Append(new PresetDash { Val = PresetLineDashValues.SystemDot });
line.Append(new Miter());

Thick 3-Point Line with Inside Alignment

<a:ln w="38100" algn="in">
  <a:solidFill>
    <a:srgbClr val="2F5233"/>
  </a:solidFill>
  <a:prstDash val="solid"/>
  <a:round/>
</a:ln>

var line = new Outline { Width = 38100, Alignment = PenAlignmentValues.Inside };  // 3pt, inside edge
line.Append(new SolidFill(
  new RgbColorModelHex { Val = "2F5233" }));  // Dark green
line.Append(new PresetDash { Val = PresetLineDashValues.Solid });
line.Append(new Round());

Thin Double-Dotted Line

<a:ln w="19050" cmpd="dblDot">
  <a:solidFill>
    <a:schemeClr val="accent2"/>
  </a:solidFill>
  <a:prstDash val="solid"/>
  <a:bevel/>
</a:ln>

var line = new Outline { Width = 19050, CompoundLine = CompoundLineValues.DoubleDot };  // Double-dotted
line.Append(new SolidFill(
  new SchemeColor { Val = SchemeColorValues.Accent2 }));
line.Append(new PresetDash { Val = PresetLineDashValues.Solid });
line.Append(new Bevel());

Line Width Reference (EMU)

EMU	Points	Inches	Thickness	Use Case
0	Hairline	<0.01”	Thinnest visible	Grid lines, subtle borders
6350	0.5pt	0.007”	Very thin	Light guides, subtle outlines
12700	1pt	0.014”	Thin	Standard borders, default
19050	1.5pt	0.021”	Medium-thin	Emphasized lines
25400	2pt	0.028”	Medium	Prominent borders
38100	3pt	0.042”	Bold	Strong emphasis
50800	4pt	0.056”	Very bold	Heavyweight borders
76200	6pt	0.084”	Heavy	Title/section separators

Dash Pattern Reference

Preset	Appearance	Use Case
`solid`	———	Standard borders, outlines (most common)
`sysDot`	· · ·	Light dotted lines, grid
`dash`	– – –	Dashed lines, placeholder outlines
`lgDash`	—– —–	Long dashes, section breaks
`dashDot`	–·–·–	Dash-dot pattern, technical drawings
`lgDashDot`	—–·—–·	Long dash-dot, emphasis
`lgDashDotDot`	—–··—–·	Long dash-dot-dot, decorative

Line Cap (End Style)

Cap Value	Appearance	Use Case
`flat`	Straight cut	Default, technical drawings
`rnd`	Rounded end	Smooth, decorative, modern
`sq`	Square end	Geometric, technical, formal

Line Join (Corner Style)

Join	Appearance	Use Case
`round`	Rounded corners	Smooth, modern designs
`bevel`	Cut diagonal	Technical, geometric
`miter`	Sharp point (with limit)	Default for sharp corners

Compound Line Patterns

Compound	Pattern	Visual	Use Case
`sng`	Single line	———	Standard, default
`dbl`	Double line	═══	Emphasis, section breaks
`tri`	Triple line	═╪═	Strong emphasis, decorative
`thickThin`	Thick + thin	═─	Asymmetric emphasis
`thinThick`	Thin + thick	─═	Asymmetric emphasis (reversed)
`dblDot`	Double dotted	·:·:	Subtle double, grid

Arrow Head Types

Type	Shape	Use Case
`none`	No arrow	Lines, connectors without direction
`triangle`	▶ Filled triangle	Standard arrows, flow diagrams
`stealth`	► Stealth/modern	Modern diagrams, slick appearance
`open`	⊳ Open triangle	Light emphasis, outline style
`oval`	⚫ Circle	Flowcharts, markers
`diamond`	◆ Diamond	Network diagrams, special nodes

Notes

Element Relationships

Parents (8 container elements):
- a:spPr (shape properties): Primary shape outline.
- a:txBody (text body): Outline around text/characters (rarely used).
- a:tblPr (table properties): Default line style for table borders.
- Lines (a:lnL, a:lnR, a:lnT, a:lnB): Individual borders on table cells (left, right, top, bottom).
Children (optional stroke definition elements):
- Fill: a:solidFill, a:gradFill, a:pattFill, a:noFill (zero or one) for line color/gradient
- Dash: a:prstDash (preset dash pattern) or a:custDash (custom dash pattern)
- Joins: a:round, a:bevel, a:miter (line join style—corners)
- Endings: a:headEnd (arrow head), a:tailEnd (arrow tail) for line decorations

General Notes

Width Units: EMU (English Metric Units); 914400 EMU = 1 inch = 72pt. Common: 12700 = 1pt, 25400 = 2pt, 38100 = 3pt.
Outline vs Border: In DrawingML context, a:ln is a line stroke around shape/text geometry, not a table border. Table borders use individual cell lines (a:lnL, a:lnR, a:lnT, a:lnB).
No Stroke: Use a:noFill as child element to render shape with no outline (invisible border).
Single Stroke Definition: A shape can have only one outline. Multiple a:ln elements are invalid; use groups or connectors for multi-stroke effects.
Dash Patterns: a:prstDash (preset) or a:custDash (custom) define stroke pattern. Preset is most common.
Color Gradient: Line fills can be solid, gradient, or pattern—not just single colors. Gradients flow along the stroke direction.
Arrow Heads: a:headEnd and a:tailEnd add arrows or other line endings (circles, diamonds, etc.). Only applicable to connector shapes.
Line Joins: Line join styles (a:round, a:bevel, a:miter) control how line segments connect (corners). Default is miter.
Compatibility: Line properties structure is consistent across all Office formats supporting shapes (Presentation, Drawing, Spreadsheet).