# Paratick

Categories: generativepy generative art

The `ParallelMarker`

class is a special Shape that adds a small arros marker to a line, of the type often used in geometric diagrams to show that two lines are parallel. They look like this:

You can add 1, 2 or 3 markers.

The `TickMarker`

only draws the tick, it doesn't draw the line itself. This would normally be draw using a Line object, Polygon object, or similar.

## ParallelMarker class

`ParallelMarker`

is derived from the `Shape`

class. It adds several methods:

`of_start_end`

`with_length`

`with_count`

`with_gap`

### of_start_end

Creates a marker based on a start and end points.

```
of_start_end(a, b)
```

Parameter | Type | Description |
---|---|---|

a | (number, number) | Tuple (x, y) for start of line |

b | (number, number) | Tuple (x, y) for end of line |

This will draw an tick marker for the line formed by **ab**. The marker will be halfway between points `a`

and `b`

, and the arrow will point towards `b`

.

### with_length

Sets the length of the marker.

```
with_length(length)
```

Parameter | Type | Description |
---|---|---|

length | number | Length of marker in user units. |

The default is 4.

### with_count

Sets the number of arrows in the marker.

```
with_count(count)
```

Parameter | Type | Description |
---|---|---|

count | int | Number of arrows |

This can be used to draw a single, double, or triple arrows. Permitted values are 1, 2, or 3. Default is 1.

### with_gap

Sets the gap between the arrows if `count > 1`

.

```
with_gap(gap)
```

Parameter | Type | Description |
---|---|---|

gap | number | Gap between arrows in user units. |

Sets the spacing of the arrows. This is only relevant if there is more than one arrow (ie if `count > 1`

), otherwise it is ignored. The default is 1.

## paratick function

This older `paratick`

function is deprecated as of GenerativePy 3.1.

```
paratick(ctx, a, b, count=1, length=4, gap=1)
```

Parameter | Type | Description |
---|---|---|

ctx | Context | The Pycairo Context to draw to |

a | (number, number) | Tuple (x, y) for point a |

b | (number, number) | Tuple (x, y) for point b |

count | int | Number of ticks on the line, 1, 2 or 3. |

length | number | length of the tick in user units. |

gap | number | Gap between ticks in user units. |

Draws an tick across the line ab. The tick is half way between points `a`

and `b`

, and points towards `b`

.

## Example

See the example in the angle_marker article.

## See also

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