Additional goodies - tikz-cd Manual

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4Additional goodies¶

This package provides some general pgf infrastructure to achieve its goals. These additional goodies are documented in this section.

4.1The `asymmetrical rectangle` shape¶

The following shape is used inside {tikzcd} to ensure that arrows between nodes in the same row are perfectly horizontal, even if the nodes contain text with different heights and depths.

Shape asymmetrical rectangle ¶

This shape is similar to the rectangle shape, but its center is located at a fixed distance of the base, as determined by the center yshift key, rather than lying at the shape’s geometric center. The numerical anchors, as well as east and west, are modified accordingly, and there are anchors called real center, real east, and real west matching rectangle’s original definitions. All other anchors provided by rectangle are available and remain unmodified.

/tikz/commutative diagrams/center yshift=⟨dimension⟩ (no default, initially axis_height) ¶

Determines the distance between asymmetrical rectangle’s base and center anchors.

The picture below shows some of the available anchors.

(-tikz- diagram)

4.2Reading font parameters¶

The following are pgfmath functions used to access relevant math font parameters. They take no arguments, but the result depends of the currently selected font size.

axis_height

Returns the axis height parameter (a.k.a. $\sigma _{22}$) of the document’s math font.

rule_thickness

Returns the fraction rule thickness (a.k.a. $\xi _8$) of the document’s math font.

4.3Computer Modern arrow tips¶

The following arrow tips mimic the Computer Modern designs. It is useful to know that at size 10 pt, the Computer Modern arrow stems are 0.4 pt thick; for other font sizes, scale this parameter accordingly, or set line width=rule_thickness.

Notice that by using the mechanism explained in §1.3, it is not necessary, and in fact not advisable, to directly refer to the arrow tips listed in this section inside a {tikzcd}.

.
`cm to`	yields
`cm implies`	yields
`cm bold to`	yields
`cm double to`	yields
`cm to reversed`	yields

.
`cm bar`	yields
`cm left to`	yields
`cm right to`	yields
`cm left hook`	yields
`cm right hook`	yields

4.4Glyph arrow tips¶

As an attempt to provide a general solution to the problem of having matching arrow tips in text and pictures, this feature produces arrow tips that consist of (pieces of) font glyphs carefully placed at the endpoints of the path. To activate it in {tikzcd} diagrams, refer to the arrow style key.

Arrow Tip Kind Glyph

An arrow tip made from a piece of text. It accepts the following parameters.

/pgf/arrow keys/glyph math command=⟨name⟩(no default) ¶

The name of a command (to be used inside $\csname …\endcsname$) producing the desired glyph.

/pgf/arrow keys/glyph length=⟨dimension⟩ (no default, initially 1ex) ¶

The length of the portion of the glyph not clipped away. Also used to set the ‘tip end’ parameter.

/pgf/arrow keys/glyph axis=⟨dimension⟩ (no default, initially axis_height) ¶

A vertical displacement applied to the glyph in order to make the glyph’s central axis (typically an arrow stem) aligned with the path.

/pgf/arrow keys/glyph shorten=⟨dimension⟩ (no default, initially -0.1ex) ¶

An additional amount by which the end of the path is shortened. This is used to compensate for the gap that usually exists between the tip end and the glyph’s bounding box.

Below are some usage examples. Notice that glyph arrow tips do not scale with pgf line width but their size depends on the current font size, so you will probably want to set line width=rule_thickness when using them. Also, contrarily to the arrow parameters defined by the arrows.meta library, the parameters described above are evaluated only at the time the arrow tip is drawn, so they can (and should) be given in the units em or ex.

It is important to be aware of some drawbacks of this feature. First, the transition between a line and the arrow tip may become visible with some printers (especially in low resolutions or draft mode) and document viewers, as you may be able to see in the samples above. Second, these rather long tips may ( (-tikz- diagram) ) or may not ( ) fit nicely with dashed or curved lines. Finally, the method used to place the arrow tip at the end of a stroked path and clip away the arrow stem makes certain assumptions about the font design and could fail in cases where unusual design choices are made.

References¶

[Milne] James Milne, Guide to commutative diagrams. Available at http://www.jmilne.org/not/CDGuide.html.
[Tantau] Till Tantau, The TikZ and pgf packages: Manual for version 3.1.9. Available at http://mirrors.ctan.org/graphics/pgf/base/doc/pgfmanual.pdf.