2Controlling the appearance of diagrams¶

This section describes a number of customization keys defined by this package. All keys are located in the path /tikz/commutative diagrams. Options passed to {tikzcd} or \arrow are searched for in that path, and, if not found there, in /tikz. To set options globally, it is convenient to use the following command.

Besides the keys described in this manual, numerous TikZ parameters can affect the appearance of a diagram. However, only a few of them (namely those appearing in every diagram, every cell, every arrow, and every label below) are reinitialized when {tikzcd} is called. This means that modifying a certain TikZ parameter globally may or may not affect the output of {tikzcd}.

We also point out that besides the options and styles provided by this package, several keys defined by TikZ are useful for arrows. Some examples are dashed, dotted, and its relatives, line width=⟨dimension⟩, color=⟨color⟩, bend right, bend left, in=⟨angle⟩, out=⟨angle⟩, loop, etc. See the pgf manual [2, line styles and to paths]. Likewise, TikZ provides several keys that are useful for labels, such as above, below, left, right, swap (which makes the label be placed on the right side of the arrow, relative to its direction), sloped, pos=⟨fraction⟩, near start, near end, inner sep=⟨dimension⟩, font=⟨font command⟩, text width=⟨dimension⟩, etc. See the pgf manual [2, nodes, esp. label placement].

2.1General options¶

The baseline=0pt setting is used to make equation numbers be placed correctly (as an exception, one-row diagrams are anchored at their matrix base, which is exactly what you want).

The asymmetrical rectangle shape is described in §4.1. The inner xsep, inner ysep options determine the spacing between a diagram entry and any arrows reaching it.

Notice that setting, say, row sep=1cm globally with \tikzcdset will have no effect, since the row sep option is re-set at the beginning of each diagram. To make all diagrams have row sep equal to 1 cm, you can modify the meaning of normal by saying

• \tikzcdset{row sep/normal=1cm}.

You can also create new sizes, but note that pgf requires new keys to be initialized explicitly. For example, to create a size my size, meaning 1 ex, you should use

• \tikzcdset{row sep/my size/.initial=1ex}.

In the examples below, the triangular diagrams would look too wide or too tall if the column or row separation were not set appropriately.

The discussion of matrix spacing in the pgf manual [Tantau] contains further details on the spacing of matrix cells.

The picture below shows the (somewhat subtle) difference between the cramped and the non-cramped styles.

Keep in mind that while there are some legitimate uses for {tikzcd} diagrams on inline formulas, standard LaTeX constructs such as \overset and \xrigthtarrow are often sufficient and should be preferred.

2.2Global options for arrows¶

If you are using a font different from Computer Modern or Latin Modern, you may find the best results by selecting the math font style. As detailed in §4.4, this is not guaranteed to work perfectly with all fonts, but gives good results in many cases. If the math font style gives unsatisfactory results, you can try selecting the tikz style, and setting /tikz/> to the value that best matches your font (among those shown in [2, arrow tips]).

2.3Absolute placement of arrows¶

The usual behavior of \arrow is to produce an arrow starting at the diagram entry where the command appears, and ending at an entry whose location is specified relative to that. The following keys override this behavior, allowing source and target to be selected explicitly.

Recall that it is possible to give a specific entry of a TikZ matrix a name by using the |[⟨options⟩]| syntax, as done for entry \(C\) in the example below. You must be careful not to create nodes whose name contains only the characters l, r, u, d if you want to refer to them using from or to. The following illustrates several different uses of these keys.

In the next examples, empty labels are used to create nodes for later reference. The draw=red option is used to show where these empty nodes are located, but of course you want to remove that when using this technique.

2.4Phantom arrows¶

Sometimes it is necessary to insert a symbol outside the grid subjacent to the diagram. The easiest way to achieve this is as a label to an invisible arrow.

In the picture below, the arrow containing the phantom option goes from \(A\) to \(D\), and the \ulcorner symbol (\(\ulcorner \)) is inserted closer to the starting point \(A\).

2.5Fine-tuning the placement of arrows¶

The default values of shift left and shift right are appropriate for a pair of parallel arrows, and dimensionless arguments are useful to create sets of multiple parallel arrows.

See the picture on §4.1 for some of the possible values for ⟨anchor⟩.

Note that the ends of an arrow can be shortened individually using TikZ’s built-in keys shorten < and shorten >.

2.6Three-dimensional diagrams¶

Note that, since arrows are drawn in the order they are read, it may be necessary to defer the drawing of certain arrows to achieve the desired result. This can be done using the from key, as shown in the following picture.

2.7Options for labels¶

The key /tikz/auto makes the label be placed on the left side of the arrow, relative to its direction. The key /tikz/inner sep controls the distance between a label and the corresponding arrow.