What is code folding?

Code folding is when you can take several lines of code and collapse them. Folding is super useful for situations where code takes up space when you do not need to see it for your current editing. Common cases are things like function definitions, for loops, or large tables.

How does Vim handle folding?

Folding Modes

Vim has several folding modes:

manual - you pick where folds go
indent - fold by indented blocks
syntax - fold by semantic markers in code
expr - fold by user expression
marker - fold based on Markers that are placed by a user
diff - used to fold unchanged text when using Views

For the most part, I'm just going to use manual mode. I know enough of the motions that I can get around easier, and plus since I write in a variety of languages things like indent or syntax might not be sufficient or expressive enough.

Creating and Deleting Folds

To create a fold, use zf{motion}, where, you guessed it, you can use just about any of the Motions you like.

Folds can also be created using Visual mode. Select the text, then zf.

zd deletes folds

zD deletes folds recursively. So if you have folds within folds, it will delete those too. If used in visual mode, it will delete all the folds in the window.

zE will eliminate all folds in the current window.

Opening and Closing Folds

There are three main commands: za, zc, and zo. zc and zo close and open folds respectively, and have a recursive cousin using a capital letter instead of the lower case letter. za is different: it is a toggle between open and closed. Recursively, it may be less useful if there is a mixing of open and closed nested folds. zA will switch the the folded status of all of them based on the parent fold (I think.)

There are additional commands for opening and closing folds that may be useful. zm will fold 'more', where it will fold to a certain nested level. zM will close all folds. zr will fold 'less', where it will reveal more. zR will open all folds.

There are two commands that will also change the enabled-ness of folding. zn will open all folds and disable folding, while zN will set all folds back to how they were before, and enable folding again

Moving over folds

[z and ]z will move to the beginning and end of the current open fold, or to the start / end of the parent fold from the child fold. zj and zk will move to the next fold in that direction.zj and zk can also be used with operators before hand (3zj is down 3 folds).

Editing and Commands on Folds

Closed folds act a lot like single lines with commands. dl for example will not delete the current line if on a closed fold, it will delete everything in the fold, period.

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