feat(markdown): Docs for utils.mergeOptions()

markdown/dev/reference/api/en.md

@@ -74,6 +74,7 @@ The following named exports are **utility methods**:
 | `lineIntersectsCircle`    | See the [lineIntersectsCircle](/reference/api/utils/lineintersectscircle) documentation |
 | `lineIntersectsCurve`     | See the [lineIntersectsCurve](/reference/api/utils/lineintersectscurve) documentation |
 | `linesIntersect`          | See the [linesIntersect](/reference/api/utils/linesintersect) documentation |
+| `mergeOptions`            | See the [mergeOptions](/reference/api/utils/mergeoptions) documentation |
 | `pctBasedOn`              | See the [pctBasedOn](/reference/api/utils/pctbasedon) documentation |
 | `pointOnBeam`             | See the [pointOnBeam](/reference/api/utils/pointonbeam) documentation |
 | `pointOnCurve`            | See the [pointOnCurve](/reference/api/utils/pointoncurve) documentation |

markdown/dev/reference/api/part/config/options/pct/toabs/en.md

@@ -17,16 +17,23 @@ The `toAbs` property should hold a function with the following
 signature:
 
 ```js
-function toAbs(percentage, settings) {
+function toAbs(percentage, settings, mergeOptions) {
   // return value in millimeter here
 }
 ```
 
 The first parameter is the percentage value provided by the user (for example
 `0.5` for `50%`).
+
 The second parameter holds the pattern's [settings](/reference/settings) object
 which holds -- among other things -- the measurements provided by the user.
 
+The third parameter should be the return value of
+[utils.mergeOptions()](/reference/api/utils/mergeoptions), which provides an
+object with all option values populated. Although this parameter is not
+required for simple values based on measurements, it is often required when the
+result depends on several options.
+
 ## Example
 
 In our example above, let's say that the `chestEase` option is

markdown/dev/reference/api/utils/mergeoptions/en.md

@@ -0,0 +1,27 @@
+---
+title: utils.mergeOptions()
+---
+
+The `utils.mergeOptions()` function merges the user-provided options with the
+options from the pattern configuration.
+
+## Signature
+
+```js
+float deg2rad(object settings, object optionsConfig)
+```
+
+## Notes
+
+Typically the only options that are passed as part of settings to the pattern
+are those that differ from the defaults.  This means that if you want to check
+an option outside a draft method, you need to check whether the option is set,
+and if it's not get the default value from the pattern config. Furthermore,
+where the default is stored and whether or not it should be further transformed
+depends on the option type.
+
+This method exists to facilitate this. You pass it the user-provided settings,
+and the pattern config options key, and it will return an object where all
+options are populated with the user-provided values, or their defaults if the
+user did not provide any input.
+