Prompt a set of possible options

Question

Recent versions of Mathematica dynamically prompt a list of possible options. For example, when typing

Plot[x, {x,0,1}, PlotStyle->

After typing the arrow, Mathematica prompt a list Gray, Dashed, Thick for choice. How to define similar behavior for user defined functions? For example,

Options[myFun] = {myOpt -> value};
myFun[OptionsPattern[]] := 1;

How to prompt a set of possible options, like opt1, opt2, opt3 right after typing

myFun[myOpt->

Answer 1

Thanks for asking this question; I might not have discovered this customizable area without it.

The auto-completion option values are automatically loaded on Front End start from:

FileNameJoin[{$InstallationDirectory, "SystemFiles", "FrontEnd",
  "SystemResources", "FunctionalFrequency", "OptionValues"}]

This directory contains a series of Package (.m) files each with the name of a function, e.g. ArrayPlot.m. The file name itself determines that this will apply to the function ArrayPlot. It also contains an additional file that appears to apply to all functions: CommonOptions.m

The structure of each file is a list of Rules:

{Extension -> {"Automatic"}, Trig -> {"True", "False"}}

• The right hand side of each rule is always a list of Strings or an empty list {}
• Option values that are actual strings must be escaped: "\"string\""
• Option names must be Symbols (thanks Kuba)

A special Rule form exists for icons within the menu, e.g. from ArrayPlot.m:

PlotTheme ->
 {{"\"Web\"", "PlotTheme-ArrayPlot-Web.png"},
  {"\"Minimal\"", "PlotTheme-ArrayPlot-Minimal.png"},
  {"\"Detailed\"", "PlotTheme-ArrayPlot-Detailed.png"},
  {"\"Business\"", "PlotTheme-ArrayPlot-Business.png"},
  {"\"Marketing\"", "PlotTheme-ArrayPlot-Marketing.png"},
  {"\"Scientific\"", "PlotTheme-ArrayPlot-Scientific.png"},
  {"\"Monochrome\"", "PlotTheme-ArrayPlot-Monochrome.png"},
  {"\"Classic\"", "PlotTheme-ArrayPlot-Classic.png"},
  {"\"Default\"", "PlotTheme-ArrayPlot-Default.png"}}

Each of these icon files reside in:

FileNameJoin @ {$InstallationDirectory, "SystemFiles", "FrontEnd", 
  "SystemResources", "Bitmaps", "Popups", "CodeCompletion", "Thumbnails"}

I have not checked to see if other paths are also searched.

As an example I created a new file foo.m in the OptionValues directory with the content:

{myOption -> {"Doc", "Grumpy", "Happy", "Sleepy", "Bashful", "Sneezy", "Dopey"}}

Now after (re)starting Mathematica: