HelpPrinter

HelpPrinter is a helper class that is used to create and print help screen.

Public data members

Style

HelpPrinter.style holds a style that should be applied to the help screen text.

Public member functions

Constructor

Constructor of HelpPrinter initializes an object with specified Style parameter.

Signature

this(Style s)

formatCommandUsage

formatCommandUsage returns formatted string for command usage line which is usually Usage: ....

Signature

string formatCommandUsage(string[] commandName, in CommandHelpInfo helpInfo)

Parameters

commandName
List of command names including names of parent commands starting with top-level command.
helpInfo
Help info about command.

Return value

String with formatted usage info.

formatArgumentUsage

formatArgumentUsage returns formatted string for argument usage (argument representation in command usage line) which is usually string like [--foo FOO].

Signature

string formatArgumentUsage(in ArgumentHelpInfo helpInfo, bool usageString)

Parameters

helpInfo
Help info about argument.
usageString
If true then the returned value wil be used in usage string, otherwise in argument description.

Return value

String with formatted argument usage info.

formatArgumentValue

formatArgumentValue returns formatted string for argument value: --name <value>. For example, it returns [FOO ...] if argument usage is --foo [FOO ...].

Signature

string formatArgumentValue(in ArgumentHelpInfo helpInfo)

Parameters

helpInfo
Help info about argument.

Return value

String with formatted argument value.

createHelpScreen

This function creates HelpScreen based on list of commands.

Signature

HelpScreen createHelpScreen(CommandHelpInfo[] commands)

Parameters

commands
Current stack of (sub)commands starting with top-level command.

Return value

HelpScreen object with all information about help screen.

createSubCommandGroup

Function that creates a HelpScreen.Group group from CommandHelpInfo data.

Signature

HelpScreen.Group createSubCommandGroup(const ref CommandHelpInfo cmd)

Parameters

cmd
Command that contains subcommands.

Return value

HelpScreen.Group object with subcommand entries.

createArgumentsGroups

Function that creates an array of HelpScreen.Group groups from commands data. Usually this function merges groups with the same names from all commands.

Signature

HelpScreen.Group[] createArgumentsGroups(const ref CommandHelpInfo[] commands)

Parameters

commands
Current stack of (sub)commands starting with top-level command.

Return value

Array of HelpScreen.Group objects representing groups of arguments.

printHelp

Function that creates help screen from commands info and prints through sink.

Signature

void printHelp(void delegate(string) sink, CommandHelpInfo[] commands)

Parameters

sink
Delegate that receives output in pieces.
commands
Current stack of (sub)commands starting with top-level command.

printHelpScreen

This function prints HelpScreen object through sink.

Signature

void printHelpScreen(void delegate(string) sink, const ref HelpScreen screen, size_t descriptionOffset)

Parameters

sink
Delegate that receives output in pieces.
screen
Help information to print.
descriptionOffset
Screen offset for parameter description. If help text can be represented as two columns of text, descriptionOffset is the position when the second column should start.

printGroup

This function prints HelpScreen.Group object through sink.

Signature

void printGroup(void delegate(string) sink, const ref HelpScreen.Group group, size_t descriptionOffset)

Parameters

sink
Delegate that receives output in pieces.
group
Group of parameters to print.
descriptionOffset
Screen offset for parameter description. If help text can be represented as two columns of text, descriptionOffset is the position when the second column should start.

printParameter

This function prints HelpScreen.Parameter object through sink.

Signature

  void printParameter(void delegate(string) sink, const ref HelpScreen.Parameter param, size_t descriptionOffset)

Parameters

sink
Delegate that receives output in pieces.
param
Parameter to print.
descriptionOffset
Screen offset for parameter description. If help text can be represented as two columns of text, descriptionOffset is the position when the second column should start.

Public static functions

wrapText

wrapText function wraps text into paragraphs by breaking it up into asequence of lines separated with \n, such that the length of each line does not exceed specific limit. The last line is terminated with \n.

This function is similar to std.string.wrap but with few adjustments:

Styling, if any, is removed during calculation of word length.
Line breaks \n are preserved. This allows having line breaks where needed in addition to those that are added by function itself.
Output is returned via sink in parts rather than in allocated string. Caller can use appender!string if string is needed.

Signature

static void wrapText(void delegate(string) sink,
    string text,
    string firstIndent,
    string indent,
    size_t maxLineLength = 80)

Parameters

sink
Delegate that receives output in pieces.
text
Text to be wrapped.
firstIndent
String used to indent first line.
indent
String used to indent second and following lines.
maxLineLength
Maximum line length.

Last modified: 11 January 2026