diff options
Diffstat (limited to 'flag.go')
| -rw-r--r-- | flag.go | 82 |
1 files changed, 78 insertions, 4 deletions
@@ -487,9 +487,76 @@ func UnquoteUsage(flag *Flag) (name string, usage string) { return } -// FlagUsages Returns a string containing the usage information for all flags in -// the FlagSet -func (f *FlagSet) FlagUsages() string { +// Splits the string `s` on whitespace into an initial substring up to +// `i` runes in length and the remainder. Will go `slop` over `i` if +// that encompasses the entire string (which allows the caller to +// avoid short orphan words on the final line). +func wrapN(i, slop int, s string) (string, string) { + if i+slop > len(s) { + return s, "" + } + + w := strings.LastIndexAny(s[:i], " \t") + if w <= 0 { + return s, "" + } + + return s[:w], s[w+1:] +} + +// Wraps the string `s` to a maximum width `w` with leading indent +// `i`. The first line is not indented (this is assumed to be done by +// caller). Pass `w` == 0 to do no wrapping +func wrap(i, w int, s string) string { + if w == 0 { + return s + } + + // space between indent i and end of line width w into which + // we should wrap the text. + wrap := w - i + + var r, l string + + // Not enough space for sensible wrapping. Wrap as a block on + // the next line instead. + if wrap < 24 { + i = 16 + wrap = w - i + r += "\n" + strings.Repeat(" ", i) + } + // If still not enough space then don't even try to wrap. + if wrap < 24 { + return s + } + + // Try to avoid short orphan words on the final line, by + // allowing wrapN to go a bit over if that would fit in the + // remainder of the line. + slop := 5 + wrap = wrap - slop + + // Handle first line, which is indented by the caller (or the + // special case above) + l, s = wrapN(wrap, slop, s) + r = r + l + + // Now wrap the rest + for s != "" { + var t string + + t, s = wrapN(wrap, slop, s) + r = r + "\n" + strings.Repeat(" ", i) + t + } + + return r + +} + +// FlagUsagesWrapped returns a string containing the usage information +// for all flags in the FlagSet. Wrapped to `cols` columns (0 for no +// wrapping) +func (f *FlagSet) FlagUsagesWrapped(cols int) string { x := new(bytes.Buffer) lines := make([]string, 0, len(f.formal)) @@ -546,12 +613,19 @@ func (f *FlagSet) FlagUsages() string { for _, line := range lines { sidx := strings.Index(line, "\x00") spacing := strings.Repeat(" ", maxlen-sidx) - fmt.Fprintln(x, line[:sidx], spacing, line[sidx+1:]) + // maxlen + 2 comes from + 1 for the \x00 and + 1 for the (deliberate) off-by-one in maxlen-sidx + fmt.Fprintln(x, line[:sidx], spacing, wrap(maxlen+2, cols, line[sidx+1:])) } return x.String() } +// FlagUsages returns a string containing the usage information for all flags in +// the FlagSet +func (f *FlagSet) FlagUsages() string { + return f.FlagUsagesWrapped(0) +} + // PrintDefaults prints to standard error the default values of all defined command-line flags. func PrintDefaults() { CommandLine.PrintDefaults() |