mirror of https://github.com/mum4k/termdash.git
99 lines
2.7 KiB
Go
99 lines
2.7 KiB
Go
// Copyright 2019 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package runewidth is a wrapper over github.com/mattn/go-runewidth which
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// gives different treatment to certain runes with ambiguous width.
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package runewidth
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import runewidth "github.com/mattn/go-runewidth"
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// RuneWidth returns the number of cells needed to draw r.
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// Background in http://www.unicode.org/reports/tr11/.
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//
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// Treats runes used internally by termdash as single-cell (half-width) runes
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// regardless of the locale. I.e. runes that are used to draw lines, boxes,
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// indicate resize or text trimming was needed and runes used by the braille
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// canvas.
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//
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// This should be safe, since even in locales where these runes have ambiguous
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// width, we still place all the character content around them so they should
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// have be half-width.
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func RuneWidth(r rune) int {
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if inTable(r, exceptions) {
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return 1
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}
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return runewidth.RuneWidth(r)
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}
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// StringWidth is like RuneWidth, but returns the number of cells occupied by
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// all the runes in the string.
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func StringWidth(s string) int {
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var width int
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for _, r := range []rune(s) {
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width += RuneWidth(r)
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}
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return width
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}
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// inTable determines if the rune falls within the table.
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// Copied from github.com/mattn/go-runewidth/blob/master/runewidth.go.
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func inTable(r rune, t table) bool {
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// func (t table) IncludesRune(r rune) bool {
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if r < t[0].first {
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return false
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}
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bot := 0
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top := len(t) - 1
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for top >= bot {
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mid := (bot + top) >> 1
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switch {
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case t[mid].last < r:
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bot = mid + 1
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case t[mid].first > r:
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top = mid - 1
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default:
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return true
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}
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}
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return false
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}
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type interval struct {
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first rune
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last rune
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}
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type table []interval
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// exceptions runes defined here are always considered to be half-width even if
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// they might be ambiguous in some contexts.
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var exceptions = table{
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// Characters used by termdash to indicate text trim or scroll.
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{0x2026, 0x2026},
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{0x21c4, 0x21c4},
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{0x21e7, 0x21e7},
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{0x21e9, 0x21e9},
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// Box drawing, used as line-styles.
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// https://en.wikipedia.org/wiki/Box-drawing_character
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{0x2500, 0x257F},
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// Block elements used as sparks.
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// https://en.wikipedia.org/wiki/Box-drawing_character
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{0x2580, 0x258F},
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}
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