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line_style.go
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line_style.go
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// Copyright 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package draw
import (
"fmt"
"github.com/mum4k/termdash/internal/runewidth"
"github.com/mum4k/termdash/linestyle"
)
// line_style.go contains the Unicode characters used for drawing lines of
// different styles.
// lineStyleChars maps the line styles to the corresponding component characters.
// Source: http://en.wikipedia.org/wiki/Box-drawing_character.
var lineStyleChars = map[linestyle.LineStyle]map[linePart]rune{
linestyle.Light: {
hLine: '─',
vLine: '│',
topLeftCorner: '┌',
topRightCorner: '┐',
bottomLeftCorner: '└',
bottomRightCorner: '┘',
hAndUp: '┴',
hAndDown: '┬',
vAndLeft: '┤',
vAndRight: '├',
vAndH: '┼',
},
linestyle.Double: {
hLine: '═',
vLine: '║',
topLeftCorner: '╔',
topRightCorner: '╗',
bottomLeftCorner: '╚',
bottomRightCorner: '╝',
hAndUp: '╩',
hAndDown: '╦',
vAndLeft: '╣',
vAndRight: '╠',
vAndH: '╬',
},
linestyle.Round: {
hLine: '─',
vLine: '│',
topLeftCorner: '╭',
topRightCorner: '╮',
bottomLeftCorner: '╰',
bottomRightCorner: '╯',
hAndUp: '┴',
hAndDown: '┬',
vAndLeft: '┤',
vAndRight: '├',
vAndH: '┼',
},
}
// init verifies that all line parts are half-width runes (occupy only one
// cell).
func init() {
for ls, parts := range lineStyleChars {
for part, r := range parts {
if got := runewidth.RuneWidth(r); got > 1 {
panic(fmt.Errorf("line style %v line part %v is a rune %c with width %v, all parts must be half-width runes (width of one)", ls, part, r, got))
}
}
}
}
// lineParts returns the line component characters for the provided line style.
func lineParts(ls linestyle.LineStyle) (map[linePart]rune, error) {
parts, ok := lineStyleChars[ls]
if !ok {
return nil, fmt.Errorf("unsupported line style %d", ls)
}
return parts, nil
}
// linePart identifies individual line parts.
type linePart int
// String implements fmt.Stringer()
func (lp linePart) String() string {
if n, ok := linePartNames[lp]; ok {
return n
}
return "linePartUnknown"
}
// linePartNames maps linePart values to human readable names.
var linePartNames = map[linePart]string{
vLine: "linePartVLine",
topLeftCorner: "linePartTopLeftCorner",
topRightCorner: "linePartTopRightCorner",
bottomLeftCorner: "linePartBottomLeftCorner",
bottomRightCorner: "linePartBottomRightCorner",
hAndUp: "linePartHAndUp",
hAndDown: "linePartHAndDown",
vAndLeft: "linePartVAndLeft",
vAndRight: "linePartVAndRight",
vAndH: "linePartVAndH",
}
const (
hLine linePart = iota
vLine
topLeftCorner
topRightCorner
bottomLeftCorner
bottomRightCorner
hAndUp
hAndDown
vAndLeft
vAndRight
vAndH
)