mirror of https://github.com/mum4k/termdash.git
118 lines
3.4 KiB
Go
118 lines
3.4 KiB
Go
// Copyright 2018 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 text
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import (
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"fmt"
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"image"
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"github.com/mum4k/termdash/internal/canvas"
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"github.com/mum4k/termdash/internal/runewidth"
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"github.com/mum4k/termdash/internal/wrap"
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)
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// line_trim.go contains code that trims lines that are too long.
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type trimResult struct {
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// trimmed is set to true if the current and the following runes on this
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// line are trimmed.
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trimmed bool
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// curPoint is the updated current point the drawing should continue on.
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curPoint image.Point
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}
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// drawTrimChar draws the horizontal ellipsis '…' character as the last
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// character in the canvas on the specified line.
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func drawTrimChar(cvs *canvas.Canvas, line int) error {
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lastPoint := image.Point{cvs.Area().Dx() - 1, line}
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// If the penultimate cell contains a full-width rune, we need to clear it
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// first. Otherwise the trim char would cover just half of it.
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if width := cvs.Area().Dx(); width > 1 {
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penUlt := image.Point{width - 2, line}
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prev, err := cvs.Cell(penUlt)
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if err != nil {
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return err
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}
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if runewidth.RuneWidth(prev.Rune) == 2 {
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if _, err := cvs.SetCell(penUlt, 0); err != nil {
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return err
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}
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}
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}
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cells, err := cvs.SetCell(lastPoint, '…')
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if err != nil {
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return err
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}
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if cells != 1 {
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panic(fmt.Errorf("invalid trim character, it occupies %d cells, the implementation only supports scroll markers that occupy exactly one cell", cells))
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}
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return nil
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}
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// lineTrim determines if the current line needs to be trimmed. The cvs is the
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// canvas assigned to the widget, the curPoint is the current point the widget
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// is going to place the curRune at. If line trimming is needed, this function
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// replaces the last character with the horizontal ellipsis '…' character.
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func lineTrim(cvs *canvas.Canvas, curPoint image.Point, curRune rune, opts *options) (*trimResult, error) {
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if opts.wrapMode == wrap.AtRunes {
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// Don't trim if the widget is configured to wrap lines.
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return &trimResult{
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trimmed: false,
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curPoint: curPoint,
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}, nil
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}
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// Newline characters are never trimmed, they start the next line.
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if curRune == '\n' {
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return &trimResult{
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trimmed: false,
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curPoint: curPoint,
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}, nil
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}
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width := cvs.Area().Dx()
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rw := runewidth.RuneWidth(curRune)
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switch {
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case rw == 1:
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if curPoint.X == width {
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if err := drawTrimChar(cvs, curPoint.Y); err != nil {
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return nil, err
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}
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}
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case rw == 2:
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if curPoint.X == width || curPoint.X == width-1 {
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if err := drawTrimChar(cvs, curPoint.Y); err != nil {
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return nil, err
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}
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}
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default:
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return nil, fmt.Errorf("unable to decide line trimming at position %v for rune %q which has an unsupported width %d", curPoint, curRune, rw)
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}
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trimmed := curPoint.X > width-rw
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if trimmed {
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curPoint = image.Point{curPoint.X + rw, curPoint.Y}
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}
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return &trimResult{
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trimmed: trimmed,
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curPoint: curPoint,
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}, nil
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}
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