javascript - 如何使撤消和重做与我的文本同步解决方案配合使用？

Question

很少的东西。

首先，由于某种原因，粘贴所选文本在此站点中不起作用(当我在我的计算机上调试它时，它起作用) - 它始终提供对鼠标位置 0 和 0 的选择。

其次 - 除了重做和撤消之外，与文本的所有其他交互都必须正常。

我尝试实现一个缓冲区来存储它们之前的文本替换长度，因为您可能知道重做和撤消没有 ev.data 并且我需要知道我要替换的文本 - 这些事件会随着新文本以及之前的选择开始和选择结束而触发。

我已经用我自己的本地服务器替换了 post 请求，该服务器只是通过相同的“请求”修改了之前的“已收到”文本。

我正在尝试实现实时共享功能，以便每个参与者仅发送新旧文本之间的差异。

所以在大多数情况下，它目前工作正常，除了我不知道如何使重做和撤消工作。任何帮助将不胜感激。

const codeelem = document.getElementById("code")

//here server simulated

//normally the postcode will send the adjustments to the server

//and previoustext will be the copy in the server

//I'll wait on a socket to recieve the update and apply it

let previoustext = "";

const postcode = (startpos, endpos, input, incaseerrormsg) => previoustext = codeelem.value = previoustext.slice(0, startpos) +
input +
previoustext.slice(endpos)

//mouse selection startpos and endpos plus a flag and a handler
let startpos,
endpos,
mouseshenanigans = false,
mouseshenaniganshandler = function (ev) {
    // I actually don't know why am I checking if the start and end selection are equal here
    //before setting the flag
    // in any case it should not make a difference
    this.selectionStart != this.selectionEnd && (mouseshenanigans = true);
    (startpos = this.selectionStart), (endpos = codeelem.selectionEnd)
}

//detect if the mouse has selected a text

codeelem.addEventListener("select", mouseshenaniganshandler)

//or if the mouse has changed position in the text
//this is also reset on every input

codeelem.addEventListener("mouseup", function (ev) {
mouseshenanigans = false
})

//keep track of history

/** @type {[number, number, string][]} */
let historyredo = []
/** @type {Number} */
let currentredo = -1

//paste workaround so I don't need to prompt the user for
//copy and paste permission to see which is the new text copied
//I simply save last position before the paste

let lastselectionstart

document.addEventListener("paste", event => {
lastselectionstart = codeelem.selectionStart
})

codeelem.addEventListener("input", async function (ev) {

//if the mouse has selected text
//use that
const startopsinner = mouseshenanigans ? startpos : this.selectionStart,
    endposinner = mouseshenanigans ? endpos : this.selectionEnd


//detailed diagnostics
console.log('\n')
console.log({
    historyredolength: historyredo.length,
    currentredo
})
console.log('\n\n\n')
console.log({
    value: this.value,
    previoustext,
    eventtype: ev.inputType
})
console.log('\n'), console.log({
    mouseshenanigans,
    selectionStart: this.selectionStart,
    selectionEnd: this.selectionEnd,
    data: ev.data,
    datansliceselection: this.value.slice(this.selectionStart, this.selectionEnd),
})

mouseshenanigans && (console.log('\n'), console.log({
    startopsinner,
    endposinner,
    datasliceposinner: this.value.slice(startopsinner, endposinner)
}))

switch (ev.inputType) {
    //if deleting or inserting text
    case "deleteContentBackward":
    case "insertText":
        //if the last character and not deleting backwards
        if (this.value.slice(startopsinner, endposinner) == "" && ev.inputType != "deleteContentBackward")
            postcode(
                this.selectionStart,
                this.selectionEnd + 1,
                ev.data || "",
                "you have been violated"
            )
        //else depending if there is a mouse selction
        //use the start and end position of those
        //or else use the current selection
        //since the current selection is of the replaced already text
        else
            postcode(
                mouseshenanigans ? startpos : this.selectionStart,
                mouseshenanigans ? endpos : this.selectionEnd,
                ev.data || "",
                "you have been violated"
            )
        break
    //simillar situation for pasting text
    //except we don't have the paste
    //so we are using the last saved position from the paste event
    //to slice it from the replaced text
    case "insertFromPaste":
        postcode(
            mouseshenanigans ? startpos : lastselectionstart,
            mouseshenanigans ? endpos : lastselectionstart,
            this.value.slice(lastselectionstart, this.selectionEnd),
            "you have been violated"
        )
        break

    //now here I have no idea how to make this work
    case "historyRedo":
    case "historyUndo":
        console.log('\n')
        console.log({
            historyredo0: historyredo[currentredo][0],
            historyredo1: historyredo[currentredo][1],
            historyredo2: historyredo[currentredo][2]
        })
        if (this.selectionStart != this.selectionEnd)
            postcode(
                this.selectionStart,
                this.selectionStart + historyredo[currentredo][1],
                this.value.slice(
                    this.selectionStart,
                    this.selectionEnd
                ),
                "you have been violated"
            )
        //trying to save some of the previous data
        ev.inputType == "historyUndo" ? (historyredo.push([startopsinner, historyredo[currentredo][1], previoustext.slice(startopsinner, endposinner)]), ++currentredo) : (--currentredo, historyredo.pop())
        break
}
//trying to save some of the previous data
const isnotundoorredo = ev.inputType != "historyRedo" && ev.inputType != "historyUndo"
isnotundoorredo && (historyredo.push([startopsinner, ev.data.length, previoustext.slice(startopsinner, endposinner)]), ++currentredo)
//since we had typed no more mouse shenanigans
mouseshenanigans = false
})

<textarea id="code"></textarea>

Answer 1

开发文本编辑器的一种更直观的方法是使用 contenteditable非输入类型元素上的属性和 .execCommand()方法。

演示

const editor = document.forms.editor;
const exc = editor.elements;

exc.undo.onclick = function(e) { document.execCommand('undo', false, null) }

exc.redo.onclick = function(e) { document.execCommand('redo', false, null) }

:root, body {font: 400 3vw/1 Consolas}
#text {min-height: 20vh;word-wrap:wrap;word-break:break-word;padding: 5px;overflow:hidden;}
button {font-size: 2rem; line-height: 1;padding: 0;border:0;cursor:pointer}

<form id='editor'>
  <fieldset id='text' contenteditable></fieldset>
  <fieldset id='btns'>
    <button id='undo' type='button'>🔄</button>
    <button id='redo' type='button'>🔀</button>
  </fieldset>
</form>