javascript - How to print a DIV in ElectronJS

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javascript - How to print a DIV in ElectronJS

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

i'm trying to convert my web into an app made in ElectronJS

in my web i print a div with a barcode. this works pretty fine, but in electronjs i can't reach this.

originally i'd use this function

$scope.printDiv = function (divName) {
    var printContents = document.getElementById(divName).innerHTML;
    var popupWin = window.open('', '_blank', 'width=500,height=500');
    popupWin.document.open();
    popupWin.document.write('<html><head><link rel="stylesheet" type="text/css" href="styles/main.css"  type="text/css" media="print" /></head><body onload="window.print()">' + printContents + '</body></html>');
    popupWin.document.close();
}

with electronjs

i don't know how to pass the object to print.

also i'm trying to generate a PDF from content that i can load. but the PDF's are corrupted

var windowPrint = require('electron').remote.BrowserWindow;
    var fs = require('fs');
    var newWindow = new windowPrint({width: 800, height: 600, show: false});
    console.log(newWindow);
    newWindow.loadURL('http://github.com');
    newWindow.show();
    newWindow.webContents.print({silent: true, printBackground: true});
    newWindow.webContents.printToPDF({printSelectionOnly : true, printBackground: true}, function (error, data) {
        if (error) {
            throw error;
        }
        console.log(error);
        console.log(data);
        fs.writeFile('print.pdf', function (data, error) {
            if (error) {
                throw error;
            }
            console.log(error);
            console.log(data);
        });
    });

there's a simple way to print a DIV with electronjs?

thank you for reading.

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1 Answer

深蓝 · Answer 1 · 2021-10-23T17:46:41+0000

You have printed this page before loading is finished.

My approach: 1. create a mainwindow and a (invisible) worker window

import {app, BrowserWindow, Menu, ipcMain, shell} from "electron";
const os = require("os");
const fs = require("fs");
const path = require("path");

let mainWindow: Electron.BrowserWindow = undefined;
let workerWindow: Electron.BrowserWindow = undefined;

async function createWindow() {

    mainWindow = new BrowserWindow();
    mainWindow.loadURL("file://" + __dirname + "/index.html");
    mainWindow.webContents.openDevTools();
    mainWindow.on("closed", () => {
        // close worker windows later
        mainWindow = undefined;
    });

    workerWindow = new BrowserWindow();
    workerWindow.loadURL("file://" + __dirname + "/worker.html");
    // workerWindow.hide();
    workerWindow.webContents.openDevTools();
    workerWindow.on("closed", () => {
        workerWindow = undefined;
    });
}

// retransmit it to workerWindow
ipcMain.on("printPDF", (event: any, content: any) => {
    console.log(content);
    workerWindow.webContents.send("printPDF", content);
});
// when worker window is ready
ipcMain.on("readyToPrintPDF", (event) => {
    const pdfPath = path.join(os.tmpdir(), 'print.pdf');
    // Use default printing options
    workerWindow.webContents.printToPDF({}).then((data) {
        fs.writeFile(pdfPath, data, function (error) {
            if (error) {
                throw error
            }
            shell.openItem(pdfPath)
            event.sender.send('wrote-pdf', pdfPath)
        })
    }).catch((error) => {
       throw error;
    })
});

2, mainWindow.html

<head>
</head>
<body>
    <button id="btn"> Save </button>
    <script>
        const ipcRenderer = require("electron").ipcRenderer;

        // cannot send message to other windows directly https://github.com/electron/electron/issues/991
        function sendCommandToWorker(content) {
            ipcRenderer.send("printPDF", content);
        }

        document.getElementById("btn").addEventListener("click", () => {
            // send whatever you like
            sendCommandToWorker("<h1> hello </h1>");
        });
    </script>
</body>

3, worker.html

<head> </head>
<body>
    <script>
        const ipcRenderer = require("electron").ipcRenderer;

        ipcRenderer.on("printPDF", (event, content) => {
            document.body.innerHTML = content;

            ipcRenderer.send("readyToPrintPDF");
        });
    </script>
</body>

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