main.js

const { app, BrowserWindow, ipcMain } = require("electron");

function createWindow() {
  let win = new BrowserWindow({
    frame: false,
    alwaysOnTop: true,
    transparent: true,
    skipTaskbar: true,
    opacity: 0.8,
    webPreferences: {
      nodeIntegration: true,
      contextIsolation: false,
    },
  });

  win.loadFile("index.html");

  ipcMain.on(
    "resize",
    function (e, targetSizeX, targetSizeY, anchorRight, anchorBottom) {
      if (anchorRight == true || anchorBottom == true) {
        var targetPosX;
        var targetPosY;
        var [originalPosX, originalPosY] = win.getPosition();
        var [originalSizeX, originalSizeY] = win.getSize();

        if (anchorRight == true) {
          targetPosX = originalPosX + (originalSizeX - targetSizeX);
        } else {
          targetPosX = originalPosX;
        }

        if (anchorBottom == true) {
          targetPosY = originalPosY + (originalSizeY - targetSizeY);
        } else {
          targetPosY = originalPosY;
        }
        win.setPosition(targetPosX, targetPosY);
      }

      win.setContentSize(targetSizeX, targetSizeY);
    }
  );

  ipcMain.on("quit", function () {
    app.quit();
  });

  // Open dev tools in separate window.
  // win.webContents.openDevTools({mode:'undocked'});
}

app.on("ready", createWindow);