add context menu to inputs

closes #1217

public/contextMenu.js

@@ -0,0 +1,30 @@
+const { Menu } = require('electron');
+
+// https://github.com/electron/electron/issues/4068#issuecomment-274159726
+module.exports = (window) => {
+  const selectionMenu = Menu.buildFromTemplate([
+    { role: 'copy' },
+    { type: 'separator' },
+    { role: 'selectall' },
+  ]);
+
+  const inputMenu = Menu.buildFromTemplate([
+    { role: 'undo' },
+    { role: 'redo' },
+    { type: 'separator' },
+    { role: 'cut' },
+    { role: 'copy' },
+    { role: 'paste' },
+    { type: 'separator' },
+    { role: 'selectall' },
+  ]);
+
+  window.webContents.on('context-menu', (e, props) => {
+    const { selectionText, isEditable } = props;
+    if (isEditable) {
+      inputMenu.popup(window);
+    } else if (selectionText && selectionText.trim() !== '') {
+      selectionMenu.popup(window);
+    }
+  });
+};

public/electron.js

@@ -16,6 +16,7 @@ const logger = require('./logger');
 const menu = require('./menu');
 const configStore = require('./configStore');
 const { frontendBuildDir } = require('./util');
+const attachContextMenu = require('./contextMenu');
 
 const { checkNewVersion } = require('./update-checker');
 
@@ -108,6 +109,8 @@ function createWindow() {
 
   remote.enable(mainWindow.webContents);
 
+  attachContextMenu(mainWindow);
+
 
   if (isDev) mainWindow.loadURL('http://localhost:3001');
   // Need to useloadFile for special characters https://github.com/mifi/lossless-cut/issues/40