gecko-dev/browser/base/content/test/general/browser_printpreview.js

function test() {
  waitForExplicitFinish();

  ok(!gInPrintPreviewMode,
     "Should NOT be in print preview mode at starting this tests");
  // Skip access key test on platforms which don't support access key.
  if (!/Win|Linux/.test(navigator.platform)) {
    openPrintPreview(testClosePrintPreviewWithEscKey);
  } else {
    openPrintPreview(testClosePrintPreviewWithAccessKey);
  }
}

function testClosePrintPreviewWithAccessKey() {
  EventUtils.synthesizeKey("c", { altKey: true });
  checkPrintPreviewClosed(function (aSucceeded) {
    ok(aSucceeded,
       "print preview mode should be finished by access key");
    openPrintPreview(testClosePrintPreviewWithEscKey);
  });
}

function testClosePrintPreviewWithEscKey() {
  EventUtils.synthesizeKey("VK_ESCAPE", {});
  checkPrintPreviewClosed(function (aSucceeded) {
    ok(aSucceeded,
       "print preview mode should be finished by Esc key press");
    openPrintPreview(testClosePrintPreviewWithClosingWindowShortcutKey);
  });
}

function testClosePrintPreviewWithClosingWindowShortcutKey() {
  EventUtils.synthesizeKey("w", { accelKey: true });
  checkPrintPreviewClosed(function (aSucceeded) {
    ok(aSucceeded,
       "print preview mode should be finished by closing window shortcut key");
    finish();
  });
}

function openPrintPreview(aCallback) {
  document.getElementById("cmd_printPreview").doCommand();
  executeSoon(function () {
    if (gInPrintPreviewMode) {
      executeSoon(aCallback);
      return;
    }
    executeSoon(arguments.callee);
  });
}

function checkPrintPreviewClosed(aCallback) {
  let count = 0;
  executeSoon(function () {
    if (!gInPrintPreviewMode) {
      executeSoon(function () { aCallback(count < 1000); });
      return;
    }
    if (++count == 1000) {
      // The test might fail.
      PrintUtils.exitPrintPreview();
    }
    executeSoon(arguments.callee);
  });
}