chromium/src/third_party/blink/web_tests/virtual/threaded/synthetic_gestures/synthetic-pinch-zoom-gesture.js

const kScaleEpsilon = 0.1;
const kOffsetEpsilon = 2;

const centerX = window.innerWidth / 2;
const centerY = window.innerHeight / 2;

// TODO(bokan): Add more variations (speed, anchor location, etc.) but it's
// difficult right now as pinchBy is badly broken on desktops:
// https://crbug.com/787615.
// TODO(bokan): |ignore_offset| is added temporarily to allow testing the
// pinch-zoom on desktop in a less strict way. Currently, touchscreen pinch-zoom
// on desktop doesn't zoom to the expected location. Until that's fixed we'll
// run tests without checking the location so we guard regressing the scale but
// once it's fixed we can remove this and run the strict tests.
// https://crbug.com/787615
function runTest(t, testCase, ignore_offset) {
  return new Promise(t.step_func((resolve, reject) => {
    internals.setPageScaleFactor(testCase.startingScale);
    internals.setVisualViewportOffset(
        window.innerWidth * (1 - (1 / testCase.startingScale)) / 2,
        window.innerHeight * (1 - (1 / testCase.startingScale)) / 2);

    // Ensure the compositor knows the starting scale and offset.
    waitForCompositorCommit().then(t.step_func(() => {
      chrome.gpuBenchmarking.pinchBy(
          testCase.scale, centerX, centerY, t.step_func(() => {
            waitForCompositorCommit().then(t.step_func(() => {
              const expectedScale = testCase.startingScale * testCase.scale;
              assert_approx_equals(
                  window.visualViewport.scale, expectedScale, kScaleEpsilon,
                  testCase.msg + ' has correct page scale factor.');
              if (!ignore_offset) {
                assert_approx_equals(
                    window.visualViewport.offsetLeft,
                    window.innerWidth * (1 - (1 / expectedScale)) / 2,
                    kOffsetEpsilon,
                    testCase.msg + ' has correct visual viewport offsetLeft.');
                assert_approx_equals(
                    window.visualViewport.offsetTop,
                    window.innerHeight * (1 - (1 / expectedScale)) / 2,
                    kOffsetEpsilon,
                    testCase.msg + ' has correct visual viewport offsetTop.');
              }
              resolve();
            }));
          }),
          testCase.speed, testCase.gestureSource);
    }));
  }));
}

async function runAllTestCases(t, testCases) {
  for (const testCase of testCases) {
    await runTest(t, testCase, false);
  }
}

async function runAllTestCasesDesktop(t, testCases) {
  for (const testCase of testCases) {
    await runTest(t, testCase, true);
  }
}