Since check/uncheck does click under the hood, sometimes it might
need to click at a different position. One example would be a long
label that contains links inside, and clicking in the center happens
to hit the link instead of the label itself.
- Instead of capturing snapshots on demand, we now stream them
from each frame every 100ms.
- Certain actions can also force snapshots at particular moment using
"checkpoints".
- Trace viewer is able to show the page snapshot at a particular
timestamp, or using a "checkpoint" snapshot.
- Small optimization to not process stylesheets if CSSOM was not used.
There still is a lot of room for improvement.
This adds `{Page,Frame}.isChecked(selector)` and `ElementHandle.isChecked()` methods.
Useful to do assertions in tests:
```js
await page.click('text="Add TODO"');
expect(await page.isChecked('.item-done')).toBe(false);
```
These methods are useful for verification in tests, e.g.
```js
expect(await page.isEnabled(':text("Remove All")')).toBe(false);
await page.click(':text("Add Item")');
expect(await page.isVisible('.item:text("new item")')).toBe(true);
expect(await page.isEnabled(':text("Remove All")')).toBe(true);
```
When element with position:sticky covers some part of
the scroll container, we could fail to scroll from under it
to perform an action. To fight this, we can try different
scroll alignments and scroll to the top/bottom/center
in the attempt to scroll away from sticky header/footer/sidebar.
This saves some CPU cycles while waiting for the page to
change the state, e.g. for animations to complete.
Note that retrying logic is only applicable in rare
circumstances like unexpected scroll in the middle of an
action, or some overlay blocking the click. Usually,
action times out in this cases while retrying.
- Fill and click actions pass metadata to Progress.
- Progress reports success/failure through instrumentation.
- Tracer consumes ActionResult and ActionMetadata and records them.
Currently, only click and fill actions pass metadata to
contain the size of the change. Everything else should follow.
This is a large rework of selectors:
- Each BrowserContext now has a separate Selectors instance that has its own registrations.
Most of them share a single sharedSelectors instance, but contexts created for a connected
browser have their own instance.
- Connected browser now gets a RemoteBrowser object that encapsulates Selectors and Browser.
This Selectors object is registered with the api selectors.
- Public selectors.register api iterates over all registered Selectors channels
and registers in each of them.
- createSelector testing method migrated to ElementHandle._createSelectorForTest.
