This patch implements a new image comparison function, codenamed
"ssim-cie94". The goal of the new comparison function is to cancel out
browser non-determenistic rendering.
To use the new comparison function:
```ts
await expect(page).toHaveScreenshot({
comparator: 'ssim-cie94',
});
```
As of Nov 30, 2022, we identified the following sources of
non-determenistic rendering for Chromium:
- Anti-aliasing for certain shapes might be different due to the
way skia rasterizes certain shapes.
- Color blending might be different on `x86` and `aarch64`
architectures.
The new function employs a few heuristics to fight these
differences.
Consider two non-equal image pixels `(r1, g1, b1)` and `(r2, g2, b2)`:
1. If the [CIE94] metric is less then 1.0, then we consider these pixels
**EQUAL**. (The value `1.0` is the [just-noticeable difference] for
[CIE94].). Otherwise, proceed to next step.
1. If all the 8 neighbors of the first pixel match its color, or
if the 8 neighbors of the second pixel match its color, then these
pixels are **DIFFERENT**. (In case of anti-aliasing, some of the
direct neighbors have to be blended up or down.) Otherwise, proceed
to next step.
1. If SSIM in some locality around the different pixels is more than
0.99, then consider this pixels to be **EQUAL**. Otherwise, mark them
as **DIFFERENT**. (Local SSIM for anti-aliased pixels turns out to be
very close to 1.0).
[CIE94]: https://en.wikipedia.org/wiki/Color_difference#CIE94
[just-noticeable difference]:
https://en.wikipedia.org/wiki/Just-noticeable_difference
Following the `getByText()` and other methods:
- By default, matching is substring and case-insensitive. Before, it was
only case-insensitive, but not substring.
- With new option `exact: true`, matching is full string and
case-sensitive.
- Matching always normalizes whitespace.
- Codegen generates `exact: false` by default.
- `internal:role` treats `[name="foo"i]` as non-exact match.
Various fixes:
- Updated `getByRole` docs to match the reality.
- Locator generator edge cases.
- Rename internal selectors `has`, `control` and `attr` to
`internal:has`, `internal:control` and `internal:attr`.
- Fix `getByLabel()` to respect strictness, by introducing
`internal:label` selector.
- Move tests essential for ports to `selectors-by.spec`.
This makes `HttpServer` accept `preferredPort` option that will first
try to listen on that port, and if that port is already in use, listen
on some available port instead.
Fixes#17201.
Resolves#14255.
PNGs should be preferred as they are deterministic, but increasing this
limit should be fine for JPEG users. (Looking through jpeg-js source code, the actual memory allocation is based on the size of the image—so unless a user is hitting this limit already—this should not impact the memory consumption of Playwright.
This allows us to use the full retry logic of rimraf in the `onexit` handler.
Note this is already covered by failing on Windows test
`should remove temp dir on process.exit`.
