[lazerg]

Summary:

processFilter read an omitted amount as 0. ARGS_WITH_UNITS_REGEX matches an empty string and Number('') is 0, so brightness() painted the view black and opacity() hid it. It also accepted px for brightness, contrast, grayscale, invert, opacity, saturate and sepia, so brightness(2px) was applied as brightness(2).

These seven functions now default an empty amount to 1 and reject px, which is what CSS Filter Effects says and what the native CSSFilter parser already does (see the brightness_default and bightness_length cases in CSSFilterTest.cpp). blur() and hue-rotate() already fell back to 0, which is their CSS default, so they don't change.

Fixes #59604

Changelog:

[GENERAL] [FIXED] - filter functions like brightness() with no amount now default to 1 instead of 0, and px amounts are rejected for them

Test Plan:

In processFilter-itest.js I changed the px case of testStandardFilter to expect no filters and added a () case that expects an amount of 1. I ran the file through plain Jest (without the Fantom environment import): 21 cases fail on main and all 116 pass with this change. Flow, ESLint and Prettier are clean. I didn't run the Fantom runner or the reproducer on a device.

[github-actions]

Visual regression

1 visual difference(s) at 86d4c7eba228. Visual differences need maintainer approval. Review the report, then apply visual-change-approved.

ios button/default-styling/default: Changed, 38223 px (1.533%)

Expected and Captured

Expected	Captured