Implementation of Viewport Zoom Check

https://www.w3.org/WAI/standards-guidelines/act/rules/b4f0c3

Summary

A comprehensive improvement has been implemented for reflow suite, including checking that the meta viewport allows zooming up to 200%.

New Feature Implemented

1. Test Step IsZoomeable

Location: src/a11y_test_definitions/test_step/common.py

Feature:

• Verifies that the meta viewport does not prevent zooming up to 200%
• Implements the "Meta viewport allows for zoom" rule
• Runs before reflow tests to detect early restrictions

Cases that PASS:

<meta name="viewport" content="user-scalable=yes" />
<meta name="viewport" content="maximum-scale=2.0" />
<meta name="viewport" content="maximum-scale=-1" />
<meta name="viewport" content="width=device-width" />

Cases that FAIL:

<meta name="viewport" content="user-scalable=no" />
<meta name="viewport" content="maximum-scale=1.5" />
<meta name="viewport" content="maximum-scale=1.0" />
<meta name="viewport" content="maximum-scale=yes" />

INAPPLICABLE Cases:

• No meta viewport
• Meta viewport without content attribute
• Empty content or without zoom properties

4. Complete Unit Tests

Location: tests/test_is_zoomeable.py

Coverage:

• All PASS cases of the ACT rule
• All FAIL cases of the ACT rule
• All INAPPLICABLE cases of the ACT rule
• Cases edge: multiple metas, case-insensitive, whitespace
• Error and exception handling
• Unit tests for helper methods

Implementation Benefits

• Verifies that text and content can be resized up to 200%
• Detects viewport restrictions that would prevent zooming
• Complements content loss tests
• Identifies viewport issues before the zoom test
• Avoids false negatives in reflow tests
• Provides specific feedback on restrictions
• Can have its own report