ergonomy.gesture without touch action

ergonomy.gesture-without-touch-action

Rule ID: ergonomy.gesture-without-touch-action Severity: WARN Category: ergonomy Target Standards: W3C Pointer Events Level 3 Section 5.2.8 (The touch-action CSS Property), Chromium & WebKit Compositor Gesture Isolation Architecture, Google Chrome Developers (Touch Action Best Practices)

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1. Overview & Core Invariant

Enforces CSS touch-action declaration on elements with custom gesture swipe/drag event handlers

Core Invariant:

"Elements attaching custom swipe or drag listeners ('onTouchMove', 'onPointerMove') must declare explicit CSS 'touch-action' ('touch-pan-y', 'touch-none') to prevent gesture cancellation by native scrolling."

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2. Technical Grounding & Engine Realities

When users drag or swipe an element, the browser mobile compositor thread must determine whether to handle native scrolling or yield control to JavaScript.

Without explicit CSS 'touch-action' (e.g. 'touch-pan-y' for horizontal sliders or 'touch-none' for drawing canvases), browser vertical scrolling immediately cancels the custom touch gesture mid-drag, causing abrupt freezing or unwanted page scrolling.

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3. Vulnerability & Risk Taxonomy

Risk Vector	Severity	Impact
Abrupt Gesture Cancellation	MEDIUM	Swipeable cards and carousels stutter or lock up mid-swipe when the mobile browser takes over scrolling.
Accidental Page Scrolling	MEDIUM	Users attempting to pan a map or slider accidentally scroll the entire page off-screen.

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4. Non-Compliant Code Patterns (Bad Examples)

TSX (Horizontal swipeable container without touch-action):

<div
  onTouchStart={handleStart}
  onTouchMove={handleMove}
  className="flex overflow-x-auto gap-4 p-4"
>
  <div className="w-64 h-40 bg-card rounded-2xl shrink-0">Kartu 1</div>
</div>

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5. Compliant Implementation Patterns (Good Examples)

TSX (Explicit touch-pan-y coordinates compositor axis smoothly):

<div
  onTouchStart={handleStart}
  onTouchMove={handleMove}
  className="flex overflow-x-auto gap-4 p-4 touch-pan-y"
>
  <div className="w-64 h-40 bg-card rounded-2xl shrink-0">Kartu 1</div>
</div>

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6. Detection & Verification Pipeline (How The Rule Evaluates Code)

This rule evaluates source code through the standard AST inspection pipeline:

flowchart TD
    Node["AST Node (Astro / TSX element)"] --> Inspect["1. Inspect Element & Attributes"]
    Inspect --> Invariant{"2. Evaluate Rule Invariant"}
    Invariant -- "Compliant" --> Safe["Pass"]
    Invariant -- "Non-Compliant" --> IgnoreCheck{"3. Check charites:ignore directive"}
    IgnoreCheck -- "Ignored" --> Safe
    IgnoreCheck -- "Not Ignored" --> Diag["4. Emit Diagnostic: ergonomy.gesture-without-touch-action"]

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Step-by-Step Evaluation:

1. AST Traversal: Visits normalized ir.Node structures during AST streaming.
2. Invariant Check: Compares node attributes against rule invariants.
3. Directive Suppression Check: Honors inline charites:ignore ergonomy.gesture-without-touch-action directives.
4. Diagnostic Emission: Emits compiler-grade diagnostic on invariant violation.

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7. Verification & Test Harness (How The Test Works: 1-SSOT Tri-Corpus)

This rule is rigorously tested and validated across the canonical 1-SSOT Tri-Corpus in tests/correctness/ergonomy.gesture-without-touch-action/:

flowchart TD
    subgraph GoldenCorpus ["1-SSOT Tri-Corpus Test Matrix for ergonomy.gesture-without-touch-action"]
        subgraph P ["Positive Corpus (tests/correctness/ergonomy.gesture-without-touch-action/positive/)"]
            P1["P1: Obvious Direct Violation"]
            P2["P2: Indirect / Variant Concatenation"]
            P3["P3: Helper / clsx / cn Wrapper"]
            P4["P4: Deeply Nested Elements"]
            P5["P5: Aliased Imports / Re-exports"]
        end
        subgraph N ["Negative Corpus (tests/correctness/ergonomy.gesture-without-touch-action/negative/)"]
            N1["N1: Valid Design Tokens"]
            N2["N2: Explicit charites:ignore Directive"]
            N3["N3: Third-Party / Vendor Components"]
            N4["N4: Clean Semantic HTML"]
            N5["N5: Untokenized Custom Values (Banana Test)"]
        end
        subgraph A ["Adversarial Corpus (tests/correctness/ergonomy.gesture-without-touch-action/adversarial/)"]
            A1["A1: Template Literal Interpolations"]
            A2["A2: Ternary Conditional Expressions"]
            A3["A3: Spread Properties & Dynamic Overrides"]
            A4["A4: Dynamic Object Class Syntax"]
            A5["A5: Shadowed Variable Identifiers"]
            A6["A6: Nested Closures & HOC Wrappers"]
            A7["A7: Obfuscated Classes & Cyclic Tokens"]
        end
    end

    P --> TestRunner["Automated Runner (rule_test.go)"]
    N --> TestRunner
    A --> TestRunner
    TestRunner --> Gates["Quality Gates: Zero Panic, Zero False-Positive, Zero Bypass"]

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• Positive Fixtures (P1-P5): Verified to trigger diagnostics at exact lines and column spans.
• Negative Fixtures (N1-N5): Verified to produce zero diagnostics on valid tokens and legitimate exemptions.
• Adversarial Fixtures (A1-A7): Verified to prevent evasion across dynamic expressions, string interpolations, and cyclic references.

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8. How to Suppress (Ignore Directives)

If this pattern is required for an intentional exception, suppress the diagnostic using the canonical Charites Rule ID:

<!-- charites:ignore ergonomy.gesture-without-touch-action intentional exception -->

// charites:ignore ergonomy.gesture-without-touch-action intentional exception

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9. Configuration Reference (charites.yaml)

rules:
  ergonomy.gesture-without-touch-action:
    severity: warn # error | warn | info | off