fix viewport

[star-e]

Re: #

Changelog

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Continuous Integration

This pull request:

• needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

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Compatibility Check

This pull request:

• changes public API, and have ensured backward compatibility with deprecated features.
• affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• affects file structure of the build package or build configuration which requires user project upgrade.
• introduces breaking changes, please list all changes, affected features and the scope of violation.

Greptile Overview

Greptile Summary

This PR adds Math.ceil() to round up canvasSize.width and canvasSize.height at the end of _calculateLabelFont() method. This ensures that canvas dimensions are always integers rather than fractional values.

Key Changes:

• Added two lines in text-processing.ts:257-258 to ceil canvas dimensions after all overflow mode calculations complete
• Applied uniformly after all canvas size calculations (NONE, SHRINK, CLAMP, RESIZE_HEIGHT overflow modes)

Impact:
HTML Canvas elements require integer dimensions for proper rendering. Fractional pixel values from font calculations can cause viewport and rendering artifacts. This fix prevents such issues by ensuring dimensions are whole numbers before the canvas is used in _updateLabelDimensions().

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The change is simple, well-placed, and follows best practices for canvas dimension handling. Using Math.ceil() ensures dimensions are always valid integers without truncating content. The fix is applied after all size calculations, preserving existing logic while preventing fractional pixel issues. No breaking changes or side effects expected.
• No files require special attention

Important Files Changed

Filename	Overview
cocos/2d/assembler/label/text-processing.ts	Added Math.ceil() to ensure canvas dimensions are integers, preventing potential rendering issues from fractional pixel values

Sequence Diagram

sequenceDiagram
    participant Client as Label Component
    participant TP as TextProcessing
    participant Canvas as HTML Canvas
    
    Client->>TP: processingString()
    TP->>TP: _calculateLabelFont()
    Note over TP: Calculate canvasSize based on<br/>overflow mode (NONE, SHRINK, etc.)
    TP->>TP: Math.ceil(canvasSize.width)
    TP->>TP: Math.ceil(canvasSize.height)
    Note over TP: NEW: Ensure integer dimensions<br/>to fix viewport issues
    
    Client->>TP: generateRenderInfo()
    TP->>TP: _updateLabelDimensions()
    TP->>Canvas: canvas.width = canvasSize.width
    TP->>Canvas: canvas.height = canvasSize.height
    Note over Canvas: Canvas dimensions must be integers<br/>Fractional values can cause rendering issues

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Code Size Check Report

Wechat (WASM)	Before	After	Diff
2D Empty (legacy pipeline)	1001979 bytes	1001979 bytes	✅ 0 bytes
2D All (legacy pipeline)	2662998 bytes	2662998 bytes	✅ 0 bytes
2D All (new pipeline)	2750227 bytes	2750227 bytes	✅ 0 bytes
(2D + 3D) All	10003609 bytes	10003609 bytes	✅ 0 bytes

Web (WASM + ASMJS)	Before	After	Diff
(2D + 3D) All	16915881 bytes	16915881 bytes	✅ 0 bytes

Interface Check Report

This pull request does not change any public interfaces !