bianhaifeng789-hue/skills-experimental/decstbm-scroll-optimization

DECSTBM Scroll Optimization Skill

DECSTBM Scroll Optimization - ScrollHint type + DECSTBM scroll region + hardware scroll (SU/SD) + top/bottom rows + delta direction + scrollTop change detection + CSI n S/CSI n T pattern。

功能概述

从Claude Code的ink/render-node-to-output.ts提取的DECSTBM滚动优化模式，用于OpenClaw的终端滚动性能优化。

核心机制

ScrollHint Type

// DECSTBM scroll optimization hint. When a ScrollBox's scrollTop changes
// between frames (and nothing else moved), log-update.ts can emit a
// hardware scroll (DECSTBM + SU/SD) instead of rewriting the whole viewport.
export type ScrollHint = {
  top: number      // 0-indexed inclusive screen row
  bottom: number   // 0-indexed inclusive screen row
  delta: number    // >0: content moved up (scrollTop increased, CSI n S)
}
// Hardware scroll optimization
// Only scrollTop changed, nothing else moved
# DECSTBM + SU/SD CSI sequences

DECSTBM Scroll Region

// DECSTBM: Set Top and Bottom Margins
// CSI top ; bottom r
// Defines scroll region
// Only rows in region scroll
// Terminal scroll region
// Limits scroll area
# Efficient partial scroll

SU/SD CSI Sequences

// CSI n S: Scroll Down (content moves up, scrollTop increased)
// CSI n T: Scroll Up (content moves down, scrollTop decreased)
// Hardware scroll: terminal shifts rows
// No re-render needed
// Hardware scroll sequences
// CSI n S/CSI n T
# Skip full viewport rewrite

scrollTop Change Detection

// When a ScrollBox's scrollTop changes between frames
// (and nothing else moved), emit hardware scroll
// scrollTop diff only
// No layout shift
# Hardware scroll eligible

top/bottom Inclusive

// top/bottom are 0-indexed inclusive screen rows
// Define scroll region boundaries
// 0-indexed inclusive
// Region rows

delta Direction

// delta > 0: content moved up (scrollTop increased)
// CSI n S (scroll down n lines)
// delta < 0: content moved down (scrollTop decreased)
// CSI n T (scroll up n lines)
// Direction from delta
// CSI sequence choice

Reset Pattern

export function resetScrollHint(): void {
  scrollHint = null
  absoluteRectsPrev = absoluteRectsCur
  absoluteRectsCur = []
}
// Reset per-frame
// Record absolute rects
# Previous frame rects preserved

实现建议

OpenClaw适配

1. scrollHintType: ScrollHint type definition
2. decstbmScroll: DECSTBM scroll region pattern
3. csiSuSd: CSI n S/CSI n T sequences
4. scrollTopChange: scrollTop change detection
5. inclusiveRows: top/bottom inclusive rows

状态文件示例

{
  "scrollHint": {
    "top": 5,
    "bottom": 20,
    "delta": 3
  },
  "scrollTopPrev": 10,
  "scrollTopCur": 13
}

关键模式

Hardware Scroll vs Full Rewrite

scrollTop change only → DECSTBM + SU/SD → hardware scroll → skip full viewport rewrite
# 只有scrollTop变化
# 使用硬件滚动
# 避免全viewport重写
# 大幅减少IO

Scroll Region Margins

DECSTBM: CSI top ; bottom r → scroll region → only region rows shift
# DECSTBM设置滚动区域
# 只有区域内rows滚动
# 其他rows保持

CSI n S vs CSI n T

delta > 0: CSI n S (scroll down, content up) | delta < 0: CSI n T (scroll up, content down)
# delta正负决定CSI sequence
# CSI n S: scroll down n lines
# CSI n T: scroll up n lines

scrollTop Diff Only

scrollTop change + nothing else moved → hardware scroll eligible
# scrollTop变化是唯一条件
# 无其他layout shift
# 硬件滚动优化eligible

借用价值

• ⭐⭐⭐⭐⭐ DECSTBM hardware scroll optimization
• ⭐⭐⭐⭐⭐ ScrollHint type pattern
• ⭐⭐⭐⭐⭐ CSI n S/CSI n T sequences
• ⭐⭐⭐⭐⭐ scrollTop change detection
• ⭐⭐⭐⭐ Scroll region margins pattern

来源

• Claude Code: ink/render-node-to-output.ts (1462 lines)
• 分析报告: P49-3