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Deepen pyte vs GoPyte capture requirements

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@@ -400,7 +400,7 @@ Not yet started. This would be a separate project (`textual-webterm-go`) providi
## pyte vs GoPyte: Thorough Comparison ## pyte vs GoPyte: Thorough Comparison
This section compares the Python **pyte** terminal emulator and the Go **GoPyte** emulator (per their upstream documentation/README). The focus is on capture accuracy, Unicode handling, performance expectations, and integration risk for textual-webterm. This section compares the Python **pyte** terminal emulator and the Go **GoPyte** emulator (per their upstream documentation/README). The focus is on capture accuracy, Unicode handling, performance expectations, and integration risk for textual-webterm. Where GoPyte details are unclear, we call them out explicitly as validation items.
### Feature Matrix (Capture-Relevant) ### Feature Matrix (Capture-Relevant)
@@ -412,20 +412,24 @@ This section compares the Python **pyte** terminal emulator and the Go **GoPyte*
| **Scrollback/history** | HistoryScreen (configurable) | Built-in scrollback (claims) | Semantics may differ; check memory cost. | | **Scrollback/history** | HistoryScreen (configurable) | Built-in scrollback (claims) | Semantics may differ; check memory cost. |
| **Resize behavior** | Resizes + cursor + dirty state | Resizes + content (claims) | Must preserve content on resize. | | **Resize behavior** | Resizes + cursor + dirty state | Resizes + content (claims) | Must preserve content on resize. |
| **SGR attributes** | Bold/underline/reverse/color | SGR attrs (claims) | Verify italics, faint, strikethrough. | | **SGR attributes** | Bold/underline/reverse/color | SGR attrs (claims) | Verify italics, faint, strikethrough. |
| **Underline styles** | Basic underline | Unknown | Double/curly underline may be missing. |
| **Color depth** | ANSI + 256 + (truecolor in practice) | ANSI + 256? (verify) | Truecolor required for accurate screenshots. | | **Color depth** | ANSI + 256 + (truecolor in practice) | ANSI + 256? (verify) | Truecolor required for accurate screenshots. |
| **DEC special graphics** | Supported (line drawing) | Unknown | Box-drawing is critical for TUIs. | | **DEC special graphics** | Supported (line drawing) | Unknown | Box-drawing is critical for TUIs. |
| **Character sets (G0/G1)** | Supported | Unknown | Needed for legacy line-drawing. |
| **Scroll regions** | Supported | Unknown | Needed for curses-style UI. | | **Scroll regions** | Supported | Unknown | Needed for curses-style UI. |
| **Insert/delete (IL/DL/ICH/DCH)** | Supported | Unknown | Affects screen fidelity during updates. | | **Insert/delete (IL/DL/ICH/DCH)** | Supported | Unknown | Affects screen fidelity during updates. |
| **Tabs / tab stops** | Supported | Unknown | UI alignment depends on tabs. | | **Tabs / tab stops** | Supported | Unknown | UI alignment depends on tabs. |
| **Wrap / origin modes** | Supported | Unknown | Impacts cursor positioning and layout. | | **Autowrap/origin modes** | Supported | Unknown | Impacts cursor positioning and layout. |
| **Cursor save/restore** | Supported | Unknown | Common in TUIs and prompts. | | **Cursor save/restore** | Supported | Unknown | Common in TUIs and prompts. |
| **Cursor visibility/style** | Basic visibility | Unknown | Useful for accurate snapshots. |
| **Erase semantics (ED/EL)** | Supported | Unknown | Correct clearing is vital for screenshots. |
| **Unicode width** | wcwidth-style width | go-runewidth | Width differences can misalign SVG. | | **Unicode width** | wcwidth-style width | go-runewidth | Width differences can misalign SVG. |
| **Combining marks / ZWJ** | Unicode-aware | runewidth-based | Emoji sequences may differ in width. | | **Combining marks / ZWJ** | Unicode-aware | runewidth-based | Emoji sequences may differ in width. |
| **Dirty tracking** | Exposes dirty set / DiffScreen | Unknown | Needed for efficient screenshot caching. | | **Dirty tracking** | Exposes dirty set / DiffScreen | Unknown | Needed for efficient screenshot caching. |
| **Images (sixel/kitty)** | Not supported | Not supported | Not required, but a capture limitation. | | **Images (sixel/kitty)** | Not supported | Not supported | Not required, but a capture limitation. |
| **Performance** | Python, moderate | Go, claims high throughput | Benchmark under heavy output. | | **Performance** | Python, moderate | Go, claims high throughput | Benchmark under heavy output. |
| **API stability** | Mature, widely used | Newer, smaller ecosystem | Risk of breaking changes. | | **API stability** | Mature, widely used | Newer, smaller ecosystem | Risk of breaking changes. |
| **Test maturity** | Established | Claimed high coverage | Must run our own parity suite. | | **Test maturity** | Established | Claims high coverage | Must run our own parity suite. |
### Unicode & Emoji Handling (Critical for SVG Capture) ### Unicode & Emoji Handling (Critical for SVG Capture)
@@ -465,21 +469,35 @@ We depend on the emulator for **accurate snapshot state**, not just live display
- **Dirty tracking or diffability** to avoid re-rendering unchanged screens. - **Dirty tracking or diffability** to avoid re-rendering unchanged screens.
- Reliable **color mapping** (ANSI 16 + 256 + truecolor). - Reliable **color mapping** (ANSI 16 + 256 + truecolor).
- Correct **DEC line drawing** (box-drawing characters). - Correct **DEC line drawing** (box-drawing characters).
- Correct **erase semantics** (ED/EL) to avoid stale cells.
If any of these are missing, screenshots will be wrong or expensive to compute. If any of these are missing, screenshots will be wrong or expensive to compute.
### Capture-Enhancing (Nice-to-Have) Features
These aren’t required for parity, but would improve capture quality or UX:
- **OSC 8 hyperlink metadata** to annotate clickable URLs in SVG output.
- **Underline styles** (double/curly) for richer text attributes.
- **Cursor style/shape** metadata for accurate snapshots.
- **Grapheme cluster awareness** (emoji sequences treated as single cells).
- **Structured diffs** from emulator (explicit dirty regions instead of full screen).
### Known Gaps / Validation Checklist ### Known Gaps / Validation Checklist
Before relying on GoPyte for parity, verify: Before relying on GoPyte for parity, verify:
- [ ] Full-screen app behavior (vim, htop, less) with alt screen. - [ ] Full-screen app behavior (vim, htop, less) with alt screen.
- [ ] DEC line drawing / special graphics set (box-drawing correctness). - [ ] DEC line drawing / special graphics set (box-drawing correctness).
- [ ] Character set switching (G0/G1) for legacy graphics.
- [ ] Scroll regions (DECSTBM) and origin mode behavior. - [ ] Scroll regions (DECSTBM) and origin mode behavior.
- [ ] Insert/delete line/char (IL/DL/ICH/DCH) correctness. - [ ] Insert/delete line/char (IL/DL/ICH/DCH) correctness.
- [ ] Tab stops and tab clear (alignment in TUIs). - [ ] Tab stops and tab clear (alignment in TUIs).
- [ ] SGR coverage: bold/underline/italic/reverse + 256/truecolor. - [ ] SGR coverage: bold/underline/italic/reverse + 256/truecolor.
- [ ] Underline styles, faint, strikethrough.
- [ ] Unicode width parity with pyte (emoji + CJK samples). - [ ] Unicode width parity with pyte (emoji + CJK samples).
- [ ] Cursor save/restore (DECSC/DECRC) and visibility toggles. - [ ] Cursor save/restore (DECSC/DECRC) and visibility toggles.
- [ ] Erase semantics (ED/EL) and autowrap correctness.
- [ ] Resize correctness (content preservation, cursor placement). - [ ] Resize correctness (content preservation, cursor placement).
- [ ] Performance at high output rates (100k+ lines, low latency). - [ ] Performance at high output rates (100k+ lines, low latency).