feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

desktop/src-tauri/crates/buzz-terminal/src/damage.rs

@@ -0,0 +1,490 @@
+//! Turning grid changes into frames for the renderer.
+//!
+//! Two rules shape this module, both measured:
+//!
+//! 1. **Nothing but reading and copying happens under the `Term` lock.** The
+//!    caller copies rows out; encoding, hashing and serializing run after the
+//!    lock is released. Encoding inline costs ~75x in lock hold.
+//! 2. **Damage over-reports.** `Term::damage()` marks the cursor line every
+//!    call, so an idle terminal reports damage nearly every frame. Per-line
+//!    content hashing suppresses those, so the transport never sees a no-op.
+//!
+//! # Why a frame is the whole viewport
+//!
+//! Nearly every frame is a full repaint: `Term::scroll_up_relative` calls
+//! `mark_fully_damaged()` unconditionally, so any output reaching the bottom
+//! row damages the whole grid. Partial damage is effectively the idle cursor.
+//!
+//! That is fine, and the reason is worth having here rather than in a review
+//! thread. A full frame is O(viewport) *by construction* -- the grid is itself
+//! the coalescing buffer -- so its cost does not depend on how fast the child
+//! writes. Measured on a 200x50 grid, bytes per frame across four orders of
+//! magnitude of output rate: 11,390 at an unthrottled flood (45,759 lines
+//! scrolled per frame), 11,390 at ~1 MB/s, 11,390 at ~100 KB/s, 11,305 on a
+//! slow build log. Constant to three digits.
+//!
+//! A scroll-aware diff inverts that: its cost is O(lines scrolled), unbounded,
+//! and at 45,759 lines/frame it would ship ~915x more data than the full grid
+//! it was optimising. It wins where nobody is watching and loses under `cat`.
+//!
+//! **Revisit if the viewport grows.** 80x24 costs 2.6 KB/frame (0.2 MB/s at
+//! 60 Hz), 200x50 costs 11.4 KB (0.7 MB/s), 400x100 costs 42.8 KB (2.6 MB/s).
+//! 400x100 is roughly 4x a typical maximised window and is where this decision
+//! should be re-measured -- as a serialization/IPC question, not a damage one.
+//!
+//! Dedup earns its place in the interactive case rather than the streaming one:
+//! typing is ~0.9 rows per keystroke, and an idle terminal ships 0 rows across
+//! 60 frames instead of a cursor-line frame 60x/second. Idle is the load-bearing
+//! one -- it is what the substrate does while sitting behind the GUI untouched.
+
+use std::collections::hash_map::DefaultHasher;
+use std::hash::{Hash, Hasher};
+
+use alacritty_terminal::grid::Dimensions;
+use alacritty_terminal::index::{Column, Line};
+use alacritty_terminal::term::cell::{Cell, Flags};
+use alacritty_terminal::term::TermDamage;
+
+/// A run of cells sharing one visual style **and one cell width**.
+///
+/// # Why the consumer can position every cluster without Unicode tables
+///
+/// The renderer must place each display cluster at its true column, and it
+/// cannot derive that from the text: no single split rule over a concatenated
+/// string is correct. A regional-indicator flag (`U+1F1FA U+1F1F8`) is two
+/// ordinary one-column cells, so it must split *per codepoint*; a keycap
+/// (`1 U+FE0F U+20E3`) is one cell holding three codepoints, so it must split
+/// *per grapheme*. Those rules disagree, and the distinction lives in the grid,
+/// not in the string.
+///
+/// So the run carries it instead. Within a span every cluster advances the same
+/// [`width`](Self::width) columns, and [`cluster_count`](Self::cluster_count)
+/// says how many clusters the text holds. The consumer's rule is arithmetic on
+/// those two numbers, with no Unicode table anywhere:
+///
+/// ```text
+/// cluster_count == 1  -> the whole text is one cluster, at `column`
+/// otherwise           -> cluster i is the i-th char, at `column + i * width`
+/// ```
+///
+/// The second case is exact because a cell carrying zerowidth marks is always
+/// emitted alone, so every cell in a multi-cluster span contributes exactly one
+/// `char`.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Span {
+    /// First column of the run.
+    pub column: usize,
+    /// The run's text. Grapheme clusters are kept whole: a cell's zerowidth
+    /// combining marks follow its base character, so the renderer never sees
+    /// a base and its accent as separate glyphs.
+    pub text: String,
+    /// Columns each cluster in this run occupies: 1, or 2 for wide glyphs.
+    ///
+    /// Uniform across the run by construction -- a width change ends the span.
+    /// This is what lets the consumer position clusters by computed origin
+    /// rather than by accumulated text advance.
+    pub width: u8,
+    /// How many display clusters [`text`](Self::text) holds.
+    ///
+    /// Without this the consumer cannot distinguish a one-cluster span carrying
+    /// combining marks from an ordinary multi-character run, and would need a
+    /// Unicode zerowidth table to guess. The grid already knows, so it says.
+    pub cluster_count: u16,
+    /// Packed style: fg, bg, and attribute flags.
+    pub style: Style,
+}
+
+impl Span {
+    /// The decoding invariant, stated once: a span is either a single cluster
+    /// (which may hold several `char`s, as a keycap or an accented letter
+    /// does) or one cluster per `char`.
+    ///
+    /// Exposed so consumers can assert it at a trust boundary rather than
+    /// restate it. The encoder checks it in debug builds on every frame.
+    pub fn counts_are_consistent(&self) -> bool {
+        self.cluster_count == 1 || usize::from(self.cluster_count) == self.text.chars().count()
+    }
+}
+
+/// Visual style of a span, as the renderer needs it.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Style {
+    pub fg: u32,
+    pub bg: u32,
+    pub flags: u16,
+}
+
+/// One changed row.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RowFrame {
+    pub line: usize,
+    /// Whether this row continues onto the next screen row without a hard
+    /// line break. Retained separately from visual style so copy serialization
+    /// can reconstruct logical lines without exposing geometry flags to spans.
+    pub wrapped: bool,
+    pub spans: Vec<Span>,
+}
+
+/// The cursor, carried separately from row content.
+///
+/// Upstream damages the cursor's line on every `damage()` call. If the cursor
+/// travelled inside the row payload, every frame would carry a row rewrite for
+/// a caret that moved one column. As its own plane it costs a few bytes and
+/// leaves row dedup free to suppress the row.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct CursorFrame {
+    pub line: usize,
+    pub column: usize,
+    pub visible: bool,
+}
+
+/// One update for the renderer.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Frame {
+    pub rows: Vec<RowFrame>,
+    pub cursor: CursorFrame,
+    /// Whether the cursor plane changed since this encoder's previous frame.
+    /// Cursor movement can be the only visible effect of input (for example,
+    /// echoing a space over an already blank cell), so it independently makes
+    /// an incremental frame publishable.
+    pub cursor_changed: bool,
+    /// Whether the renderer should discard what it has and repaint.
+    pub full: bool,
+    /// The grid this frame describes. A change means the terminal was resized
+    /// and row indices refer to a different geometry than the previous frame's.
+    /// Carried so the consumer can detect that from the frame itself instead of
+    /// trusting that no resize overtook it in flight -- across a transport, a
+    /// frame captured before a resize can arrive after it.
+    pub viewport: crate::Viewport,
+}
+
+impl Frame {
+    /// True when there is nothing for the renderer to do.
+    pub fn is_empty(&self) -> bool {
+        self.rows.is_empty() && !self.cursor_changed && !self.full
+    }
+}
+
+/// Raw rows copied out from under the lock, awaiting encode.
+pub struct RawFrame {
+    rows: Vec<(usize, Vec<Cell>)>,
+    cursor: CursorFrame,
+    full: bool,
+    viewport: crate::Viewport,
+}
+
+/// The grid line a screen row reads from.
+///
+/// The grid indexes the active area from 0 and scrollback with *negative*
+/// lines, so scrolling back `n` lines means every screen row reads `n` lines
+/// higher. At the live edge the offset is zero and this is the identity, which
+/// is why the unscrolled path is unchanged rather than merely equivalent.
+fn row_of(screen_row: usize, display_offset: usize) -> Line {
+    Line(screen_row as i32 - display_offset as i32)
+}
+
+/// Where the cursor sits on screen, given how far the viewport is scrolled
+/// back.
+///
+/// The grid keeps the cursor in *active-area* coordinates, which do not move
+/// when the user scrolls; the renderer paints *screen rows*, which do. The two
+/// agree only at the live edge, so the conversion has to happen somewhere, and
+/// it happens here rather than in the renderer -- the renderer is not told the
+/// display offset, and giving it one would put this same arithmetic on the far
+/// side of a transport.
+///
+/// Scrolling far enough pushes the cursor off the bottom of the viewport, and
+/// then it is reported as not visible. Without that clamp a caret drawn at a
+/// clamped row would sit on some unrelated line of history, which reads as
+/// corruption rather than as scrollback.
+fn cursor_frame(
+    cursor_point: alacritty_terminal::index::Point,
+    display_offset: usize,
+    screen_lines: usize,
+    shown: bool,
+) -> CursorFrame {
+    let line = cursor_point.line.0.max(0) as usize + display_offset;
+    CursorFrame {
+        line: line.min(screen_lines.saturating_sub(1)),
+        column: cursor_point.column.0,
+        visible: shown && line < screen_lines,
+    }
+}
+
+/// Copy the damaged rows out of the terminal. **Runs under the lock; does no
+/// encoding.** Keep this function boring — everything added here is lock hold.
+pub fn capture(terminal: &mut crate::Terminal) -> RawFrame {
+    let viewport = terminal.viewport();
+    let display_offset = terminal.display_offset();
+    let term = terminal.term_mut();
+    let columns = term.columns();
+    let screen_lines = term.screen_lines();
+    let cursor_point = term.grid().cursor.point;
+    let shown = term
+        .mode()
+        .contains(alacritty_terminal::term::TermMode::SHOW_CURSOR);
+
+    // Upstream's partial iterator already reports **screen** rows: it offsets
+    // each damaged active-area line by the display offset and drops the ones
+    // that scrolling pushed off the bottom (`TermDamageIterator::new`). So both
+    // arms below speak the same coordinate, and `row_of` converts once.
+    let (lines, full) = match term.damage() {
+        TermDamage::Full => ((0..screen_lines).collect::<Vec<_>>(), true),
+        TermDamage::Partial(iter) => (
+            iter.map(|bounds| bounds.line)
+                .filter(|l| *l < screen_lines)
+                .collect(),
+            false,
+        ),
+    };
+
+    let grid = term.grid();
+    let mut rows = Vec::with_capacity(lines.len());
+    for line in lines {
+        let row = &grid[row_of(line, display_offset)];
+        rows.push((line, row[..Column(columns)].to_vec()));
+    }
+    let cursor = cursor_frame(cursor_point, display_offset, screen_lines, shown);
+
+    term.reset_damage();
+    RawFrame {
+        rows,
+        cursor,
+        full,
+        viewport,
+    }
+}
+
+/// Copy the **entire visible viewport**, leaving damage untouched.
+///
+/// This exists for subscribers that arrive mid-stream: attach, reattach, and
+/// the successor side of a resize. Damage only describes what changed since
+/// the last capture, so a newcomer that starts from [`capture`] sees whatever
+/// happened to change next -- often just the cursor's line -- painted onto a
+/// blank screen. Upstream's `mark_fully_damaged` is private, so an embedder
+/// cannot ask for a full frame that way.
+///
+/// **It must not consume damage, and that is the load-bearing property.** The
+/// incumbent subscriber's next [`capture`] has to still see its rows. If this
+/// called `damage()`/`reset_damage()` it would steal them, and the incumbent
+/// would freeze on stale content while a newcomer's full-frame test passed.
+/// The absence of those two calls below is the mechanism; `snapshot_test.rs`
+/// is the proof.
+///
+/// **Runs under the lock; does no encoding.** Costs a full grid copy rather
+/// than a damaged-rows copy, so it belongs on attach, not in the frame loop.
+pub fn capture_all(terminal: &mut crate::Terminal) -> RawFrame {
+    let viewport = terminal.viewport();
+    let display_offset = terminal.display_offset();
+    let term = terminal.term_mut();
+    let columns = term.columns();
+    let screen_lines = term.screen_lines();
+    let cursor_point = term.grid().cursor.point;
+    let shown = term
+        .mode()
+        .contains(alacritty_terminal::term::TermMode::SHOW_CURSOR);
+
+    let grid = term.grid();
+    let mut rows = Vec::with_capacity(screen_lines);
+    for line in 0..screen_lines {
+        let row = &grid[row_of(line, display_offset)];
+        rows.push((line, row[..Column(columns)].to_vec()));
+    }
+    let cursor = cursor_frame(cursor_point, display_offset, screen_lines, shown);
+
+    // No `damage()` and no `reset_damage()`: see the note above.
+    RawFrame {
+        rows,
+        cursor,
+        // A snapshot *is* a repaint, and marking it full also resets the
+        // consumer's `Encoder` hashes, so its dedup state describes the grid it
+        // was actually given rather than a predecessor's.
+        full: true,
+        viewport,
+    }
+}
+
+/// Suppresses rows whose content did not actually change.
+#[derive(Default)]
+pub struct Encoder {
+    hashes: Vec<u64>,
+    cursor: Option<CursorFrame>,
+}
+
+impl Encoder {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Encode a captured frame. **Runs with the lock released.**
+    pub fn encode(&mut self, raw: RawFrame) -> Frame {
+        // A full frame invalidates the dedup cache. Both routes that produce
+        // one matter: a `mark_fully_damaged` from scroll/alt-swap, and a resize,
+        // where the cached hashes describe rows of a different width entirely.
+        if raw.full {
+            self.hashes.clear();
+        }
+        let mut rows = Vec::with_capacity(raw.rows.len());
+        for (line, cells) in raw.rows {
+            let hash = hash_cells(&cells);
+            if self.hashes.len() <= line {
+                self.hashes.resize(line + 1, 0);
+            }
+            if self.hashes[line] == hash {
+                continue;
+            }
+            self.hashes[line] = hash;
+            rows.push(RowFrame {
+                line,
+                wrapped: cells
+                    .last()
+                    .is_some_and(|cell| cell.flags.contains(Flags::WRAPLINE)),
+                spans: spans(&cells),
+            });
+        }
+        let cursor_changed = self.cursor != Some(raw.cursor);
+        self.cursor = Some(raw.cursor);
+        Frame {
+            rows,
+            cursor: raw.cursor,
+            cursor_changed,
+            full: raw.full,
+            viewport: raw.viewport,
+        }
+    }
+}
+
+fn hash_cells(cells: &[Cell]) -> u64 {
+    let mut hasher = DefaultHasher::new();
+    for cell in cells {
+        cell.c.hash(&mut hasher);
+        // Hash the *packed* colors, not the enum: this is the representation
+        // the renderer receives, so the dedup key cannot disagree with the
+        // wire encoding and suppress a row that actually changed on screen.
+        pack_color(cell.fg).hash(&mut hasher);
+        pack_color(cell.bg).hash(&mut hasher);
+        cell.flags.bits().hash(&mut hasher);
+        if let Some(zerowidth) = cell.zerowidth() {
+            zerowidth.hash(&mut hasher);
+        }
+    }
+    hasher.finish()
+}
+
+/// Group a row's cells into runs of uniform style and width.
+///
+/// A run continues only while style *and* width match, and a cell carrying
+/// zerowidth marks is always emitted alone. Both breaks exist so the consumer
+/// can compute each cluster's column as `column + i * width`; see [`Span`].
+///
+/// The width comparison is the only thing keeping widths uniform within a run:
+/// [`Style`] deliberately excludes [`GEOMETRY_FLAGS`], so a style key cannot
+/// break a run on width behind this check's back.
+fn spans(cells: &[Cell]) -> Vec<Span> {
+    let mut spans: Vec<Span> = Vec::new();
+    // Whether the run in progress may still be extended. Kept here rather than
+    // on `Span` because it is grouping bookkeeping, not part of the wire shape.
+    let mut open = false;
+    for (column, cell) in cells.iter().enumerate() {
+        // A wide glyph occupies two cells: the character, then a spacer. The
+        // spacer carries no text of its own -- emitting its placeholder space
+        // would insert a phantom column after every CJK character or emoji.
+        if cell.flags.contains(Flags::WIDE_CHAR_SPACER) {
+            continue;
+        }
+        let style = style_of(cell);
+        let width = if cell.flags.contains(Flags::WIDE_CHAR) {
+            2
+        } else {
+            1
+        };
+        let zerowidth = cell.zerowidth();
+        let mut text = String::new();
+        text.push(cell.c);
+        if let Some(marks) = zerowidth {
+            text.extend(marks);
+        }
+
+        // A cluster with combining marks holds more `char`s than columns, so it
+        // cannot share a run: it is the one case where "one char per cluster"
+        // stops holding.
+        let joinable = zerowidth.is_none();
+        match spans.last_mut() {
+            // `cluster_count` is refused rather than wrapped when it would
+            // overflow: the run simply ends and a new span starts at this
+            // column, which the consumer's rule already handles.
+            Some(last)
+                if open
+                    && joinable
+                    && last.style == style
+                    && last.width == width
+                    && last.cluster_count < u16::MAX =>
+            {
+                last.text.push_str(&text);
+                last.cluster_count += 1;
+            }
+            _ => spans.push(Span {
+                column,
+                text,
+                width,
+                cluster_count: 1,
+                style,
+            }),
+        }
+        open = joinable;
+    }
+    // Enforced in release, not just in debug. This is a *wire* invariant: a
+    // span that violates it is undecodable by the rule in [`Span`], and the
+    // consumer's failure is silent misplacement of every cluster after it.
+    // A `debug_assert` here would vanish in exactly the build where that
+    // corruption ships. The cost is one pass over text already in cache --
+    // the same order as building the spans -- and it buys a loud, local
+    // failure instead of a renderer quietly drawing the wrong columns.
+    assert!(
+        spans.iter().all(Span::counts_are_consistent),
+        "cluster_count must be 1 or the span's char count"
+    );
+    spans
+}
+
+/// Flags describing where a cell sits in the grid rather than how it looks.
+///
+/// `WRAPLINE` marks the last cell of a row that wrapped; the three wide-char
+/// bits mark a two-column glyph and its spacer. Neither says anything about
+/// appearance.
+///
+/// These are excluded from [`Style`] so the style key means one thing: visual
+/// attributes. Geometry travels in [`Span::width`], which is compared on its
+/// own when grouping -- if these bits stayed in the key they would break runs
+/// as a side effect and leave the width comparison untestable.
+///
+/// Composite visual aliases (`BOLD_ITALIC`, `DIM_BOLD`, `ALL_UNDERLINES`) are
+/// deliberately not masked: those are appearance.
+const GEOMETRY_FLAGS: Flags = Flags::WRAPLINE
+    .union(Flags::WIDE_CHAR)
+    .union(Flags::WIDE_CHAR_SPACER)
+    .union(Flags::LEADING_WIDE_CHAR_SPACER);
+
+fn style_of(cell: &Cell) -> Style {
+    Style {
+        fg: pack_color(cell.fg),
+        bg: pack_color(cell.bg),
+        flags: cell.flags.difference(GEOMETRY_FLAGS).bits(),
+    }
+}
+
+/// Pack a color into a tagged u32 the renderer resolves against the theme.
+///
+/// Named and indexed colors stay symbolic rather than being resolved here:
+/// the substrate must follow the user's chosen theme, so the palette belongs
+/// to the renderer, not to a snapshot taken at damage time.
+fn pack_color(color: alacritty_terminal::vte::ansi::Color) -> u32 {
+    use alacritty_terminal::vte::ansi::Color;
+    match color {
+        Color::Named(named) => 0x0100_0000 | named as u32,
+        Color::Indexed(index) => 0x0200_0000 | index as u32,
+        Color::Spec(rgb) => {
+            0x0300_0000 | ((rgb.r as u32) << 16) | ((rgb.g as u32) << 8) | rgb.b as u32
+        }
+    }
+}