Add optional tree-sitter declaration context

1 files changed, 103 insertions, 45 deletions

diff --git a/src/panes.zig b/src/panes.zig
index b2f05cdf..32fe8c28 100644
--- a/src/panes.zig
+++ b/src/panes.zig
@@ -166,6 +166,9 @@ pub const Pane = struct {
     wrap_line: [limits.wrap_rows]i32 = undefined,
     wrap_col: [limits.wrap_rows]i32 = undefined,
     wrap_n: u16 = 0,
+    /// A row map also exists for sticky headers when soft wrapping is off.
+    body_wrapped: bool = false,
+    context_rows: u16 = 0,
     sel: [3]Sel = @splat(.{}),
     pointer_selections: [3]?PointerSelection = @splat(null),
     next_pointer_selection: u64 = 0,
@@ -352,30 +355,41 @@ pub const Pane = struct {
     }
 
     pub fn ensureCursorVisible(pane: *Pane) void {
-        // scrolloff margin, shrunk on short panes so the band stays non-empty
-        var margin: i32 = @min(config.scroll_off, @divTrunc(@as(i32, pane.rows) - 1, 2));
         const off = pane.scroll();
+        var in_context = false;
+        // Maps survive until the next render. A jump may have changed scroll
+        // already, so only treat an ancestor as pinned in the matching view.
+        if (pane.context_rows < pane.wrap_n and pane.wrap_line[pane.context_rows] == off) {
+            for (pane.wrap_line[0..pane.context_rows]) |row| {
+                if (row == pane.cur_row) {
+                    in_context = true;
+                    break;
+                }
+            }
+        }
+        // Scrolloff is measured in the ordinary body, excluding sticky rows.
+        var margin: i32 = @min(config.scroll_off, @divTrunc(@as(i32, pane.rows) - 1, 2));
         var last = off + @as(i32, pane.rows) - 1;
-        if (pane.wrap_n > 0) {
-            const lines_shown = pane.wrap_line[pane.wrap_n - 1] - pane.wrap_line[0];
+        if (pane.context_rows < pane.wrap_n) {
+            const lines_shown = pane.wrap_line[pane.wrap_n - 1] - pane.wrap_line[pane.context_rows];
             last = off + lines_shown;
             margin = @min(margin, @divTrunc(@max(0, lines_shown), 2));
         }
-        if (pane.cur_row < off + margin) {
-            pane.scrollBy(pane.cur_row - margin - off); // scrollBy clamps at line 0
-        } else if (pane.cur_row > last - margin) {
-            // don't scroll a file past EOF-at-bottom-row (vim's bottom clamp);
-            // terminals overshoot harmlessly — the vt clamps at the live bottom
-            var to = pane.cur_row + margin;
-            if (pane.file) |*f| to = @min(to, @as(i32, @intCast(File.nlines(pane.gpa, f) -| 1)));
-            if (comptime Pdf.enabled) {
-                if (pane.pdf) |pv|
-                    to = @min(to, @as(i32, @intCast(modal.lineCount(pv.text) -| 1)));
+        if (!in_context) {
+            if (pane.cur_row < off + margin) {
+                pane.scrollBy(pane.cur_row - margin - off);
+            } else if (pane.cur_row > last - margin) {
+                var to = pane.cur_row + margin;
+                if (pane.file) |*f| to = @min(to, @as(i32, @intCast(File.nlines(pane.gpa, f) -| 1)));
+                if (comptime Pdf.enabled) {
+                    if (pane.pdf) |pv|
+                        to = @min(to, @as(i32, @intCast(modal.lineCount(pv.text) -| 1)));
+                }
+                pane.scrollBy(@max(0, to - last));
             }
-            pane.scrollBy(@max(0, to - last));
         }
         if (pane.file) |f| {
-            if (pane.wrap_n != 0) return;
+            if (pane.body_wrapped) return;
             const w: i32 = @max(1, @as(i32, pane.cols) - @as(i32, File.gutterWidth(pane)));
             const hmargin: i32 = @min(config.scroll_off, @divTrunc(w - 1, 2));
             const line = modal.lineSlice(f.content, @intCast(@max(0, pane.cur_row)));
@@ -999,6 +1013,9 @@ pub const File = struct {
         highlights: []u8 = &.{},
         highlight_start: usize = 0,
         syntax_dirty: bool = true,
+        tree_context: bool = false,
+        context_declarations: []syntax.ContextDeclaration = &.{},
+        context_revision: ?u32 = null,
         history: *History,
     };
 
@@ -1022,6 +1039,7 @@ pub const File = struct {
             .vweight = pane.vweight,
             .collapsed = pane.collapsed,
             .file = .{
+                .tree_context = file.tree_context,
                 .path = file.path,
                 .content = file.content,
                 .content_b64 = try dump.encodeBytes(arena, file.content),
@@ -1502,6 +1520,7 @@ pub const File = struct {
             .revision = @intFromBool(saved.dirty),
             .history = history,
         };
+        pane.file.?.tree_context = saved.tree_context and supportsContext(pane);
         pane.cur_pinned = true;
         pane.cur_row = @intCast(src.scroll);
         pane.cols = @max(1, src.cols);
@@ -1519,6 +1538,7 @@ pub const File = struct {
         if (file.mini) |*mini| mini.deinit(p.gpa);
         if (file.line_starts.len > 0) p.gpa.free(file.line_starts);
         if (file.highlights.len > 0) p.tree_sitter_gpa.free(file.highlights);
+        if (file.context_declarations.len > 0) p.tree_sitter_gpa.free(file.context_declarations);
         for (file.history.undo[0..file.history.undo_len]) |snap| p.gpa.free(snap.content);
         for (file.history.redo[0..file.history.redo_len]) |snap| p.gpa.free(snap.content);
         p.gpa.destroy(file.history);
@@ -1656,6 +1676,12 @@ pub const File = struct {
             const pane = slot orelse continue;
             if (pane.file == null) continue;
             const f = &pane.file.?;
+            if (f.tree_context and supportsContext(pane) and f.context_revision != f.revision) {
+                const declarations = syntax.contextDeclarations(p.tree_sitter_gpa, f.path, f.content) catch continue;
+                if (f.context_declarations.len > 0) p.tree_sitter_gpa.free(f.context_declarations);
+                f.context_declarations = declarations;
+                f.context_revision = f.revision;
+            }
             if (f.mini != null) {
                 f.syntax_dirty = false;
                 continue;
@@ -1670,14 +1696,15 @@ pub const File = struct {
             }
             const need_start = lineStart(p.gpa, f, f.scroll);
             const need_end = @max(need_start, lineStart(p.gpa, f, f.scroll + pane.rows + SYNTAX_CONTEXT_AFTER_ROWS));
-            if (f.highlights.len > 0 and need_start >= f.highlight_start and
+            if ((!f.tree_context or (f.highlight_start == 0 and f.highlights.len == f.content.len)) and
+                f.highlights.len > 0 and need_start >= f.highlight_start and
                 need_end <= f.highlight_start + f.highlights.len)
             {
                 f.syntax_dirty = false;
                 continue;
             }
             const slack: usize = if (f.highlights.len == 0) 0 else pane.rows;
-            const whole = pane.colorAlgo() == .locations;
+            const whole = pane.colorAlgo() == .locations or f.tree_context;
             const start = if (whole) 0 else lineStart(p.gpa, f, f.scroll -| slack);
             const end = if (whole)
                 f.content.len
@@ -1698,6 +1725,28 @@ pub const File = struct {
         }
     }
 
+    pub fn supportsContext(pane: *const Pane) bool {
+        const file = pane.file orelse return false;
+        return file.output == null and file.mini == null and syntax.supportsPath(file.path);
+    }
+
+    fn prepareContextRows(pane: *Pane, file: *State) void {
+        pane.context_rows = 0;
+        if (!file.tree_context or !supportsContext(pane) or pane.rows > pane.wrap_line.len) return;
+        const capacity = pane.rows -| 1; // retain at least one ordinary body row
+        for (file.context_declarations) |declaration| {
+            if (declaration.start_line >= file.scroll) break;
+            if (declaration.end_line < file.scroll) continue;
+            var row = declaration.start_line;
+            while (row <= declaration.header_end_line and row < file.scroll) : (row += 1) {
+                if (pane.context_rows >= capacity) return;
+                if (pane.context_rows > 0 and row <= pane.wrap_line[pane.context_rows - 1]) continue;
+                pane.wrap_line[pane.context_rows] = @intCast(row);
+                pane.context_rows += 1;
+            }
+        }
+    }
+
     pub fn wrapWidth(pane: *const Pane, wrap: bool) usize {
         if (!wrap or pane.rows > pane.wrap_line.len) return 0;
         return @max(1, @as(usize, pane.cols -| gutterWidth(pane)) -| 1);
@@ -1717,6 +1766,8 @@ pub const File = struct {
 
     pub fn bodyText(arena: std.mem.Allocator, pane: *Pane, f: *State, wrap: bool) ![]const u8 {
         const width = wrapWidth(pane, wrap);
+        pane.body_wrapped = width > 0;
+        prepareContextRows(pane, f);
         pane.wrap_n = 0;
 
         const len = fillBody(null, pane, f, width, false);
@@ -1731,32 +1782,37 @@ pub const File = struct {
     fn fillBody(dst: ?[]u8, pane: *Pane, f: *State, width: usize, record_wrap: bool) usize {
         if (record_wrap) pane.wrap_n = 0;
         const prefix_width = gutterWidth(pane);
-        // start ON the first visible line instead of walking the file to it: this
-        // walk was O(f.scroll) and recolorSyntax below ran the identical one again
-        var flines = std.mem.splitScalar(u8, f.content[lineStart(pane.gpa, f, f.scroll)..], '\n');
-        if (f.scroll >= nlines(pane.gpa, f)) _ = flines.next();
-        // the line the NEXT row comes from and the byte column of it that row
-        // starts at — the two the map records, walked forward by the loop
-        var abs: i32 = @intCast(f.scroll);
-        var at: usize = 0;
-        var cur = flines.next();
+        const total = nlines(pane.gpa, f);
+        var body_line: usize = f.scroll;
+        var body_at: usize = 0;
         var written: usize = 0;
         for (0..pane.rows) |i| {
             if (i > 0) {
                 if (dst) |out| out[written] = '\n';
                 written += 1;
             }
-            if (width > 0 and record_wrap) {
-                pane.wrap_line[i] = abs;
-                pane.wrap_col[i] = @intCast(at);
+            const context = i < pane.context_rows;
+            const row = if (context) @as(usize, @intCast(pane.wrap_line[i])) else body_line;
+            const at = if (context) 0 else body_at;
+            const text = if (row < total) sourceLine(pane, @intCast(row)) else "";
+            // Headers use one screen row per source row, preserving signatures
+            // without allowing a long ancestor to consume the whole viewport.
+            const end = if (width == 0 or context) text.len else fitEnd(text, at, width);
+            const cut = if (pane.hscroll > 0 and width == 0)
+                modal.graphemeStart(text, @min(@as(usize, @intCast(pane.hscroll)), text.len))
+            else
+                at;
+            if ((width > 0 or pane.context_rows > 0) and record_wrap) {
+                pane.wrap_line[i] = @intCast(row);
+                pane.wrap_col[i] = @intCast(cut);
                 pane.wrap_n = @intCast(i + 1);
             }
-            if (cur) |text| {
+            if (row < total) {
                 var lbuf: [@max(config.PREFIX_W, 32)]u8 = undefined;
                 const prefix = lbuf[0..prefix_width];
                 @memset(prefix, ' ');
                 if (at == 0) {
-                    var lineno: usize = @intCast(abs + 1);
+                    var lineno = row + 1;
                     var digit: usize = prefix.len - 1;
                     while (true) {
                         digit -= 1;
@@ -1767,24 +1823,18 @@ pub const File = struct {
                 }
                 if (dst) |out| @memcpy(out[written..][0..prefix.len], prefix);
                 written += prefix.len;
-
-                const end = if (width == 0) text.len else fitEnd(text, at, width);
-                const take = end - at;
-                const cut = if (pane.hscroll > 0 and width == 0)
-                    modal.graphemeStart(text[at..end], @min(@as(usize, @intCast(pane.hscroll)), take))
-                else
-                    0;
-                const shown = text[at + cut .. end];
+                const shown = text[cut..end];
                 if (dst) |out| @memcpy(out[written..][0..shown.len], shown);
                 written += shown.len;
+            }
+            if (!context) {
                 if (width > 0 and end < text.len) {
-                    at = end;
+                    body_at = end;
                 } else {
-                    abs += 1;
-                    at = 0;
-                    cur = flines.next();
+                    body_line += 1;
+                    body_at = 0;
                 }
-            } else abs += 1;
+            }
         }
         return written;
     }
@@ -1798,6 +1848,14 @@ pub const File = struct {
         const cur_line: i32 = if (active and !pane.tag_edit) gcrow else std.math.minInt(i32);
         // the body's first row, the way renderPane derives it (Tagbottom)
         const body_y = if (p.settings.tag_bottom) r.y else r.y + pardes.BOX_H;
+        const context_bg = p.theme().tag_bg;
+        for (0..@min(pane.context_rows, body_h)) |context_row| {
+            for (0..tw) |col| {
+                const cell = s.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(context_row)));
+                cell.default = false;
+                cell.style.bg = .{ .rgb = context_bg };
+            }
+        }
         var vr: u16 = 0;
         while (vr < body_h) : (vr += 1) {
             const row_line: i32 = if (pane.wrap_n == 0)