A mouse sweep selects a stream, as acme's does, not a rectangle

A B1, B2 or B3 drag over several lines took the same columns from every row, a block. acme's sweep is a stream (libframe/frselect.c:115-140, frselectpaint; acme text.c:881, textselect): the first row from the press to its end, the rows between whole, the last from its start to the release. edit.sweepCols says which columns of a row a sweep takes; the captured spans, the text a sweep yields (copy, chords, B2 and B3 operands, a terminal's automatic yank) and the highlight all follow it, in bodies, multi-row tags, terminals and text-rendered PDFs; a row the sweep runs through is highlighted to the edge, and rows after the first leave out the line numbers. Native PDF selection was already MuPDF's stream. No pane keeps a rectangle. exec-bigdrag's golden changes: its middle sweep now runs whole lines.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

4 files changed, 64 insertions, 46 deletions

diff --git a/src/body_layer.zig b/src/body_layer.zig
index a0195fb8..413ab7de 100644
--- a/src/body_layer.zig
+++ b/src/body_layer.zig
@@ -72,7 +72,7 @@ fn paintTerminalSelection(p: *Pardes, s: *Surface, pane: *Pane, r: Rect, rows: [
             hi = @min(hi, line.len);
             if (lo >= hi) continue;
             var col = panes.File.rawDisplayCol(line, lo);
-            const end = panes.File.rawDisplayCol(line, hi);
+            const end = if (row.to_edge and hi == line.len) width else panes.File.rawDisplayCol(line, hi);
             while (col < end and col < width) : (col += 1) {
                 const cell = s.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(visible)));
                 cell.default = false;
@@ -103,7 +103,7 @@ fn paintSourceSelection(p: *Pardes, s: *Surface, pane: *Pane, r: Rect, rows: []c
             const hi = @min(end, row.hi);
             if (lo >= hi) continue;
             var col = prefix + @as(i32, @intCast(panes.File.rawDisplayCol(line[start..], lo - start)));
-            const last = prefix + @as(i32, @intCast(panes.File.rawDisplayCol(line[start..], hi - start)));
+            const last = if (row.to_edge and hi == end) @as(i32, width) else prefix + @as(i32, @intCast(panes.File.rawDisplayCol(line[start..], hi - start)));
             while (col < last and col < width) : (col += 1) {
                 const cell = s.at(tx + @as(u16, @intCast(col)), body_y + @as(u16, @intCast(visible)));
                 cell.default = false;
@@ -130,13 +130,12 @@ pub fn paintPointerSelection(
     fg: ?[3]u8,
 ) void {
     if (pane.pointerSelection(sl)) |rows| return paintSourceSelection(p, s, pane, r, rows, bg, fg);
-    const r0 = @min(sl.r0, sl.r1);
-    const r1 = @max(sl.r0, sl.r1);
-    const c0 = @max(0, @min(sl.c0, sl.c1));
-    const c1 = @max(0, @max(sl.c0, sl.c1));
     var row: u16 = 0;
     while (row < r.h) : (row += 1) {
-        if (@as(i32, row) < r0 or @as(i32, row) > r1 or row < from_row) continue;
+        if (row < from_row) continue;
+        const cols = edit.sweepCols(sl, row) orelse continue;
+        const c0: i32 = if (cols.first) cols.lo else 0;
+        const c1: i32 = cols.hi orelse std.math.maxInt(i16);
         const sy = if (row < pane.tag_rows) tag_y + row else body_y + row - pane.tag_rows;
         // File line numbers occupy a gutter only in the body. The tag is
         // row zero in Sel space and starts at its real first text cell.
diff --git a/src/edit.zig b/src/edit.zig
index 84bbb292..3dfe2f20 100644
--- a/src/edit.zig
+++ b/src/edit.zig
@@ -234,10 +234,13 @@ pub fn capturePointerSelection(p: *Pardes, pane: *Pane, slot: usize) !void {
     errdefer p.gpa.free(rows);
     const raw_text = if (raw) try p.gpa.dupe(u8, try selectionText(p, pane, gesture)) else null;
     const prefix: i32 = if (pane.file != null) panes.File.gutterWidth(pane) else 0;
-    const left = @max(0, @min(gesture.c0, gesture.c1));
-    const right = @max(0, @max(gesture.c0, gesture.c1));
     for (rows, 0..) |*row, index| {
         const visible = first + @as(i32, @intCast(index));
+        // A stream: only the first row starts where the press was; the
+        // others start after the line numbers, and all but the last run on.
+        const cols = sweepCols(gesture, visible + @as(i32, pane.tag_rows)).?;
+        const left: i32 = if (cols.first) cols.lo else prefix;
+        const right: i32 = cols.hi orelse std.math.maxInt(i32) / 2;
         var source = pane.wrapAt(visible);
         if (raw) source = .{ .line = panes.Terminal.gridOffset(pane) + visible, .at = 0 };
         const line = if (raw) modal.lineSlice(body, @intCast(visible)) else pointerSourceLine(pane, terminal_lines, source.line);
@@ -250,7 +253,8 @@ pub fn capturePointerSelection(p: *Pardes, pane: *Pane, slot: usize) !void {
         row.* = .{
             .row = source.line,
             .lo = lo,
-            .hi = if (right < prefix) lo else @min(end, modal.nextGrapheme(line, at)),
+            .hi = if (right < prefix) lo else if (cols.hi == null) end else @min(end, modal.nextGrapheme(line, at)),
+            .to_edge = cols.hi == null,
             .raw_terminal = raw,
             .prompt_bytes = if (raw) panes.Terminal.promptPrefixBytes(pane, source.line, line) else 0,
         };
@@ -294,40 +298,48 @@ pub fn selectionText(p: *Pardes, pane: *Pane, sl: Pane.Sel) ![]const u8 {
         }
         return result;
     }
-    const r0 = @min(sl.r0, sl.r1);
-    const r1 = @max(sl.r0, sl.r1);
-    const c0: usize = @intCast(@max(0, @min(sl.c0, sl.c1)));
-    const c1: usize = @intCast(@max(0, @max(sl.c0, sl.c1)));
     const text = try paneText(p, pane);
-    var total: usize = 0;
-    var selected: usize = 0;
-    var count_it = std.mem.splitAny(u8, text, "\n");
-    var count_row: i32 = 0;
-    while (count_it.next()) |line| : (count_row += 1) {
-        if (count_row < r0 or count_row > r1) continue;
-        const b0 = @min(panes.File.renderedLineByteCol(pane, count_row, line, c0), line.len);
-        const b1 = modal.nextGrapheme(line, @min(panes.File.renderedLineByteCol(pane, count_row, line, c1), line.len));
-        total += b1 - b0 + @intFromBool(selected > 0);
-        selected += 1;
-    }
-    const out = try arena.alloc(u8, total);
-    var at: usize = 0;
+    var out: std.ArrayList(u8) = .empty;
     var it = std.mem.splitAny(u8, text, "\n");
     var v: i32 = 0;
     var first = true;
     while (it.next()) |line| : (v += 1) {
-        if (v < r0 or v > r1) continue;
-        if (!first) {
-            out[at] = '\n';
-            at += 1;
-        }
+        const cols = sweepCols(sl, v) orelse continue;
+        if (!first) try out.append(arena, '\n');
         first = false;
-        const b0 = @min(panes.File.renderedLineByteCol(pane, v, line, c0), line.len);
-        const b1 = modal.nextGrapheme(line, @min(panes.File.renderedLineByteCol(pane, v, line, c1), line.len));
-        @memcpy(out[at..][0 .. b1 - b0], line[b0..b1]);
-        at += b1 - b0;
+        // Past the first row a body row starts after its line numbers.
+        const gutter: i32 = if (pane.file != null and v >= pane.tag_rows) panes.File.gutterWidth(pane) else 0;
+        const lo: usize = @intCast(if (cols.first) cols.lo else gutter);
+        const b0 = @min(panes.File.renderedLineByteCol(pane, v, line, lo), line.len);
+        const b1 = if (cols.hi) |hi|
+            @max(b0, modal.nextGrapheme(line, @min(panes.File.renderedLineByteCol(pane, v, line, @intCast(hi)), line.len)))
+        else
+            line.len;
+        try out.appendSlice(arena, line[b0..b1]);
     }
-    return out;
+    return out.items;
+}
+
+/// A sweep's columns on `row`, in its Sel space: acme's stream, not a
+/// rectangle (libframe/frselect.c:115-140, frselectpaint): the first row
+/// from the press to its end, the rows between whole, the last from its
+/// start to the release. `hi` null runs to the end of the row.
+pub const SweepCols = struct { lo: i32, hi: ?i32, first: bool };
+
+pub fn sweepCols(sl: Pane.Sel, row: i32) ?SweepCols {
+    const start, const end = sweepEnds(sl);
+    if (row < start[0] or row > end[0]) return null;
+    return .{
+        .lo = if (row == start[0]) @max(0, start[1]) else 0,
+        .hi = if (row == end[0]) @max(0, end[1]) else null,
+        .first = row == start[0],
+    };
+}
+
+/// The sweep's two ends in reading order, each (row, col).
+pub fn sweepEnds(sl: Pane.Sel) struct { [2]i32, [2]i32 } {
+    const fwd = sl.r0 < sl.r1 or (sl.r0 == sl.r1 and sl.c0 <= sl.c1);
+    return if (fwd) .{ .{ sl.r0, sl.c0 }, .{ sl.r1, sl.c1 } } else .{ .{ sl.r1, sl.c1 }, .{ sl.r0, sl.c0 } };
 }
 
 pub fn spanHas(r: i32, c: i32, ar: i32, ac: i32, br: i32, bc: i32) bool {
diff --git a/src/mouse.zig b/src/mouse.zig
index 22eb3270..2dcd80ed 100644
--- a/src/mouse.zig
+++ b/src/mouse.zig
@@ -691,12 +691,13 @@ fn gestureRange(p: *Pardes, id: usize, text: []const u8, on_tag: bool, operand:
     const start: ?modal.Cursor = if (operand.file_word) |w|
         .{ .row = @intCast(@max(0, w.row)), .col = @intCast(@max(0, w.lo)) }
     else if (operand.expanded orelse operand.preview) |sel| lead: {
-        // A selection's leading corner in reading order, converted the way
+        // A selection's start in reading order, converted the way
         // `pointerOperand` converts the click itself.
-        const top = @min(sel.r0, sel.r1) - @as(i32, pane.tag_rows);
+        const lead = edit.sweepEnds(sel)[0];
+        const top = lead[0] - @as(i32, pane.tag_rows);
         if (top < 0) break :lead null;
         const w = pane.wrapAt(top);
-        const col = edit.paneByteAtDisplay(p, &pane.body, w.line, w.at, @min(sel.c0, sel.c1) - panes.File.gutterWidth(pane));
+        const col = edit.paneByteAtDisplay(p, &pane.body, w.line, w.at, lead[1] - panes.File.gutterWidth(pane));
         break :lead .{
             .row = @intCast(@max(0, w.line)),
             .col = @intCast(@max(0, col)),
@@ -730,10 +731,11 @@ fn mirrorTtySelection(p: *Pardes, pane: *Pane) void {
     const rows = pane.pointerSelection(gesture) orelse return;
     const text = pane.rawPointerText(gesture) orelse return;
     if (rows.len == 0) return;
-    const endpoint = rows[if (gesture.r1 >= gesture.r0) rows.len - 1 else 0];
+    const forward = gesture.r1 > gesture.r0 or (gesture.r1 == gesture.r0 and gesture.c1 >= gesture.c0);
+    const endpoint = rows[if (forward) rows.len - 1 else 0];
     const body = body_layer.bodyText(p, p.scratch.allocator(), pane) catch return;
     const line = modal.lineSlice(body, @intCast(@max(0, endpoint.row - panes.Terminal.gridOffset(pane))));
-    const byte = if (gesture.c1 >= gesture.c0) modal.prevGrapheme(line, @min(endpoint.hi, line.len)) else endpoint.lo;
+    const byte = if (forward) modal.prevGrapheme(line, @min(endpoint.hi, line.len)) else endpoint.lo;
     pane.body.cur_row = pane.surfRow(endpoint.row);
     var shown = std.mem.trimEnd(u8, line[@min(endpoint.prompt_bytes, line.len)..], " \t");
     if (pane.ovl) |overlay| {
diff --git a/src/panes.zig b/src/panes.zig
index a7e5c668..e4621311 100644
--- a/src/panes.zig
+++ b/src/panes.zig
@@ -27,8 +27,10 @@ pub const Pane = struct {
     /// The words that throw unsaved text away (builtins.zig warnModified).
     pub const Discarding = enum { Exit, Restore, get };
 
-    /// One mouse selection (block-shaped), per button. c/r are text-area relative;
-    /// r counts from the tag's first row (the body starts at Pane.tag_rows).
+    /// One mouse sweep, per button: the press (c0, r0) and where it is now
+    /// (c1, r1), a stream between them as acme's (edit.sweepCols). c/r are
+    /// text-area relative; r counts from the tag's first row (the body
+    /// starts at Pane.tag_rows).
     pub const Sel = struct {
         state: enum { none, dragging, done } = .none,
         source_id: u64 = 0,
@@ -38,12 +40,15 @@ pub const Pane = struct {
         r1: i32 = 0,
     };
 
-    /// A rectangle keeps one source span per rendered row. Wrapped segments
-    /// remain separate rows when copied, even when they share a source line.
+    /// A captured sweep keeps one source span per rendered row. Wrapped
+    /// segments remain separate rows when copied, even when they share a
+    /// source line.
     pub const PointerRow = struct {
         row: i32,
         lo: usize,
         hi: usize,
+        /// Not the sweep's last row: its highlight runs to the right edge.
+        to_edge: bool = false,
         prefix: [32]u8 = @splat(0),
         prefix_len: u8 = 0,
         raw_terminal: bool = false,