1 files changed, 32 insertions, 6 deletions

diff --git a/src/panes.zig b/src/panes.zig
index 8049da4e..8ca2bb4d 100644
--- a/src/panes.zig
+++ b/src/panes.zig
@@ -25,10 +25,12 @@ pub const EditText = struct { text: []u8, row0: i32 };
 
 pub const Pane = struct {
     /// The words that throw unsaved text away (builtins.zig warnModified).
-    pub const Discarding = enum { Exit, Restore };
+    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,
@@ -181,6 +186,11 @@ pub const Pane = struct {
     /// scrolls to keep its caret in view while it has the keyboard; pointer
     /// rows count from this line, not the tag's first.
     tag_top: u16 = 0,
+    /// The tag shows all its rows (acme's `tagexpand`, on by default); off,
+    /// one row, as acme's Tagup leaves it. Down on the
+    /// tag's last line and Up on its first, typing, or Alt-Down and Alt-Up
+    /// in the tag, as acme's arrows in a tag (plan9port text.c:776).
+    tag_expanded: bool = true,
     /// How long the tag's computed prefix was when its positions were last
     /// placed. They count from the start of the prefix, so when it grows or
     /// shrinks (a rename, the dirty marker, a PDF's page) what follows it
@@ -512,6 +522,16 @@ pub const Pane = struct {
         }
     }
 
+    /// Every line of the file's text fits in the body's rows; the empty
+    /// line after a final newline is no text.
+    pub fn textFits(pane: *Pane) bool {
+        if (pane.file) |*f| {
+            const lines = File.nlines(pane.gpa, f) - @intFromBool(std.mem.endsWith(u8, f.content, "\n"));
+            return lines <= pane.rows;
+        }
+        return false;
+    }
+
     pub fn ensureCursorVisible(pane: *Pane) void {
         const off = pane.scroll();
         var in_context = false;
@@ -539,7 +559,13 @@ pub const Pane = struct {
                 pane.scrollBy(pane.body.cur_row - margin - off);
             } else if (pane.body.cur_row > last - margin) {
                 var to = pane.body.cur_row + margin;
-                if (pane.file) |*f| to = @min(to, @as(i32, @intCast(File.nlines(pane.gpa, f) -| 1)));
+                if (pane.file) |*f| {
+                    // The margin only reveals text: a pane its whole text
+                    // fits in never scrolls for it. A longer one keeps
+                    // helix's clamp at the buffer's last line.
+                    const lines: i32 = @intCast(File.nlines(pane.gpa, f));
+                    to = @min(to, if (off == 0 and pane.textFits()) @max(pane.body.cur_row, lines - 1 - @intFromBool(std.mem.endsWith(u8, f.content, "\n"))) else lines - 1);
+                }
                 if (comptime Pdf.enabled) {
                     if (pane.pdf) |pv|
                         to = @min(to, @as(i32, @intCast(modal.lineCount(pv.text) -| 1)));