A pane whose whole text fits in its rows never scrolls to keep a margin

The scroll margin reveals text; with none off screen there is nothing to
reveal. ensureCursorVisible and a centred look both leave such a pane at its
top. A longer file keeps helix's clamp (hxdiff and hxparity unchanged).

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

8 files changed, 56 insertions, 78 deletions

diff --git a/src/look.zig b/src/look.zig
index b6a89b64..a413bf50 100644
--- a/src/look.zig
+++ b/src/look.zig
@@ -968,7 +968,8 @@ pub fn focusPaneLine(p: *Pardes, id: usize, at: Spot, landing: enum { center, ke
     if (pane.file) |*f| {
         if (at.line > panes.File.nlines(p.gpa, f)) return;
         if (landing == .center) {
-            const next = (at.line - 1) -| pane.rows / 2; // center, clamp at top
+            // center, clamp at top; a text that fits is shown whole
+            const next = if (pane.textFits()) 0 else (at.line - 1) -| pane.rows / 2;
             if (next != f.scroll) {
                 f.scroll = next;
                 f.syntax_dirty = true;
diff --git a/src/panes.zig b/src/panes.zig
index a7e5c668..47582692 100644
--- a/src/panes.zig
+++ b/src/panes.zig
@@ -512,6 +512,16 @@ 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 +549,13 @@ 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)));
diff --git a/src/pardes.zig b/src/pardes.zig
index 23341904..18eedccb 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -1354,6 +1354,24 @@ test "BootShell keep leaves the untouched boot shell a dragged document joins; r
     }
 }
 
+test "a pane its whole text fits in never scrolls to keep a margin" {
+    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 30 });
+    defer p.deinit();
+    const pane = try p.setTestFile("one\ntwo\nthree\n");
+    // A second pane under it, as acme's placement puts one: right under the
+    // three lines, which leaves the file exactly three body rows.
+    const below = p.freeSlot().?;
+    _ = try p.openTutorView(below);
+    exec.placeNew(p, 0, 0, below, .doc);
+    p.active = 0;
+    p.sync();
+    try std.testing.expectEqual(@as(u16, 3), p.rects[0].h - pane.tag_rows);
+    for ("jj") |c| p.update(.{ .key = .{ .cp = c, .text = &.{c} } });
+    p.sync();
+    try std.testing.expectEqual(@as(i32, 2), pane.body.cur_row);
+    try std.testing.expectEqual(@as(i32, 0), pane.scroll());
+}
+
 test "dragging a column's only pane to another leaves that column in place, empty" {
     const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 160, .rows = 32 });
     defer p.deinit();
diff --git a/test/snapshots/find.golden b/test/snapshots/find.golden
index 50557fad..e6e1bac1 100644
--- a/test/snapshots/find.golden
+++ b/test/snapshots/find.golden
@@ -65,15 +65,9 @@
 |12:    /tmp/pardes-snap/find/cwd/sub/nest/zqmark-gamma.txt Save Tty Collapse Del
 |13:      1 gamma body
 == snap third grid=120x41 cursor=7,16
-|6:      2 sub/nest/zqmark-gamma.txt
-|7:      3 zqmark-alpha.txt
-|8:      4
 |15:    /tmp/pardes-snap/find/cwd/zqmark-alpha.txt Save Tty Collapse Del
 |16:      1 alpha body
 == snap back grid=120x41 cursor=7,13
-|6:      1 sub/ZQMARK-beta.txt
-|7:      2 sub/nest/zqmark-gamma.txt
-|8:      3 zqmark-alpha.txt
 == snap word grid=120x41 cursor=7,13
 |3:      1 Find                                                                                                        Find
 |4:                                                                                                                  Find /
@@ -81,11 +75,8 @@
 |3:      1 Find                                                                                                      Find /
 |4:
 |13:      1 gamma body                                                                                                  Last
-== snap nomatch grid=120x41 cursor=7,7
+== snap nomatch grid=120x41 cursor=7,8
 |3:      1 Find
-|6:      2 sub/nest/zqmark-gamma.txt
-|7:      3 zqmark-alpha.txt
-|8:      4
 |13:      1 gamma body
 |18:    /tmp/pardes-snap/find/cwd/+Search Save Tty Collapse Del
 |19:      1
diff --git a/test/snapshots/lookrange.golden b/test/snapshots/lookrange.golden
index 19a83f2c..7d802b0b 100644
--- a/test/snapshots/lookrange.golden
+++ b/test/snapshots/lookrange.golden
@@ -85,37 +85,11 @@
 |19: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-9 #e5eee5,#0d1410, 10-15 #f7e4a5,#5e4923, 16-18 #e5eee5,#0d1410, 19-149 d,#0d1410,
 |20: 0-0 d,#608269, 1-1 d,#0d1410, 2-18 #59675c,#0d1410, 19-149 d,#0d1410,
 |21: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-11 #e5eee5,#0d1410, 12-17 #f7e4a5,#5e4923, 18-149 d,#0d1410,
-== snap hit2 grid=150x31 cursor=17,12
-|8:      4 dddd
-|9:      5 eeee
-|10:      6 ffff
-|11:      7 gg NEEDLE gg
-|12:      8 hhhh NEEDLE
-|13:      9 iiii
-|14:
-|15:
-|16:
+== snap hit2 grid=150x31 cursor=17,15
 == style hit2 grid=150x31
-|8: 0-0 d,#152019, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-10 #e5eee5,#0d1410, 11-149 d,#0d1410,
-|9: 0-0 d,#152019, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-10 #e5eee5,#0d1410, 11-149 d,#0d1410,
-|10: 0-0 d,#152019, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-10 #e5eee5,#0d1410, 11-149 d,#0d1410,
-|11: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-18 #e5eee5,#0d1410, 19-149 d,#0d1410,
-|12: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #616f64,#0d1410,b 7-11 #e5eee5,#0d1410, 12-17 #f5f7ee,#3c614a, 18-149 d,#0d1410,
-|14: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-149 d,#0d1410,
-|15: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-149 d,#0d1410,
-|16: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-149 d,#0d1410,
-== snap back grid=150x31 cursor=15,12
-|8:      3 cccc dccc
-|9:      4 dddd
-|10:      5 eeee
-|11:      6 ffff
-|12:      7 gg NEEDLE gg
-|13:      8 hhhh NEEDLE
-|14:      9 iiii
+|14: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-18 #e5eee5,#0d1410, 19-149 d,#0d1410,
+|15: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #616f64,#0d1410,b 7-11 #e5eee5,#0d1410, 12-17 #f5f7ee,#3c614a, 18-149 d,#0d1410,
+== snap back grid=150x31 cursor=15,14
 == style back grid=150x31
-|8: 0-0 d,#152019, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-15 #e5eee5,#0d1410, 16-149 d,#0d1410,
-|10: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-10 #e5eee5,#0d1410, 11-149 d,#0d1410,
-|11: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-10 #e5eee5,#0d1410, 11-149 d,#0d1410,
-|12: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #616f64,#0d1410,b 7-9 #e5eee5,#0d1410, 10-15 #f5f7ee,#3c614a, 16-18 #e5eee5,#0d1410, 19-149 d,#0d1410,
-|13: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-17 #e5eee5,#0d1410, 18-149 d,#0d1410,
-|14: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-10 #e5eee5,#0d1410, 11-149 d,#0d1410,
+|14: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #616f64,#0d1410,b 7-9 #e5eee5,#0d1410, 10-15 #f5f7ee,#3c614a, 16-18 #e5eee5,#0d1410, 19-149 d,#0d1410,
+|15: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-17 #e5eee5,#0d1410, 18-149 d,#0d1410,
diff --git a/test/snapshots/lsp-client.golden b/test/snapshots/lsp-client.golden
index e4ea4c90..17eb0d40 100644
--- a/test/snapshots/lsp-client.golden
+++ b/test/snapshots/lsp-client.golden
@@ -25,19 +25,5 @@
 |20:      5 main.rs:5:13-15
 |21:      6     let y = add(3, 4);
 |22:      7
-== snap gr-opened grid=100x25 cursor=21,6
-|3:      2
-|4:      3 fn main() {
-|5:      4     let x = add(1, 2);
-|6:      5     let y = add(3, 4);
-|7:      6     let _ = x + y;
-|8:      7 }
-|9:      8
+== snap gr-opened grid=100x25 cursor=21,7
 == snap gr-back grid=100x25 cursor=21,6
-|3:      1 mod lib;
-|4:      2
-|5:      3 fn main() {
-|6:      4     let x = add(1, 2);
-|7:      5     let y = add(3, 4);
-|8:      6     let _ = x + y;
-|9:      7 }
diff --git a/test/snapshots/rsearch.golden b/test/snapshots/rsearch.golden
index 6e078612..872693bb 100644
--- a/test/snapshots/rsearch.golden
+++ b/test/snapshots/rsearch.golden
@@ -17,17 +17,14 @@
 |14:      3 code.txt:3:1-7
 |15:      4 count_x again
 |16:      5
-== snap select grid=210x31 cursor=14,9
-|7:      2 open sub/dep.txt:3 here
-|8:      3 count_x again
-|9:      4 pick two words
+== snap select grid=210x31 cursor=14,10
 |10: ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
 |16:    /tmp/pardes-snap/rsearch/cwd/+Search Save Tty Collapse Del LocationsConfig
 |17:      1 code.txt:4:1-8
 |18:      2 pick two words
 |19:      3
 == snap path-open grid=210x31 cursor=7,22
-|10:
+|10:      4 pick two words
 |19:    /tmp/pardes-snap/rsearch/cwd/sub/dep.txt Save Tty Collapse Del
 |20:      1 d1
 |21:      2 d2
@@ -36,10 +33,6 @@
 |24:      5 d5
 |25:      6 d6
 == snap step1 grid=210x31 cursor=13,9
-|7:      1 run count_x now
-|8:      2 open sub/dep.txt:3 here
-|9:      3 count_x again
-|10:      4 pick two words
 == snap step2 grid=210x31 cursor=13,9
 == snap step3 grid=210x31 cursor=13,9
 == snap selclick grid=210x31 cursor=14,10
diff --git a/test/snapshots/rsearch.snap b/test/snapshots/rsearch.snap
index d880e557..0ce257bd 100644
--- a/test/snapshots/rsearch.snap
+++ b/test/snapshots/rsearch.snap
@@ -50,17 +50,16 @@ snap select
 # right-CLICK the path `sub/dep.txt:3` (line 2, col 18): isFileChar keeps / . :
 # so the click expands the whole token and it RESOLVES — a look, not a search —
 # opening dep.txt scrolled to line 3 (DEPTARGET). The "don't break paths" case.
-press right 18 8
-release right 18 8
+press right 18 9
+release right 18 9
 wait 10000 DEPTARGET
 stable 700 15000
 snap path-open
 # A click does not merely LIST the hits, it goes to one: this re-search of
-# `count_x` (line 3, col 12: acme sized code.txt to its four lines, and the
-# first search scrolled line 1 off) also STEPS onto hit 1, so the cursor lands
-# in the match, not where the click was.
-press right 12 9
-release right 12 9
+# `count_x` (line 1, col 15) also STEPS onto hit 1, so the cursor lands in the
+# match, not where the click was.
+press right 15 8
+release right 15 8
 stable 700 15000
 snap step1
 # ...and the same word clicked in its OTHER place (line 3, col 10) opens NO
@@ -75,9 +74,9 @@ press right 10 10
 release right 10 10
 stable 700 15000
 snap step3
-# acme sized code.txt to its four lines, and on so tight a pane a click on
-# line 4 scrolls it to keep its context rows: drag its last row (the resize
-# handle) down four rows first, so the rows below stay where they are clicked.
+# acme sized code.txt to its four lines, so line 4 is on its last row, and a
+# pane's last row is its resize handle: a press there would drag the seam, not
+# sweep text. Drag that handle down four rows first.
 press left 40 11
 drag left 40 15
 release left 40 15