Scroll a tag taller than its rows to keep its caret in view

A tag shows at most eight rows, so a longer one (a 9P write of many lines, or
`o` in the tag) put its caret on a line that was never drawn. Pane, column and
workspace tags now keep a first line on screen that follows the caret while
they have the keyboard, and the pointer and the pane text count their rows
from it.

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

1 files changed, 60 insertions, 0 deletions

diff --git a/test/panes.zig b/test/panes.zig
index 954e431b..9b800430 100644
--- a/test/panes.zig
+++ b/test/panes.zig
@@ -228,6 +228,66 @@ test "a tag with a newline in it is as tall as its lines, and each line is typed
     }
 }
 
+test "a tag with more lines than rows scrolls to keep its caret in view" {
+    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .cols = 80, .rows = 30 });
+    defer p.deinit();
+    const pane = try p.setTestFile("body\n");
+    p.presentation.enabled = false;
+    var many: std.ArrayList(u8) = .empty;
+    defer many.deinit(std.testing.allocator);
+    for (1..21) |n| try many.print(std.testing.allocator, "\nL{d}", .{n});
+    try pane.appendTag(many.items);
+    p.update(.tick);
+    try std.testing.expectEqual(@as(u16, pardes.MAX_TAG_ROWS), pane.tag_rows);
+    var frame = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer frame.deinit();
+    const r = p.rects[0];
+    const x = r.x + pardes.TAG_TEXT_INSET;
+    // To the last line: the tag scrolls so it is the bottom row, caret on it.
+    p.update(.{ .key = .{ .cp = ':' } });
+    p.update(.{ .key = .{ .cp = 'g' } });
+    p.update(.{ .key = .{ .cp = 'e' } });
+    try std.testing.expectEqual(@as(i32, 20), pane.tag.cur_row);
+    const bottom = try p.render(frame.allocator());
+    const tag_y = p.tagTop(pane, r);
+    const last_row = tag_y + pardes.MAX_TAG_ROWS - 1;
+    try std.testing.expectEqual(last_row, bottom.cursor.?.y);
+    try std.testing.expectEqualStrings("L", bottom.at(x, last_row).grapheme());
+    try std.testing.expectEqualStrings("2", bottom.at(x + 1, last_row).grapheme());
+    try std.testing.expectEqualStrings("0", bottom.at(x + 2, last_row).grapheme());
+    // what the pointer sees is what is shown: its first row is line 13
+    const text = try pardes.edit.paneText(p, pane);
+    try std.testing.expectEqualStrings("L13", modal.lineSlice(text, 0));
+    ClickCursorTests.click(p, .left, x + 1, tag_y + 1);
+    try std.testing.expectEqual(@as(i32, 14), pane.tag.cur_row);
+    try std.testing.expectEqual(@as(i32, 1), pane.tag.cur_col);
+    // Back to the first line brings the prefix back into view.
+    p.update(.{ .key = .{ .cp = Key.escape } });
+    p.update(.{ .key = .{ .cp = 'g' } });
+    p.update(.{ .key = .{ .cp = 'g' } });
+    const top = try p.render(frame.allocator());
+    try std.testing.expectEqual(@as(u16, 0), pane.tag_top);
+    try std.testing.expectEqual(tag_y, top.cursor.?.y);
+    try std.testing.expectEqualStrings("/", top.at(x, tag_y).grapheme());
+
+    // A column tag does the same in its rows.
+    many.clearRetainingCapacity();
+    try many.appendSlice(std.testing.allocator, "New");
+    for (1..21) |n| try many.print(std.testing.allocator, "\nC{d}", .{n});
+    p.col_tags[0].own = try p.gpa.dupe(u8, many.items);
+    p.update(.tick);
+    const rows = p.columnBarHeight();
+    try std.testing.expectEqual(@as(u16, pardes.MAX_TAG_ROWS), rows);
+    pardes.tagline.enterHeader(p, 0);
+    p.update(.{ .key = .{ .cp = 'g' } });
+    p.update(.{ .key = .{ .cp = 'e' } });
+    const header = try p.render(frame.allocator());
+    const header_row = p.topBarHeight() + rows - 1;
+    try std.testing.expectEqual(header_row, header.cursor.?.y);
+    try std.testing.expectEqualStrings("C", header.at(p.col_x[0] + pardes.TAG_TEXT_INSET, header_row).grapheme());
+    try std.testing.expectEqualStrings("2", header.at(p.col_x[0] + pardes.TAG_TEXT_INSET + 1, header_row).grapheme());
+}
+
 const TagNavigationTests = struct {
     fn key(p: *Pardes, cp: u21) void {
         p.update(.{ .key = .{ .cp = cp } });