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, 10 insertions, 6 deletions

diff --git a/src/mouse.zig b/src/mouse.zig
index df657ead..69feea29 100644
--- a/src/mouse.zig
+++ b/src/mouse.zig
@@ -276,10 +276,13 @@ pub fn handleMouse(p: *Pardes, m: Mouse) void {
         };
         const x = if (p.header_column) |c| p.col_x[c] + TAG_TEXT_INSET else 0;
         const text = edit.flatSurface(p, t) catch return;
-        const top = if (p.header_column != null) p.topBarHeight() else 0;
-        const line: u16 = @intCast(@min(mrow -| top, modal.lineCount(text) -| 1, (if (p.header_column != null) p.columnBarHeight() else p.topBarHeight()) -| 1));
+        // `row` is the header's row on screen, `line` the line of its text
+        // shown there.
+        const base = if (p.header_column != null) p.topBarHeight() else 0;
+        const row: u16 = @intCast(@min(mrow -| base, (if (p.header_column != null) p.columnBarHeight() else p.topBarHeight()) -| 1));
+        const line: u16 = @intCast(@min(row + p.header_top, modal.lineCount(text) -| 1));
         const bar = modal.lineSlice(text, line);
-        const at = @min(bar.len, panes.File.rawAtDisplay(bar, (tag_layer.columnAt(p, if (p.header_column != null) .column else .workspace, p.header_column orelse 0, p.pointer_tag_hit, p.header_drag, line) orelse (mcol -| x)) + p.header_scroll));
+        const at = @min(bar.len, panes.File.rawAtDisplay(bar, (tag_layer.columnAt(p, if (p.header_column != null) .column else .workspace, p.header_column orelse 0, p.pointer_tag_hit, p.header_drag, row) orelse (mcol -| x)) + p.header_scroll));
         // the anchor stays where the press put it
         t.cur_row = line;
         t.cur_col = @intCast(at);
@@ -310,11 +313,12 @@ pub fn handleMouse(p: *Pardes, m: Mouse) void {
         const t = if (column) |c| &p.col_tags[c] else &p.global_tag;
         const focused = p.header_focus and p.header_column == column;
         const text = edit.flatSurface(p, t) catch return;
-        const line: u16 = @intCast(mrow - if (column != null) p.topBarHeight() else 0);
+        const row: u16 = @intCast(mrow - if (column != null) p.topBarHeight() else 0);
+        const line: u16 = @intCast(row + if (focused) p.header_top else 0);
         if (line > 0 and line >= modal.lineCount(text)) return;
         const bar = modal.lineSlice(text, line);
         const scroll = if (focused) p.header_scroll else 0;
-        const at = @min(bar.len, panes.File.rawAtDisplay(bar, (tag_layer.columnAt(p, if (column != null) .column else .workspace, column orelse 0, p.pointer_tag_hit, p.header_drag, line) orelse (mcol -| x)) + scroll));
+        const at = @min(bar.len, panes.File.rawAtDisplay(bar, (tag_layer.columnAt(p, if (column != null) .column else .workspace, column orelse 0, p.pointer_tag_hit, p.header_drag, row) orelse (mcol -| x)) + scroll));
         if (m.button == config.select_button) {
             // A clicked header is typed straight into, as a clicked tag is.
             if (!focused) tagline.enterHeader(p, column);
@@ -662,7 +666,7 @@ fn gestureRange(p: *Pardes, id: usize, text: []const u8, on_tag: bool, operand:
         const tag = tagline.tagText(p, p.scratch.allocator(), pane) catch return .{};
         const sel = operand.expanded orelse operand.preview orelse return .{};
         const lead = if (sel.r0 < sel.r1 or (sel.r0 == sel.r1 and sel.c0 <= sel.c1)) sel else Pane.Sel{ .r0 = sel.r1, .c0 = sel.c1 };
-        const row: usize = @intCast(@max(0, lead.r0));
+        const row: usize = @as(usize, @intCast(@max(0, lead.r0))) + pane.tag_top;
         const start = modal.lineStartOffset(tag, row);
         const at = start + panes.File.rawAtDisplay(modal.lineSlice(tag, row), @intCast(@max(0, lead.c0)));
         const q0: u32 = @intCast(@min(at, tag.len));