fix: restore the line width card.ring sets, add card.truncate

A ring left its line width behind, so the next stroke on the card inherited
a hairline several pixels thick. It already restored the cap for the same
reason.

card.truncate replaces byte slicing, which cuts a multi-byte character in
half and emits an invalid sequence Cairo draws as a box.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/lib/card.lua b/lib/card.lua
index c83e6bc..f25c393 100644
--- a/lib/card.lua
+++ b/lib/card.lua
@@ -188,6 +188,7 @@ function M.ring(cr, cx, cy, r, frac, colour, colors, width)
   -- and cairo_arc() joins to it with a straight line, so without this every
   -- ring after a label is drawn with a stray chord to the text baseline.
   cairo_new_path(cr)
+  local prev_width = cairo_get_line_width(cr)
   cairo_set_line_width(cr, width)
   cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND)
 
@@ -200,9 +201,11 @@ function M.ring(cr, cx, cy, r, frac, colour, colors, width)
     cairo_arc(cr, cx, cy, r, -math.pi / 2, -math.pi / 2 + math.pi * 2 * frac)
     cairo_stroke(cr)
   end
-  -- Leave the cap as it was found: a later stroke inheriting ROUND would get
-  -- visibly rounded ends on the card's hairlines.
+  -- Leave the line state as it was found. A later stroke inheriting ROUND gets
+  -- visibly rounded ends on the card's hairlines, and one inheriting this
+  -- width gets a hairline several pixels thick.
   cairo_set_line_cap(cr, CAIRO_LINE_CAP_BUTT)
+  cairo_set_line_width(cr, prev_width)
 end
 
 -- The largest base size S at which every row of pieces still fits max_w,
@@ -246,4 +249,25 @@ function M.human(bytes)
   return string.format('%.1f%s', n, units[i])
 end
 
+-- Shorten a string to `limit` characters, appending an ellipsis when it cuts.
+--
+-- By character, never by byte: Lua's string.sub counts bytes, so slicing a
+-- UTF-8 name mid-sequence emits an invalid byte, which Cairo draws as a
+-- replacement box. A name long enough to need shortening is exactly the kind
+-- likely to carry an accent.
+--
+-- This counts codepoints, not rendered width, so it does not account for a
+-- double-width CJK glyph. That is the right trade here: the strings it cuts
+-- are cache directory names and hardware model strings. Measure with
+-- M.measure when true rendered width matters.
+function M.truncate(s, limit)
+  s = tostring(s or '')
+  limit = tonumber(limit) or 0
+  if limit <= 0 then return '' end
+  if utf8.len(s) == nil then return s:sub(1, limit) end  -- not valid UTF-8: byte-slice
+  if utf8.len(s) <= limit then return s end
+  local cut = utf8.offset(s, limit)  -- byte index of the limit'th character
+  return s:sub(1, cut - 1) .. '\u{2026}'
+end
+
 return M