feat: add the disks and cache cards

disks draws a ring per filesystem from the df sample, with the NFS
server address read from the device field and a labelled-bar fallback
when the rings would be too small to read. cache shows the ~/.cache
total and its four largest children from the du sample.

card.ring now resets the cairo path first: a preceding card.text()
leaves a current point, and cairo_arc() joins to it with a straight
line, so the disks rings were drawn with stray chords. The ring
primitive had no caller until now, which is why it went unnoticed.

1 files changed, 63 insertions, 0 deletions

diff --git a/widgets/cache.lua b/widgets/cache.lua
new file mode 100644
index 0000000..a1a42e3
--- /dev/null
+++ b/widgets/cache.lua
@@ -0,0 +1,63 @@
+-- Cache: ~/.cache total and its four largest subdirectories.
+--
+-- Reads a cache file written by bin/cache-sample.sh. du walks the tree and
+-- costs about 100ms, which cannot happen on a 2-second draw.
+
+local card = require 'lib.card'
+local data = require 'lib.data'
+
+local CACHE = (os.getenv('XDG_CACHE_HOME') or (os.getenv('HOME') .. '/.cache'))
+  .. '/udt/cachesize.txt'
+
+local M = {}
+
+function M.draw(cr, rect, colors)
+  local inner = card.card(cr, rect, colors)
+  local function clamp(v, lo, hi) return math.max(lo, math.min(hi, v)) end
+  local label_size = clamp(inner.w * 0.030, 10, 16)
+  local big_size   = clamp(inner.w * 0.075, 22, 46)
+
+  card.font(cr, card.FONT_MONO, label_size, false)
+  card.rgba(cr, colors.label)
+  card.text(cr, inner.x, inner.y + label_size, 'CACHE')
+
+  local c = data.du_parse(data.slurp(CACHE) or '')
+  if not c then
+    card.rgba(cr, colors.label)
+    card.font(cr, card.FONT_UI, label_size * 1.2, true)
+    card.text(cr, inner.x, inner.y + label_size * 3.4, 'no cache data')
+    card.font(cr, card.FONT_MONO, label_size, false)
+    card.text(cr, inner.x, inner.y + label_size * 5, 'bin/cache-sample.sh')
+    return
+  end
+
+  card.font(cr, card.FONT_HEAVY, big_size, false)
+  card.rgba(cr, colors.body)
+  card.text(cr, inner.x, inner.y + label_size + big_size, c.total.label)
+
+  local ey = inner.y + label_size + big_size + label_size * 2
+  local step = label_size * 2.2
+
+  card.font(cr, card.FONT_MONO, label_size, false)
+  for i, e in ipairs(c.items) do
+    if ey + step > inner.y + inner.h then break end
+    -- The biggest offender is the point of the card, so it carries colour:
+    -- critical when it is over half the total, warning otherwise. The rest
+    -- stay in the ordinary value colour so the eye lands on the one to delete.
+    local colour = colors.value
+    if i == 1 then
+      local share = c.total.bytes > 0 and (e.bytes / c.total.bytes) or 0
+      colour = share > 0.5 and colors.critical or colors.warning
+    end
+    card.rgba(cr, colors.label)
+    -- Long names are truncated rather than allowed to collide with the size.
+    local name = e.name
+    if #name > 18 then name = name:sub(1, 17) .. '\u{2026}' end
+    card.text(cr, inner.x, ey, name)
+    card.rgba(cr, colour)
+    card.text_right(cr, inner.x + inner.w, ey, e.label)
+    ey = ey + step
+  end
+end
+
+return M