Add the first component and three surfaces

Vega reads a verified Pure module by convention: a table view with a
label column is a list (with optional badge, detail and tone), any other
table is a table, <table>_focus is its focused row, a title view is the
title and other views are fields. lib/vega.aup gives aup apps the tones,
which say what a row means; each surface decides how it looks or sounds.

vega tui draws the screen in a terminal, keeps the focused row in view
and evaluates only the cells on screen; vega cli prints plain lines for
pipes; vega say speaks the screen and each focus change as sentences.
Display width handles Hangul, CJK, emoji, combining marks and controls.

tests/check.py compares the CLI and NUI output with a reference model of
examples/todo.aup line for line, checks 9,600 TUI frames for scrolling,
focus, badge alignment and the number of cells evaluated, drives the
interactive TUI on a pseudo-terminal, and runs every aup example on every
surface.

1 files changed, 40 insertions, 0 deletions

diff --git a/examples/todo.aup b/examples/todo.aup
new file mode 100644
index 0000000..a5ee3b0
--- /dev/null
+++ b/examples/todo.aup
@@ -0,0 +1,40 @@
+# A to-do list as Vega reads it: one spec, shown by the terminal (vega tui),
+# printed for pipes (vega cli) and spoken as sentences (vega say).
+use vega
+
+record Task {
+  title: text
+  done = 0
+  urgent = 0
+}
+
+state tasks: list of Task
+state at: index of tasks
+
+input add = text
+input up = key ArrowUp
+input down = key ArrowDown
+input toggle = key Space
+input urgent = key KeyU
+input drop = key Delete
+
+on add {
+  tasks.append(Task { title: add })
+  at = tasks.last
+}
+on up.down { at = at - 1 }
+on down.down { at = at + 1 }
+on toggle.down { at.done = !at.done }
+on urgent.down { at.urgent = !at.urgent }
+on drop.down { tasks.remove(at) }
+
+view title = "To do"
+view left = "{tasks.count} tasks"
+
+# A list: label, and optionally tone, badge and detail per row.
+view tasks_list = each task in tasks {
+  label = task.title
+  badge = if task.done { "done" } else if task.urgent { "urgent" } else { "" }
+  tone = if task.done { vega.muted } else { vega.when(task.urgent, vega.danger) }
+}
+view tasks_list_focus = at.position