tryst-spinner

An indeterminate activity ring and determinate progress ring for tryst, Crystal's Tcl/Tk binding. An antialiased stroke with round caps is the whole visual point: Tk's own indeterminate ttk::progressbar has neither. Built on Tryst::OwnerDrawnWidget (see CUSTOM_WIDGETS.md if you're building your own widget rather than just using this one).

require "tryst"
require "tryst-spinner"

app = Tryst::App.new

spinner = Tryst::Spinner.new(app)              # indeterminate by default
spinner.pack

sync = Tryst::Spinner.new(app, value: 0.0, show_value: true) # determinate
sync.pack
sync.value = 0.65                              # 65%, animates there smoothly

app.show
app.mainloop

It's just a widget: #pack/#grid place it, #value/#value= read and set it. #value = nil (the default) is indeterminate — a continuously rotating arc whose own length breathes, not a fixed wedge just spinning in place. #value = a_float (clamped to [0.0, 1.0]) is determinate — a fixed arc from 12 o'clock to that fraction of the ring. Determinate mode isn't a separate widget: it's just what happens when #value stops being nil. Going from one determinate value to another animates smoothly (200ms, eased); the very first determinate value, or one arriving right after a stretch of indeterminate, jumps straight there — there's no meaningful position to animate from in either case. See examples/spinner_demo.cr for a runnable version: two indeterminate sizes, one driven by a repeating timer standing in for real progress reports, and one that switches from indeterminate to a fixed value at runtime.

It's purely a display widget — no click/keyboard handling, and it's not in Tab order (a real ttk::progressbar isn't focusable either).

size: and thickness: are both in logical pixels (thickness: defaults to roughly 12% of size: if not given); accent: overrides the theme-derived color with a #rrggbb hex string, same convention as tryst-value-slider's own accent:. show_value: draws a centered percentage (only ever visible in determinate mode); font: controls that label's font ("TkDefaultFont" by default — any real Tk font spec works).

One indeterminate spinner running costs roughly +4% of one CPU core at idle (measured on an M-series Mac); each additional one on screen adds about the same again, since none of them share redraw work.

Requirements

Whatever tryst and tryst-vector need — Crystal >= 1.21.0, Tcl/Tk 8.6, and ThorVG >= 1.0 (see tryst-vector's own README for per-platform package names and why).

Examples

crystal run examples/spinner_demo.cr

Tests

shards install
crystal spec                    # host
scripts/docker-test.sh          # Debian forky, same suite

scripts/docker-test.sh builds from this repo's own root; shards install inside the image fetches tryst and tryst-vector directly via their github: dependencies. It takes the same arguments crystal spec does, so a focused run works there too.