Explicit standalone content constraints¶

ravet_webview::ContentConstraints is a portable, dependency-free value and size resolver. On macOS, StandaloneWindow::set_content_constraints installs that policy on the existing main-thread window owner. The policy is opt-in; window creation and the standard title-bar Audio/MIDI popup keep their existing defaults.

use ravet_webview::ContentConstraints;
let policy = ContentConstraints::new(640., 480., 1600., 1200.).unwrap();
assert_eq!(policy.resolve(320., 240., None), Some((640., 480.)));
assert_eq!(policy.resolve(1600., 1000., Some((4., 3.))),
           Some((4000. / 3., 1000.)));

Minimum and maximum widths must be finite values in 320..=4096 logical points; heights must be in 240..=4096, with minimum <= maximum on each axis. Bounds may be fractional or equal. Invalid construction returns None. The copied value has private fields and reports its bounds with minimum_size and maximum_size.

resolve(width, height, aspect) accepts any finite positive requested extent. Without an aspect it clamps each dimension independently. A finite positive aspect pair defines a common scale interval from both bounds. The resolver fits the largest matching rectangle within the request, then clamps its scale into that interval: an undersized request can grow to the minimum. Empty or unrepresentable scale intervals, invalid requests and invalid aspects return None. Final products are clamped to bounds to contain floating-point rounding. The function allocates nothing and has no native, threading or I/O dependency; it does not certify a real-time deadline or define display-pixel rounding.

Owned native installation¶

On an existing macOS StandaloneWindow, call set_content_constraints(Some(policy)). The wrapper reads actual content size, preflights compatibility with the window's original optional aspect ratio, installs native content minimum/maximum properties, and immediately requests the resolved extent. Invalid or incompatible proposals return false before any Rust/native policy or geometry write. Native installation widens the old maximum before setting the new minimum and final maximum, so a smaller replacement does not temporarily invert the admitted bounds.

content_constraints() returns the last admitted copied policy. Both installs and set_size reject synchronous reentry while either operation is in progress. A resize notification emitted during installation sees the prior admitted policy; the new value is published only after the native call succeeds. This prevents an older outer operation from overwriting a nested accepted policy. The main-thread owner, editor-before-parent borrowing and teardown remain in force. Once a native operation is admitted, arbitrary foreign Cocoa observer effects cannot be rolled back by RAVET.

After window close admission, policy installation and resize reject, content_size() returns None, and the last admitted copied policy remains readable. Close requests share the synchronous operation guard.

set_size retains its finite 320..=4096 by 240..=4096 request limits. An installed policy resolves those requests before native fitting. None restores the exact native user-resize content minimum/maximum captured at creation without making a new size request. Subsequent programmatic sizing follows the original no-policy behavior, including requests below the native user-resize minimum.

Native user constraints, programmatic requests and actual measurements are different observations. Cocoa can independently round dimensions to logical points: measured content may differ from policy bounds or the compatible aspect projection by up to one point. Read content_size() after pumping and lay out the measured viewport; do not treat the requested size as an exact result. These checks do not establish human drag behavior or another native backend.

Complete consumer and validation¶

The interactive layout workspace installs 640 by 480 through 4096 by 4096 content bounds before embedding its measured grid page:

cargo run -p ravet-examples --bin layout_workspace --locked

Its existing --fixture continues to exercise unbounded programmatic sizing and undersized presentation retention. The separate explicit constraint fixture builds the framework sources and only its own hidden windows:

python3 scripts/check-window-constraints.py

An optional --runner accepts an executable runner command; it is parsed into arguments and never passed to a shell. The fixture requires macOS 12 or later, Rust and Xcode command-line tools. It uses process-local settings, opens no audio/MIDI devices and removes its exact-window notification observers before dropping the borrowed contexts or editors. Informational min/max queries scan at most eight windows in its own process and match a unique bounded fixture title; they do not inspect other applications or accessibility settings.

Five portable numerical groups cover finite bounds, free/aspect fitting, incompatible/extreme requests and deterministic sweeps. The existing tutorial allocation-counter fixture measures 19,998 resolver calls with zero allocations. Two actual owned hidden windows cover 22 measured viewport/grid transitions, four undersized states with unchanged prior presentation, exact native-property readback, incompatible proposal rejection and restoration without another size request. Four actual synchronous resize callbacks reject nested policy and size operations while preserving admitted readback. Both windows retain the standard popup and editor-before-parent cleanup. This is native property, callback and WebKit geometry evidence; no human drag, device, DAW, accessibility-tree or screen-reader certification is inferred.