smart_measurer 0.1.4

Measure a widget's real size and react to it, with frame-accurate precision tracking and a zero-delay, size-aware decoration painter for pure-drawing use cases.

Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

0.1.4 - 2026-08-11

Added

• shrinkToFit on SmartMeasurer / SimpleMeasurer — when constrainToAvailableSpace is true and content does not fit the available space on the non-scrollable axis, setting shrinkToFit to true scales the content down to fit (like BoxFit.scaleDown) instead of clipping it. Defaults to false (clipping).

Changed

• constrainToAvailableSpace without scrolling now actually prevents visual overflow. Previously it only applied a ConstrainedBox with the same max constraints, which is a no‑op on Flex children that overflow their own bounds. Now a ClipRect (and optionally FittedBox via shrinkToFit) ensures the content is visually clipped or shrunk to the available space, matching the flag’s contract.

0.1.3 - 2026-08-11

Added

• sizeChangeThreshold on SmartMeasurer / SimpleMeasurer — ignores measurement deltas smaller than a given number of logical pixels, to absorb sub-pixel jitter coming from an animating parent layout instead of rebuilding on every one. When a change is filtered out but the generation/constraints did change, the previous size is kept rather than snapping to the near-identical new one, to avoid visible jitter.

• onSizeChanged on SmartMeasurer / SimpleMeasurer — a side-effect callback fired on every committed precise measurement, independently of builder, for cases (analytics, syncing a scroll offset, driving an external animation) that shouldn't require rebuilding the whole builder subtree.

• notifyDebounce on SmartMeasurer / SimpleMeasurer — debounces rapid successive measurements (screen rotation, keyboard animation) into a single update instead of one per frame.

• animationDuration / animationCurve on SmartMeasurer / SimpleMeasurer — animates the displayed precise size smoothly instead of snapping to it immediately, for a "grow/shrink" transition. Has no effect on estimated sizes.

• SmartMeasurerController — an external ChangeNotifier exposing size, isPrecise, and constraints, so code outside of builder can read the current measurement. Pass it via the new controller parameter on SmartMeasurer / SimpleMeasurer. Notifications are deferred to a post-frame callback, so it's always safe to call setState from a listener.

• estimateStrategy (SmartMeasurerEstimateStrategy: zero, previousSize, constraints, custom) on SmartMeasurer / SimpleMeasurer — an explicit, extensible replacement for useConstraintsAsInitialEstimate, which is now deprecated but still honored when estimateStrategy is left unset.

• ignorePointerDuringEstimate on SmartMeasurer / SimpleMeasurer — wraps the result in IgnorePointer while isPrecise is false, so taps never land on a provisional layout.

• onDebugWarning on SmartMeasurer / SimpleMeasurer — redirects the package's internal warnings (invalid estimate, missing measuredChild, etc.) to a custom sink instead of debugPrint, so production apps can route them into their own logging pipeline.

• placeholderBuilder on SmartMeasurer / SimpleMeasurer — a widget shown instead of builder's output until the very first precise measurement is ever obtained (e.g. a skeleton). The real child keeps measuring offstage in the background so the switch-over happens as soon as layout is ready.

• debugPaintEstimatedSize on SmartMeasurer / SimpleMeasurer — debug-only red/green border around the result depending on isPrecise, to spot flicker or measurement issues visually. Compiled out entirely outside of debug builds.

• unconstrained on SmartMeasurer — auto-wraps measuredChild in an UnconstrainedBox, the same trick SimpleMeasurer already used internally, so it always reports its natural size.

• constrainToAvailableSpace, scrollable, scrollDirection on SmartMeasurer / SimpleMeasurer — optional built-in handling for content that might exceed the available space, instead of requiring users to combine LayoutBuilder + ConstrainedBox / SingleChildScrollView by hand around every measurer.

• SmartMeasurerGroup — a new, lighter widget that measures a list of children at once and hands back their sizes (List<Size>) plus an allPrecise flag, for layout decisions that depend on several sizes at once (e.g. equalizing a row of chips) without nesting multiple SmartMeasurers.

• MeasuredDecoration.onSizeChanged — an optional callback fired after layout whenever the child's size changes, independent of painter and without forcing an extra paint. Deferred to the end of the frame, so it's always safe to call setState from it.

Changed

• Breaking: MeasuredDecoration.painter signature. painter now receives the child's BoxConstraints in addition to Canvas and Size: void Function(Canvas canvas, Size size, BoxConstraints constraints). Existing painters need one extra parameter added to their signature; no other change is required. See the README's "Migrating from 0.1.x" section.

Deprecated

• useConstraintsAsInitialEstimate on SmartMeasurer / SimpleMeasurer — superseded by estimateStrategy (SmartMeasurerEstimateStrategy.constraints). Still fully functional as a fallback when estimateStrategy is left unset; no removal planned in the near term.

Notes

• Aside from the MeasuredDecoration.painter signature change, every addition in this release is optional and additive — existing code using SmartMeasurer, SimpleMeasurer, or SmartMeasurerController-less setups keeps working unchanged.

0.1.2 - 2026-08-11

Added

• debugLabel on SmartMeasurer (optional, propagated by SimpleMeasurer).
  Provides a human-readable name for the widget, visible in debug error messages (duplicate key exceptions) and in the widget inspector, helping to distinguish multiple nested SmartMeasurer instances.

• debugFillProperties on RenderMeasuredDecoration so the inspector now shows painter identity and paintBehindChild value, matching what _RenderMeasuredChild already exposes for the measurement infrastructure.

Changed

• Simplified _isValidForConstraints – the manual ternary check was redundant because BoxConstraints.maxWidth / maxHeight already return double.infinity when the axis is unbounded. Replaced by a direct call to constraints.isSatisfiedBy(size), which is the canonical method and also slightly more efficient.

• Renamed shadowed parameter in _scheduleNotification from constraints to usedConstraints, avoiding a name conflict with the inherited RenderBox.constraints getter. No behaviour change.

• Frame‑detection in the debug “no precise measurement” warning re‑implemented with a postFrameCallback‑based flag instead of SchedulerBinding.currentFrameTimeStamp. This avoids a potential assertion error if _checkMissingChild is called outside an active frame, and matches the pattern already used elsewhere in the file. Debug‑only, no release impact.

Notes

• All changes are internal to the implementation; the public API is fully backward‑compatible with 0.1.1. The debugLabel parameter is an optional addition and does not affect existing code.

0.1.1 - 2026-08-11

Fixed

• SimpleMeasurer reported a fake, self-referential size instead of the child's real size. The child was overlaid with Positioned.fill, which forces tight constraints on it (min == max, derived from the decoration builder had just returned). Since a RenderBox under tight constraints must report exactly those constraints back, the "measured" size was really just an echo of the previous size plus whatever offset the decoration added — never the child's actual natural size. This broke the primary use case shown in the README (a decoration that sizes itself to a piece of text). measuredChild is now wrapped in UnconstrainedBox instead, guaranteeing it is always laid out with no constraints and always reports its true natural size, regardless of what builder returns or what constraints are imposed on SimpleMeasurer by its own parent.

• MeasuredDecoration could keep painting a stale decoration. painter and paintBehindChild were plain field assignments in updateRenderObject, so replacing painter with a new closure (e.g. one capturing a different color) did not trigger a repaint — the previous frame's drawing stayed on screen until something else happened to repaint the render object. painter and paintBehindChild are now real setters that compare the old and new value and call markNeedsPaint() when they actually change.

Changed

• SimpleMeasurer gained an alignment parameter (AlignmentGeometry, default Alignment.center), controlling where the child is positioned within the decoration now that it's no longer force-fit with Positioned.fill. This restores (and makes explicit) the centered overlay behavior implied by the original README example.

• The "no precise measurement after 3 frames" debug warning in SmartMeasurer now counts real frames, not builds. Previously the internal counter incremented on every call to build(), so a parent that rebuilds more than once per frame could trigger the warning long before three actual frames had passed. It's now debounced with a SchedulerBinding.addPostFrameCallback-based flag, so it only advances once per frame regardless of how many times build() runs within it. Debug-mode only; no effect on release builds.

Notes

• No public API was removed or had its meaning changed — SimpleMeasurer gained one new optional named parameter (alignment), everything else is source- and behavior-compatible for correctly-functioning code. Any code that was implicitly relying on SimpleMeasurer's old (incorrect) tautological sizing behavior will now see accurate sizes instead — if your decoration looked fine before, it will look at least as good now; if it looked subtly "stuck" or unresponsive to content changes, this is why, and it's now fixed.

0.1.0 Initial release

• Initial release of smart_measurer: SmartMeasurer, SimpleMeasurer, and MeasuredDecoration.