viewfinder 0.3.2

Modern Flutter photo viewer / gallery. Pinch / double-tap / mouse-wheel zoom with rubber-band edges and fling, drag-to-dismiss, thumbnails, page indicator, and keyboard shortcuts.

0.3.2

Bug fixes

• Added mounted guard to the thumbnail bar's post-frame scroll callback. Previously, if the widget was disposed between scheduling and execution of the callback, the scroll could attempt to run on a defunct state.

0.3.1

API additions

• ViewfinderThumbnails.errorBuilder lets callers customize the placeholder rendered in the thumbnail strip when an ImageProvider fails to decode. When omitted, the library default (ColoredBox(color: Colors.white12)) is used; when provided, the caller's builder runs in its place. Applied to the default tile only — when [itemBuilder] is provided the builder owns the entire visual treatment, including error handling.

Internal

• Removed an internal _precached index set that was deduping precacheImage calls. Successful providers are already deduped by Flutter's ImageCache; failed providers do get re-attempted on subsequent adjacent moves, but the cost is bounded by precacheAdjacent. The set never shrank, so it grew monotonically with every visited index. Its onError callback was also silently swallowing precache failures; precache errors now route through the normal FlutterError.reportError path. The actual display path still surfaces decode errors to the user-supplied errorBuilder.
• Dropped a redundant LayoutBuilder from the image-and-thumb composite. The parent ZoomableViewport already wraps its child in a tight-sized SizedBox, so Image.fit lays out against the viewport without an extra layout pass.

0.3.0

Breaking changes

• ViewfinderImageController.canSwipeHorizontally / canSwipeVertically getters removed in favor of a single canSwipe(Axis axis, {SwipeEdgeMode mode = SwipeEdgeMode.screen}) method. The default behavior is unchanged — canSwipe(Axis.horizontal) returns the same value as the old canSwipeHorizontally did — but the call site changes. Migration: c.canSwipeHorizontally → c.canSwipe(Axis.horizontal), c.canSwipeVertically → c.canSwipe(Axis.vertical).

API additions

• SwipeEdgeMode selects the frame of reference used by canSwipe under rotation. SwipeEdgeMode.screen (the default, used by the bundled gallery) checks the rotated content's AABB against the viewport — symmetric with the internal boundary clamp and matching a screen-axis pager's intent. SwipeEdgeMode.content inverse-projects the viewport into photo space and checks whether it has reached the photo's logical extents [0, viewport.width] / [0, viewport.height]; the result tracks "the user has reached the photo's logical edge in the photo's own frame" at every rotation (no special-casing of cardinal angles). Use it for consumers whose handoff target follows the photo's frame, e.g. a custom pager that swipes along the photo's axes through rotation.

0.2.1

API additions

• thumbCrossFadeCurve is now configurable on ViewfinderImage and ViewfinderItem (default Curves.easeOut). Previously the curve was hardcoded while thumbCrossFadeDuration was the only knob, so callers wanting non-default easing on the thumb-to-main fade had no way in.
• Viewfinder.images(...) and Viewfinder.single(...) now forward the per-page image-display knobs — thumbCrossFadeDuration, thumbCrossFadeCurve, gaplessPlayback — to every ViewfinderItem they construct. Previously these were reachable only by writing a custom itemBuilder; per-page transform overrides (initialScale / minScale / maxScale) still are.

0.2.0

Breaking changes

• Removed ViewfinderInitialScale.value(scale). It was behaviorally identical to ViewfinderInitialScale.contain(scale) — three names for two behaviors. Use contain(scale) instead.
• ViewfinderImage.child and ViewfinderItem.child now require a contentKey. The gallery uses it to detect content swaps and reset the in-page transform on a re-order or swap-in (the image-backed variant gets this for free from the ImageProvider's ==; for .child the rendered widget identity is unreliable, so the caller hands in a stable handle). For a single static .child, any constant works (e.g. contentKey: 'main').

Bug fixes

• ViewfinderImageController.canSwipeHorizontally / canSwipeVertically were computed from raw matrix translation components and so misreported the edge state when rotateEnabled: true. They now project the photo's logical left/right (and top/bottom) edges through the current transform and check whether either has been pulled into the viewport — matching the user's intent ("the photo's left side is exposed → swipe to the previous page") rather than the AABB extents (which, under rotation, are the photo's outermost corners, not its visible sides).
• Viewfinder no longer caches built ViewfinderItems by index. The cache pinned the gallery to the first builder's output, so a dynamic gallery (re-order, swap-in) with the same itemCount would keep showing stale items. Pages are now rebuilt lazily through the underlying PageView.builder / ListView.builder, matching standard Flutter scrollables.
• ViewfinderImage now resets its in-page pan/zoom transform when the underlying content identity changes — the ImageProvider's == for the image-backed variant, the new required contentKey for .child. Previously, slot reuse during a re-order or swap-in left the previous photo's transform applied to the new content. Pure rebuilds with the same content value still preserve the user's transform.

API additions

• Viewfinder.images(...) now forwards reverse, allowEdgeHandoff, and rubberBandPan (previously only available on the main Viewfinder.new constructor).

Validation

• Combining pagerAxis: Axis.vertical with a non-null dismiss is now rejected by a debug assert at construction. Both consume vertical drags; pick one.
• Attaching the same ViewfinderImageController to more than one ViewfinderImage at once is now rejected by a debug assert. Each controller can drive only one viewer; sharing it would silently overwrite the previous binding and produce incorrect reads through scaleState / canSwipe*. Release builds still overwrite silently — assert is debug-only — so callers should not rely on it as a hard guard. Internally, ViewfinderImage now detaches in deactivate and re-attaches in activate so tree rearrangements and GlobalKey moves don't trip the assert.

Documentation

• Viewfinder.rotateEnabled doc said "Boundary clamping is disabled while rotated"; in fact the clamp always runs against the rotated content's AABB. Doc fixed to match the implementation.
• ViewfinderPageIndicatorAdaptive doc clarifies that customizing inner dots.alignment / padding / label.alignment / padding is rejected by a debug assert and silently ignored in release.

0.1.0

• Initial release.
• Viewfinder gallery (PageView-backed, horizontal or vertical pagerAxis) and ViewfinderImage / .child single viewer.
• ViewfinderInitialScale.contain([factor]) / .cover([factor]) accept an optional multiplier — contain(0.8) shows the photo at 80% of fit, cover(1.2) zooms to 120% of fill. .value(scale) remains as an absolute-multiplier shortcut.
• Pinch, pan, double-tap ladder, double-tap-drag continuous zoom, opt-in two-finger rotation; post-release fling on both pan and scale via FrictionSimulation (X / Y / scale axes), anchored to the focal point captured at release.
• Rubber-band elastic edges — pulling a zoomed image past its boundary shows live elastic over-pan with diminishing returns, then animates back on release.
• Custom ZoomableViewport gesture layer that yields edge pans to the parent scrollable via canPan(Axis, int). Yields single-pointer drags along the pager axis when not zoomed, so mouse-drag and trackpad-drag swipe pages on web/desktop.
• Viewfinder.swipeDragDevices — explicit pointer-kind set for the underlying PageView. Defaults to all kinds (kViewfinderDefaultSwipeDragDevices) — overrides Flutter's default ScrollBehavior which excludes mouse on web/desktop.
• ViewfinderItem.thumbImage — low-res preview that cross-fades into the main image on first frame.
• ViewfinderThumbnails (4 positions, .custom()), sealed ViewfinderPageIndicator with Dots / Label / Adaptive variants (Adaptive falls back from dots to a "1 / N" label past maxDots; Label accepts a custom labelBuilder).
• ViewfinderDismiss drag-to-dismiss with slideType: wholePage | onlyImage and an onProgress callback that reports normalized drag progress through the spring-back.
• ViewfinderChromeController — tap-to-toggle, auto-hide after idle, auto-hide while zoomed.
• Keyboard (arrows, PageUp/Down, two-stage Escape), Android back-button two-stage, PopScope-based Hero coherence on pop.
• Mouse wheel + trackpad pinch zoom.
• precacheAdjacent warms imageCache for pages ±N around the current one, using the user's ImageProvider directly so cache keys match what Image() will resolve.
• kViewfinderDefaultFlingDrag = 0.0000135, overridable via interactionEndFrictionCoefficient.
• Semantics labels per image and at gallery level.
• Viewfinder.reverse — forwarded to PageView.reverse for right-to-left galleries.
• Viewfinder.allowEdgeHandoff (default true) — when false, a zoomed image consumes all pan and never yields to the parent PageView; the user must reset zoom before swiping.
• Viewfinder.rubberBandPan / ViewfinderImage.rubberBandPan (default true) — opt out of elastic over-pan for hard edge clamping.
• ViewfinderImage.onScaleStart / onScaleEnd — gesture lifecycle callbacks, useful for haptics and analytics.
• ViewfinderImage.gaplessPlayback / ViewfinderImageItem.gaplessPlayback (default true) — forwarded to the underlying Image.gaplessPlayback.
• ViewfinderImageController.currentTransform getter and jumpToTransform / animateToTransform setters for imperative position / rotation control.