Changelog

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All notable changes to Fresco are documented here. The format is based on Keep a Changelog and the project adheres to Semantic Versioning.

0.3.1 — 2026-05-17

Fix :pan_optimized not actually engaging in OSD 4.1.x. The 0.3.0 fast-pan installer probed for viewer.drawer.draw, but OSD's modern canvas drawer (4.1 onwards) exposes .update() instead — no .draw() method exists on the drawer object. The check silently returned, so the fast path never engaged for anyone on the default OSD version Fresco pins to. Consumers saw no perf change between pan_optimized={true} and the default; the new event was never emitted.

This patch is a true no-op for behavior unless you're on :pan_optimized — in which case it switches you from "silently inert" to "actually engaged."

Fixed

  • installFastPan now probes for both drawer.update and drawer.draw and suppresses whichever exists. OSD 4.1.x uses update; older or custom drawers may still use draw. Being defensive about both shapes means future drawer revisions don't silently break the fast path again.
  • commitFastPan now triggers the post-pan repaint via viewer.forceRedraw() (a stable OSD public API) instead of calling the (potentially-renamed) drawer method directly.
  • Added console.warn on every silent-bail path inside installFastPan / startFastPan. Previously, if the install early-returned (no drawer, rotate active, unknown drawer methods, missing canvas), the consumer had no signal — the fast-pan event just never fired. Now developers see exactly why the fast path didn't engage.

Notes

  • No public API changes. :pan_optimized attr and fast-pan event surface are identical to 0.3.0. Etcher 0.2.8's subscription continues to work unchanged.
  • After upgrading, pan_optimized={true} viewers will now actually fire fast-pan events. Overlay extensions (Etcher ≥ 0.2.8) will start receiving them and applying the matching CSS transform.

0.3.0 — 2026-05-17

CSS-transform pan fast path tuned for long-scroll reading content (manhwa / manga / comics / document viewers) where the user is panning continuously, not zooming. Opt-in via a new :pan_optimized attr on Fresco.viewer/1. Default off — existing viewers see no behavior change. Bumped to minor because the release introduces a new public attr and a new synthetic event (fast-pan) that overlay extensions need to coordinate with.

Added

  • New :pan_optimized attribute on Fresco.viewer (defaults false). When true, the JS hook installs a pan interceptor that temporarily swaps OSD's drawer for a no-op during the gesture, applies a GPU-composited transform: translate3d to OSD's canvas element per frame, and emits a fast-pan event in three phases (start, delta, end). Drops per-frame cost from ~10–20ms to <1ms on iOS Safari for pure-pan motion. Bails to OSD's normal redraw path on zoom-change, overscan (cumulative delta > 50% of viewport height), and when :rotate is also active (rotation invalidates the simple translate math).
  • New fast-pan event in the handle.on(eventName, fn) channel. Only emitted when :pan_optimized is set on the viewer. Payload: { phase: "start" | "delta" | "end", x, y } with cumulative screen-pixel offset. Overlay extensions apply the same translate3d(x, y, 0) to their container so they stay aligned with the canvas during the fast-path window. Etcher >= 0.2.8 listens automatically.
  • New handle._emit(eventName, payload) internal method on the viewer handle for Fresco's own modules to fire synthetic events through the existing subscriber list. Underscore-prefixed because consumers should never call it — emit is owned by Fresco's internals; consumers listen via handle.on(...).

Notes

  • No breaking changes. The fast-pan event is emitted only when the consumer opts into :pan_optimized; older Etcher (or any other overlay) paired with non-opted viewers sees nothing different.
  • Older Etcher (< 0.2.8) paired with a :pan_optimized viewer will see annotations visibly drift during the pan window. Either upgrade Etcher or hold off on opting in to :pan_optimized until Etcher is on >= 0.2.8.
  • Tessera (the DZI deep-zoom layer) is unaffected — it's a source provider, no overlay.

0.2.0 — 2026-05-15

Official, documented escape hatch to the underlying OpenSeadragon Viewer instance. No breaking changes — handle.viewer (the original undocumented name) remains supported as a back-compat alias. Bumped to a minor version because the new field carries a public stability obligation (Fresco can no longer freely rename or reshape the OSD viewer reference), not because the code change itself is large — it's a one-line aliasing.

Added

  • handle.openSeadragon — official, documented access to the underlying OpenSeadragon Viewer for advanced consumers and layered packages. Use it for OSD APIs Fresco doesn't expose first-class: custom pan/zoom constraints (panHorizontal, minZoomImageRatio, …), raw OSD event handlers (canvas-double-click, canvas-key, …), OSD plugin registration, gesture rebinding. See the new "Advanced: OSD escape hatch" section in README.md for the stability contract — in particular, the rule that consumers reaching for it routinely should file an issue so common patterns can graduate to first-class Fresco APIs.

Notes

  • handle.viewer (the existing back-compat alias for openSeadragon) remains supported indefinitely. Etcher already depends on this field across five call sites for image-space coordinate math — that's the in-tree consumer whose usage pattern motivated formalizing the contract. New code should prefer handle.openSeadragon; Etcher can migrate at its own pace.
  • No breaking changes; no behavior changes for existing consumers.

0.1.6 — 2026-05-15

Documentation + test polish patch. No changes to the rendered output of Fresco.viewer/1 — every existing call site behaves exactly as in 0.1.5. The goal is to make Fresco's genericity (works for any Phoenix app, not just daisyUI consumers) more visible to a new reader, and to backfill render-assertion tests for the attributes added in 0.1.4 / 0.1.5.

Changed

  • README: clarified that the daisyUI mapping for theme={:inherit} is one example among many — any CSS custom properties or fixed colors work. Added a second bare-color example so readers don't infer that daisyUI is required.
  • README: surfaced the theme={:system} dark-mode default that landed in 0.1.4 with a "Heads up" callout in the Theming section, so consumers upgrading from 0.1.3 aren't caught off guard by viewers rendering dark on dark-OS machines.
  • README: documented the FrescoViewer hook name explicitly so consumers maintaining an explicit hooks map (rather than spreading window.FrescoHooks) know what key to register.
  • README: promoted the first-source-only caveat for handle.imageToScreen / screenToImage to a visible ⚠️ Caveat callout in the multi-image section, with one extra sentence on what extension authors should do until multi-image disambiguation ships.
  • README + viewer attr doc: rotation section now says "fifth button" (the row of four built-in buttons + a fifth opt-in rotation button) instead of "fifth icon".
  • priv/static/fresco.js: documented the rationale for pinning OpenSeadragon to 4.1.0 so future maintainers know the bump contract.

Tests

  • Added render-assertion coverage for :theme (all four values), :sources (multi-image JSON payload), :infinite_canvas (modifier class + data attribute), :rotate (data attribute), and the ArgumentError guard that fires when neither :src nor :sources is provided.

0.1.5 — 2026-05-15

One additive feature — a fourth :theme value, :inherit, that lets the parent app drive Fresco's palette via the existing --fresco-* CSS custom properties. Use it to wire the viewer to a parent theme system (daisyUI, Tailwind, custom palettes) so background, dot grid, and nav buttons follow the parent theme as it changes. Fully backwards compatible — existing :system/:light/:dark viewers behave exactly as in 0.1.4.

Added

  • New :inherit value on Fresco.viewer's :theme attribute. When set, Fresco emits data-fresco-theme="inherit" on the host div and skips its own var declarations for that viewer — the six --fresco-* properties stay unset until the parent app's CSS defines them. Pair with a CSS rule on .fresco-viewer[data-fresco-theme="inherit"] mapping the variables to the parent's theme tokens. The structural styles (background-color + dot grid pattern) still apply; only the color values come from the parent.

Changed

  • The base .fresco-viewer { --fresco-bg: …; … } rule is now scoped to .fresco-viewer:not([data-fresco-theme="inherit"]) so it doesn't fight the parent's vars. The @media (prefers-color-scheme: dark) branch picks up the same :not() exclusion. Visible only to consumers who pass theme={:inherit}; everything else stays the same.

0.1.4 — 2026-05-14

Three additive features — opt-in 90° rotation, multi-image canvas layout, and light/dark/system theming. The API surface stays backwards-compatible (all existing attrs unchanged, all new attrs have defaults), but the new :theme defaults to :system, which means viewers on dark-OS machines will now follow prefers-color-scheme and render dark by default. Pass theme={:light} to lock to the old always-light look.

Added

  • New :rotate attribute on Fresco.viewer (defaults to false). When true, appends a 90°-clockwise rotation button between the Fullscreen and Zoom-in icons. Rotation is tracked independently of zoom/pan — "Reset view" deliberately doesn't undo it.
  • New :sources attribute for laying multiple images out on one canvas. Each entry is a %{src, x, y, width} map in viewport units; the first image conventionally anchors the layout at width: 1, so x: 1.1 puts the next image just to the right. Heights derive from each image's natural aspect ratio. Each entry's src runs through the same source-provider chain as :src, so plain images and DZI tile pyramids (via Tessera) can be mixed on a single viewer. Live re-renders that change the list re-open the viewer while preserving the current zoom/pan.
  • :src is now optional. At least one of :src or :sources must be given; the component raises otherwise. Existing single-image callers keep working unchanged.
  • New :theme attribute — :system (default), :light, or :dark. Plumbed to data-fresco-theme on the host div. :system follows the OS via prefers-color-scheme; the other two force a fixed palette regardless of OS preference.
  • Six CSS custom properties on .fresco-viewer expose the entire palette surface: --fresco-bg, --fresco-grid-dot, --fresco-nav-bg, --fresco-nav-bg-hover, --fresco-nav-fg, --fresco-nav-focus. Override them in user CSS to wire fresco to a parent theme system (daisyUI, Tailwind, custom palettes) — README has a daisyUI mapping example.

Changed

  • Default viewer rendering follows prefers-color-scheme (:theme defaults to :system). Viewers on dark-OS machines that previously rendered light will now render dark unless explicitly pinned via theme={:light} or an inherited explicit theme.
  • handle.imageToScreen / handle.screenToImage continue to operate on the first source when multiple are present. Multi-image coordinate disambiguation is planned but not yet implemented.

0.1.3 — 2026-05-14

Opt-in infinite-canvas mode + a default dot-grid background. No breaking changes — every existing viewer keeps the stock clamped behavior unless infinite_canvas is explicitly set, and the grid is invisible by default (OSD's canvas paints over it).

Added

  • New :infinite_canvas attribute on Fresco.viewer (defaults to false). When true:
    • visibilityRatio drops to 0 and constrainDuringPan flips to false, so the user can pan freely beyond the image edges.
    • minZoomImageRatio lowers to 0.05 so the image can shrink to a thumbnail in the middle of a vast canvas.
    • The void around the image lights up with the dot-grid background (see below); the host also picks up a .fresco-viewer--infinite modifier class for any infinite-only styling consumers want to add.
  • Subtle 24×24px dot-grid background on every Fresco viewer (via the new .fresco-viewer base class on the host div). Hidden by default because OSD's canvas paints over it; visible in the void when infinite_canvas is on, or behind transparent / padded images. Override .fresco-viewer in your own CSS for dark mode or a different accent.
  • Documented future API: a planned :sources attribute will accept a list of [%{src: "...", offset: {x, y}}] for multiple images on the same canvas. The current :src stays as the single-image shortcut — no migration when :sources ships.

0.1.2 — 2026-05-14

Small UX + extension-API patch release. No breaking changes for existing consumers; the click-to-zoom default flip is documented below because it's user-visible.

Added

  • handle.appendNavButton(...)'s returned remover now carries .setIcon(svgString), .setTitle(text), and .el (the underlying <button> element). Extensions can mutate a button after creation without re-adding it (which would reshuffle its position in the nav column). Used by Etcher 0.2's visibility toggle to flip eye ↔ eye-slash.

Changed

  • Mouse single-click no longer zooms. gestureSettingsMouse.clickToZoom defaults to false; dblClickToZoom, scroll-to-zoom, and pinch-to-zoom on touch are unchanged. Single clicks now reliably pass through to overlays that want them (e.g. annotation selection) instead of fighting OSD's built-in click-to-zoom.

0.1.1 — 2026-05-12

Small additive release for layered libraries. No breaking changes.

Added

  • handle.appendNavButton(svg, title, onClick) — extensions append a button to the same .fresco-nav flexbox column that holds the built-in zoom-in / zoom-out / reset / fullscreen. Returns an unsubscribe function that removes the button on cleanup. Used by Etcher to add a pencil button that toggles annotation mode.
  • animation and update-viewport events bridged on the viewer handle (handle.on("animation", fn)). The existing zoom / pan events only fire on the intent of an input; the new ones fire on every spring-interpolated frame so overlays glide with the image instead of jumping at endpoints.

Changed

  • <Fresco.viewer> now sets phx-update="ignore" on its host div. Without it, LiveView morphdom patches walk the viewer's children on every render and wipe OSD's runtime-added canvas + extension overlays. The hook still receives updated callbacks for attribute changes (e.g. data-src swaps continue to work) — phx-update protects children only.
  • Nav column reordered top-to-bottom: fullscreen → zoom-in → zoom-out → reset. Extensions appending via handle.appendNavButton land at the bottom of the column.

0.1.0 — 2026-05-12

Initial release. Polished pan-zoom image viewer for Phoenix apps, with a deliberate extension surface for layered libraries.

Built-in viewer

  • <Fresco.viewer id src class> LiveView function component
  • Pan: click-drag, touch-drag, keyboard arrows
  • Zoom: mouse wheel, pinch, double-click, dedicated buttons, + / - keys
  • Fit-to-view initial state regardless of image / container aspect ratio
  • Heroicons nav overlay at top-left: zoom-in, zoom-out, reset, fullscreen
  • Viewport clamped so the image can't be panned off-screen (visibilityRatio: 1.0, constrainDuringPan: true)
  • Smooth animations tuned for snappy responsiveness (animationTime: 0.3, springStiffness: 10)
  • Browser fullscreen mode

Extension surface

  • window.Fresco.viewerFor(domId) — synchronous lookup of a live viewer handle
  • window.Fresco.onViewerReady(domId, callback) — async-safe lookup that fires the callback as soon as the viewer is ready (handles mount-order races when an extension hook mounts before its host viewer)
  • window.Fresco.registerSourceProvider(predicate, factory) — registers a predicate-matched URL transformer; first registered provider that matches wins, falling back to a default plain-image provider
  • Viewer handle exposes: imageToScreen / screenToImage, getViewportBounds, fitBounds, setSource, swapSourcePreservingBounds, and on(event, handler) for zoom / pan / open / resize events

JS engine

  • OpenSeadragon ~> 4.1 lazy-loaded from jsDelivr on first mount
  • One bundled JS file (priv/static/fresco.js); no npm dep, no build step in consumer apps
  • Heroicons SVGs inlined; no PNG sprite dance against a CDN

Requirements

  • phoenix_live_view ~> 1.1, phoenix_html ~> 4.0, jason ~> 1.4