[rkaraivanov]

Description

Adds showAt(rect: TooltipRect) to igc-tooltip. It shows the tooltip at a point or against a rectangle in viewport coordinates, with no anchor element. The main use is a tooltip that follows the pointer over a canvas, a chart or an SVG drawing.

canvas.addEventListener('pointermove', (e) =>
  tooltip.showAt({ x: e.clientX, y: e.clientY })
);
canvas.addEventListener('pointerleave', () => tooltip.hide());

API

• showAt({ x, y, width?, height? }). TooltipRect is a plain object type (jsonAPIPlainObject), so a DOMRect fits it and Blazor can pass a struct. show() keeps its signature, because Blazor cannot easily express a union overload.
• A call while the tooltip shows at a point moves it, with no animation and no events.
• placement, offset, withArrow and the flip at the viewport edges apply.
• At a point, the tooltip binds no triggers and no aria-describedby, and it ignores the pointer on itself. The app shows and hides it. Escape still closes it.
• After the tooltip closes, the configured anchor applies again, also an anchor that changed while it showed at the point.

Fixes found on the way

• Fallback strategy, for all popover-based components:
  • A popup inside an ancestor with CSS zoom is now at its anchor, with a centered arrow.
  • A popup whose anchor is in a modal dialog no longer lags one frame behind on scroll.
• Arrow: both strategies now center it from the client rectangles. With a -start or -end placement on a small anchor, it stays inside the tooltip.
• Tooltip:
  • A trigger that is in both show-triggers and hide-triggers is handled once.
  • The anchor triggers are no longer bound twice.
  • show(target) after an anchor change in the same task shows at the target.
  • Escape and the pointer work after the tooltip moves in the DOM.
  • A tooltip that is not connected no longer takes Escape.
  • Removing placement no longer throws.

Known limits

• The point is in viewport coordinates and does not follow a page scroll. On a scroll, call showAt() again or hide the tooltip.
• With CSS anchor positioning, a flipped side stays flipped while the tooltip shows (the browser remembers the last position). The next show starts from placement again.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)

Related Issues

Closes #2538

Checklist

• My code follows the project's coding standards
• I have tested my changes locally
• I have updated documentation if needed
• If I changed the public API on purpose, I have run npm run public-api:update and committed public-api.json
• I have added a CHANGELOG.md entry under [Unreleased]

🤖 Generated with Claude Code

[Copilot]

🟡 Changes recommended

The anchor accessor introduces a separate property-change mechanism that conflicts with coding guidelines requiring @coercedProperty and onChange for per-set side effects.

1 open issue

• Use onChange for anchor side effects · New

What changed in this PR

Adds showAt(rect: TooltipRect) so tooltips can follow pointer coordinates or computed rectangles without an anchor element, addressing #2538 for canvas, chart, and SVG use cases.

Changes:

• Adds rectangle anchoring to the shared popover implementation and exposes it through the tooltip API.
• Fixes zoom-aware positioning, arrow placement, trigger binding, and tooltip lifecycle behavior.
• Adds positioning tests, a chart example, specifications, and public API documentation.

File	Description
stories/​tooltip.stories.ts	Adds a chart demo with pointer-following and bar-anchored tooltips.
src/​internals/​utils/​dom.ts	Adds a shared CSS zoom helper.
src/​components/​types.ts	Defines the public TooltipRect type.
src/​components/​tooltip/​tooltip.ts	Adds showAt() and synchronizes anchor changes.
src/​components/​tooltip/​tooltip.spec.ts	Tests rectangle positioning and tooltip regressions.
src/​components/​tooltip/​themes/​tooltip.base.scss	Removes a redundant popover background override.
src/​components/​tooltip/​spec.md	Documents rectangle anchoring and its behavioral contract.
src/​components/​tooltip/​service.ts	Makes the Escape callback collection readonly.
src/​components/​tooltip/​controller.ts	Manages rectangle state, triggers, and listener restoration.
src/​components/​tabs/​tab-dom.ts	Reuses the shared zoom helper.
src/​components/​popover/​themes/​light/​popover.base.scss	Adds proxy-anchor styling and scopes container styles.
src/​components/​popover/​spec.md	Documents rectangle anchors and positioning limits.
src/​components/​popover/​position/​types.ts	Defines rectangle inputs for positioning strategies.
src/​components/​popover/​position/​strategy.ts	Adds a dedicated repositioning operation.
src/​components/​popover/​position/​native.ts	Updates native repositioning and shared arrow handling.
src/​components/​popover/​position/​floating.ts	Accounts for zoom and top-layer anchors in fallback positioning.
src/​components/​popover/​position/​arrow.ts	Centralizes zoom-aware arrow centering and bounds.
src/​components/​popover/​popover.ts	Implements rectangle proxy anchors and their lifecycle.
src/​components/​popover/​popover.spec.ts	Tests rectangle anchors and top-layer positioning.
public-api.json	Records the new type, method, and popover property.
CHANGELOG.md	Describes the feature and related fixes.

_{Review effort: Balanced}

[simeonoff]

Ran the full suite in Chromium, and the tooltip/popover/select/combo/dropdown specs in WebKit and Firefox 157 against master. No new failures, and the new showAt() specs pass in all three. Existing behavior stays the same unless showAt() is called, so this looks good to me.

A few non-blocking things:

• TooltipRect and PopoverRect describe the same thing. PopoverRect also ends up in public-api.json through the anchorRect property of igc-popover, but the type itself isn't exported. I'd either mark anchorRect as @internal or export the type. PopoverRect = Required<TooltipRect> would make the relation explicit.
• _resolveAnchor() in tooltip.ts and resolveAnchor() in the controller share a name but do different things. The tooltip one only applies a pending anchor change, so in show() it reads like a forced re-resolve. Something like _applyPendingAnchor() would be clearer.
• The "only the rect moved" check in update() of popover.ts relies on properties.size === 1. It works today, but if the tooltip changes any other property in the same update, it silently falls back to the slower update() path. Checking the relevant properties by name would be more explicit.
• The new _placement getter does the same as resolvePlacement() from popover/position/types.ts. Reusing it keeps the default placement in one place.