fix: keep re-measuring rendered height instead of a one-shot onload

[NuPlay]

Problem

The rendered height was measured exactly once, inside window.onload, using offsetHeight. Anything that changed the layout after that point was never reported back to SwiftUI, so the view kept a stale height and the content was clipped:

• a <details> toggled open (<DETAILS>...</DETAILS> #18)
• long documents whose final layout settles after load (HTML content clipping #59)
• late images and web fonts, rotation, Dynamic Type changes

Adding continuous re-measurement alone would not have worked, because updateUIView/updateNSView called loadHTMLString unconditionally on every SwiftUI state change, including the dynamic height updates this view produces itself. That reset all in-page state, so an opened <details> collapsed again immediately and the observers would have fought a reload loop. It also re-paid the full parse and layout cost on unrelated redraws (#60).

Changes

RichTextConstants.htmlTemplate - replace the one-shot window.onload measurement with an observed syncHeight():

• ResizeObserver on the container reports every layout change
• MutationObserver re-binds media handlers for nodes added later
• toggle is listened for in the capture phase, since it does not bubble
• document.fonts.ready, load, resize and orientationchange cover the remaining late-layout cases
• height is ceil(max(scrollHeight, getBoundingClientRect().height)), so fractional layout heights no longer clip the last line
• repeated identical heights are dropped before crossing the JS/native bridge

Webview.swift - the coordinator remembers the loaded document and reloads only when the generated HTML actually differs.

Verification

Ran the old and new scripts side by side in a real browser against a <details> repro, with the webkit.messageHandlers bridge stubbed to record what would be posted to the native side:

	after load	after opening <details>	after closing
before	91	91 (actual height 204)	91
after	91	204	91

Tests cover the template contract: the observers are present, window.onload is gone, and the seven String(format:) placeholders still map to the arguments WebView.generateHTML() supplies.

Fixes #18
Fixes #59
Refs #23, #60

[Copilot]

🟡 Changes recommended

The new reload-suppression logic ignores conf.baseURL, so configuration changes affecting relative URL resolution may not take effect when HTML is unchanged.

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Pull request overview

This PR fixes stale/clipped rendered height reporting by switching the HTML template from a one-shot window.onload measurement to continuous height synchronization, while preventing SwiftUI-driven update cycles from repeatedly reloading the document and resetting in-page state.

Changes:

• Updated RichTextConstants.htmlTemplate to continuously re-measure height using observers/events and to avoid redundant bridge calls.
• Updated WebView to skip loadHTMLString when the generated HTML hasn’t changed, avoiding reload loops and preserving in-page state.
• Added tests to pin the HTML template’s measurement strategy and %@ placeholder ordering contract.

File summaries

File	Description
Tests/RichTextTests/RichTextSwiftTestingTests.swift	Adds contract tests for continuous height observation and placeholder ordering.
Sources/RichText/Views/Webview.swift	Avoids redundant reloads by caching the last generated HTML.
Sources/RichText/Models/RichTextConstants.swift	Replaces one-shot height measurement with ongoing observation and de-duplication.

Review details

Suppressed comments (1)

Sources/RichText/Views/Webview.swift:297

• The reload-suppression guard only compares the HTML string; it should also consider conf.baseURL (and then pass that same captured baseURL into loadHTMLString) so configuration changes that affect URL resolution still take effect.

        let htmlString = generateHTML()
        
        guard coordinator.loadedHTML != htmlString else {
            webViewLogger.debug("Skipping reload, generated HTML is unchanged")
            return
        }
        
        coordinator.loadedHTML = htmlString
        
        webViewLogger.debug("Loading HTML content (\(htmlString.count) characters)")
        
        webView.loadHTMLString(htmlString, baseURL: conf.baseURL)

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

🟡 Changes recommended

The new reload-suppression cache in Webview.swift is not cleared on navigation failures, which can cause subsequent updates to skip reload and leave the web view stuck after an error.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (1)

Previously missed (1) — in code that hasn't changed since the last review.

Sources/RichText/Models/RichTextConstants.swift:166

• MutationObserver currently calls attachMediaHandlers() (full img/video rescan) and syncHeight() for every subtree mutation. On large/interactive documents this can fire in bursts and repeatedly scan the whole DOM; debouncing to once per animation frame reduces work without changing behavior.

              new MutationObserver(function () {
                attachMediaHandlers();
                syncHeight();
              }).observe(richTextContainer, { childList: true, subtree: true });
            }

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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