WebView: release-build inspector + cross-platform background-colour Options API#24
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jakepenn merged 3 commits intoMay 21, 2026
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Re-applies 7330a68, which was lost in the 58c87ee develop merge. macOS: - Drop the JUCE_DEBUG guard around `developerExtrasEnabled` so the Safari Web Inspector is reachable from release builds. - Set `inspectable: YES` on the WKWebView for macOS 13.3+ / iOS 16.4+, where Apple made it a required public-API opt-in alongside the legacy preference key. Windows: - Drop the `#if !JUCE_DEBUG put_AreDevToolsEnabled(false)` block so WebView2's DevTools stay enabled by default in release. Plugins ship as release builds by definition — the developer-only gating made the inspector unreachable in the one environment where plugin UIs actually run, which made webview-based UI work painful to debug. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Mirrors the existing WinWebView2::withBackgroundColour API surface so a cross-platform host can configure both backends from one place. When set, the WKWebView's NSView gets `drawsBackground = NO` via KVC — the same private-but-stable trick Tauri/wry uses (`wry/src/wkwebview/ mod.rs`, stable since macOS 10.14, the path Safari and Xcode follow). On macOS 12+ / iOS 15+ the public `setUnderPageBackgroundColor` is also set so the overscroll bounce area picks up the chosen colour. Opt-in: only takes effect when withBackgroundColour() is called on the AppleWkWebView options. Default behaviour is unchanged. Why: WKWebView paints an opaque default background (white in light mode, a system grey in dark mode) until the page renders, which produces a one-frame flash whenever the OS surface is shown or resized into real bounds. Plugins doing any form of webview-host visibility gating (hidden-on-load, 1×1 during boot, etc.) hit this every launch. Linux backend (juce_WebBrowserComponent_linux.cpp) does not yet expose an equivalent — webkit_web_view_set_background_color isn't bound through the JUCE symbol resolver. Adding that is a follow-up. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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WKWebView copies WKWebViewConfiguration values at init, so KVC-setting `drawsBackground` on the config after webview creation was a no-op — the surface kept its opaque default and the very first frame still flashed white/system-grey on reveal. Move the call to the WebView itself, where it actually takes effect. Also belt-and-braces the underlying NSView's CALayer on macOS: some recent WebKit builds composite the host NSView independently of the WKWebView's drawsBackground state, so a transparent layer background catches the remaining frame. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Inspector access in release builds (
c93b9139ed)JUCE_DEBUGguard arounddeveloperExtrasEnabled, addsetInspectable: YESfor macOS 13.3+ / iOS 16.4+.#if !JUCE_DEBUG put_AreDevToolsEnabled(false)block.Cross-platform pre-paint background-colour control (
bdddb1619c)WebBrowserComponent::Options::AppleWkWebView::withBackgroundColour(Colour)mirroring the existingWinWebView2::withBackgroundColour. When set, macOS usesdrawsBackground = NOvia KVC (same private-but-stable trick Tauri/wry uses) and, on macOS 12+, the publicsetUnderPageBackgroundColor. Opt-in — default behaviour unchanged.WinWebView2::withBackgroundColour. No code change needed there.webkit_web_view_set_background_colorthrough JUCE's symbol resolver — flagged as a follow-up in the commit message.Why
Plugins ship as release builds and run inside a DAW host —
JUCE_DEBUG-only gating made the inspector unreachable in the only environment plugin UIs actually run in.WKWebView paints an opaque default background (white in light mode, a system grey in dark mode) until the first content frame renders. Plugins that gate webview visibility on a first-paint handshake (1×1 during boot, hidden-then-shown, etc.) see this flash every launch. The
drawsBackgroundKVC trick lets the host paint its own background through the transparent surface — the same approach Tauri/wry takes across all three platforms.Test plan
juce::WebBrowserComponent. Attach Safari → Develop → [Mac] → [WebView entry]; inspector connects.Options::AppleWkWebView{}.withBackgroundColour(Colour(0,0,0,0))set on a webview that gates visibility on a first-paint handshake, confirm no flash on first reveal.withBackgroundColour: confirm behaviour is unchanged from upstream.withBackgroundColourdoesn't break a release build.WinWebView2::withBackgroundColourcontinues to work; Release inspector still right-click → Inspect.