tauri-plugin-webview-capture

A Tauri 2 plugin that captures a webview's rendered output (DOM + WebGL composite) as PNG. It captures the webview's own render, not the screen — so on macOS a window fully occluded by other apps is still captured without bringing it to the front.

Tauri's core has no webview capture API. This plugin captures through each OS's native API:

OS	API	Status
macOS	ScreenCaptureKit SCScreenshotManager (own-process windows)	runtime-verified, including occluded capture
Windows	ICoreWebView2.CapturePreview	compiles in the consuming app's three-OS CI gate; runtime capture unverified
Linux	WebKitGTK WebView::snapshot (GTK3)	compiles in the consuming app's three-OS CI gate; runtime capture unverified

On macOS it captures the OS compositor's window composite rather than a single webview's takeSnapshot — the main webview and every child webview (embedded browser views included) land in one image with no holes. getCurrentProcessShareableContent scopes the capture to the app's own windows, so no Screen Recording permission is needed. (The older CGWindowListCreateImage is obsolete on macOS 15 and blocks during rendering, so it was replaced with ScreenCaptureKit.)

Commands

• snapshot({ path }) — save a single PNG. Parent directories are created. Returns the saved path.
• snapshot_region({ x?, y?, w?, h? }) — crop the window composite to a logical rect (CSS px, window coordinates) and return it as base64 PNG with no disk round trip. Omitting the rect captures the whole window. The crop uses CGImageCreateWithImageInRect, so only the region is encoded. macOS only (Windows/Linux return an error).
• record({ dir, frames, intervalMs }) — save a burst of PNGs (dir/f0000.png …). A built-in video source.
• set_occlusion({ enabled }) — toggle occlusion detection (macOS). false keeps the webview rendering in the background at a battery cost. Windows and Linux have no equivalent throttle, so it is a no-op there. snapshot and record disable it automatically for the capture instant.
• analyze_regions({ dir, regions }) — mean luma of each region (fractional coordinates 0..1) per captured frame. Returns frames×regions.
• analyze_frame_diffs({ dir, regions, thresh? }) — the fraction of pixels changed from the previous frame (change detection — it also catches same-brightness content transitions). Returns frames×regions.

How occluded capture works

macOS WebKit throttles WebGL rendering in fully covered windows. snapshot and record disable occlusion detection just before capturing (_setWindowOcclusionDetectionEnabled:false, a private WKWebView API), give rendering 200 ms to resume, capture, and restore the setting — the idle battery cost stays zero.

Windows (WebView2) and Linux (WebKitGTK) have no macOS-style occlusion throttle — they pause only when minimized or hidden and keep rendering while covered — so set_occlusion being a no-op there is the correct behavior.

Usage

// app entry point
tauri::Builder::default()
    .plugin(tauri_plugin_webview_capture::init())
    // ...

// capabilities/*.json
"permissions": ["webview-capture:default"]

import { invoke } from "@tauri-apps/api/core";
await invoke("plugin:webview-capture|snapshot", { path: "/tmp/shot.png" });

Status

The macOS implementation is runtime-verified, including occluded capture. The Windows and Linux paths compile in the consuming app's three-OS cargo check CI gate — that first real check surfaced and fixed genuine API drift (the WebView2 completion-handler signature, the WebKitGTK 2.0 method names, cairo's png feature) — and their runtime capture behavior still needs on-OS verification.

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한국어 안내는 README.ko.md에 있습니다.

License

MIT