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fix: avoid retained webview flash at default iframe size #326482

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fix: avoid retained webview flash at default iframe size #326482

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3c73f91
fix: avoid retained webview flash at default iframe size
cipheraxat Jul 18, 2026
2295515
Potential fix for pull request finding
cipheraxat Jul 19, 2026
e9c5dae
Merge branch 'main' into fix/323890-retained-webview-anchor-visibility
cipheraxat Jul 19, 2026
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21 changes: 17 additions & 4 deletions src/vs/workbench/contrib/webview/browser/overlayWebview.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -148,9 +148,12 @@ export class OverlayWebview extends Disposable implements IOverlayWebview {
this._windowId = targetWindow.vscodeWindowId;
this._show(targetWindow);

if (this._anchorState) {
// Only re-apply a still-connected anchor. Unhide happens in `_updateVisibility`
// once a connected anchor is bound (see https://github.com/microsoft/vscode/issues/323890).
if (this._anchorState?.anchorElement.isConnected) {
this.overlayLayout.setAnchorElement(this._anchorState.anchorElement, { clippingContainer: this._anchorState.clippingContainer });
}
this._updateVisibility();

if (oldOwner !== owner) {
const contextKeyService = (scopedContextKeyService || this._baseContextKeyService);
Expand Down Expand Up @@ -200,6 +203,18 @@ export class OverlayWebview extends Disposable implements IOverlayWebview {
this._anchorState = { anchorElement, clippingContainer };
// Force the overlay layout to be created if it doesn't exist
this.overlayLayout.setAnchorElement(anchorElement, { clippingContainer });
this._updateVisibility();
}

private _updateVisibility(): void {
if (!this._overlayLayout) {
return;
}

// Keep retained iframes hidden until a connected CSS anchor is bound so they
// do not briefly paint at the browser default size (~300×150).
const shouldShow = !!this._owner && !!this._anchorState?.anchorElement.isConnected;
this._overlayLayout.content.style.visibility = shouldShow ? 'visible' : 'hidden';
}

private _show(targetWindow: CodeWindow) {
Expand Down Expand Up @@ -274,9 +289,7 @@ export class OverlayWebview extends Disposable implements IOverlayWebview {
this._shouldShowFindWidgetOnRestore = false;
}

if (this._overlayLayout) {
this._overlayLayout.content.style.visibility = 'visible';
}
// Visibility is updated only after a connected CSS anchor has been bound (#323890).
}

public setHtml(html: string) {
Expand Down
14 changes: 9 additions & 5 deletions src/vs/workbench/contrib/webviewPanel/browser/webviewEditor.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -161,18 +161,22 @@ export class WebviewEditor extends EditorPane {
}

private claimWebview(input: WebviewInput): void {
// Check if this editor is inside a modal editor
const modalEditorContainer = this._editorGroupsService.activeModalEditorPart?.modalElement;
const isModal = isHTMLElement(modalEditorContainer) && this._element && modalEditorContainer.contains(this._element);
this._clippingContainer = isModal ? undefined : this._workbenchLayoutService.getContainer(this.window, Parts.EDITOR_PART);

// Bind the CSS anchor before claim when the editor element is already connected
// so retained webviews size correctly on first paint (#323890).
this.setWebviewAnchorElement(input.webview);

input.claim(this, this.window, this.scopedContextKeyService);

if (this._element) {
this._element.setAttribute('aria-flowto', input.webview.container.id);
DOM.setParentFlowTo(input.webview.container, this._element);
}

// Check if this editor is inside a modal editor
const modalEditorContainer = this._editorGroupsService.activeModalEditorPart?.modalElement;
const isModal = isHTMLElement(modalEditorContainer) && this._element && modalEditorContainer.contains(this._element);
this._clippingContainer = isModal ? undefined : this._workbenchLayoutService.getContainer(this.window, Parts.EDITOR_PART);

this._webviewVisibleDisposables.clear();

// Webviews are not part of the normal editor dom, so we have to register our own drag and drop handler on them.
Expand Down