Empty hidden editors

packages/core/src/browser/widgets/widget.ts

@@ -225,14 +225,18 @@ export class BaseWidget extends Widget implements PreviewableWidget {
     override setFlag(flag: Widget.Flag): void {
         super.setFlag(flag);
         if (flag === Widget.Flag.IsVisible) {
-            this.onDidChangeVisibilityEmitter.fire(this.isVisible);
+            this.handleVisiblityChanged(this.isVisible);
         }
     }
 
+    protected handleVisiblityChanged(isNowVisible: boolean): void {
+        this.onDidChangeVisibilityEmitter.fire(isNowVisible);
+    }
+
     override clearFlag(flag: Widget.Flag): void {
         super.clearFlag(flag);
         if (flag === Widget.Flag.IsVisible) {
-            this.onDidChangeVisibilityEmitter.fire(this.isVisible);
+            this.handleVisiblityChanged(this.isVisible);
         }
     }
 }

packages/editor/src/browser/editor-widget.ts

@@ -60,6 +60,11 @@ export class EditorWidget extends BaseWidget implements SaveableSource, Navigata
         }
     }
 
+    protected override handleVisiblityChanged(isNowVisible: boolean): void {
+        this.editor.handleVisibilityChanged(isNowVisible);
+        super.handleVisiblityChanged(isNowVisible);
+    }
+
     get saveable(): Saveable {
         return this.editor.document;
     }

packages/editor/src/browser/editor.ts

@@ -295,6 +295,8 @@ export interface TextEditor extends Disposable, TextEditorSelection, Navigatable
     readonly onEncodingChanged: Event<string>;
 
     shouldDisplayDirtyDiff(): boolean;
+
+    handleVisibilityChanged(nowVisible: boolean): void;
 }
 
 export interface Selection extends Range {

packages/monaco/src/browser/monaco-editor-provider.ts

@@ -48,7 +48,7 @@ import { MarkdownString } from '@theia/core/lib/common/markdown-rendering';
 export const MonacoEditorFactory = Symbol('MonacoEditorFactory');
 export interface MonacoEditorFactory {
     readonly scheme: string;
-    create(model: MonacoEditorModel, defaultOptions: MonacoEditor.IOptions, defaultOverrides: EditorServiceOverrides): MonacoEditor;
+    create(model: MonacoEditorModel, defaultOptions: MonacoEditor.IOptions, defaultOverrides: EditorServiceOverrides): Promise<MonacoEditor>;
 }
 
 @injectable()
@@ -198,8 +198,8 @@ export class MonacoEditorProvider {
         const options = this.createMonacoEditorOptions(model);
         const factory = this.factories.getContributions().find(({ scheme }) => uri.scheme === scheme);
         const editor = factory
-            ? factory.create(model, options, override)
-            : new MonacoEditor(uri, model, document.createElement('div'), this.services, options, override);
+            ? await factory.create(model, options, override)
+            : await MonacoEditor.create(uri, model, document.createElement('div'), this.services, options, override);
         toDispose.push(this.editorPreferences.onPreferenceChanged(event => {
             if (event.affects(uri.toString(), model.languageId)) {
                 this.updateMonacoEditorOptions(editor, event);
@@ -380,7 +380,7 @@ export class MonacoEditorProvider {
             }, this.m2p, this.p2m);
             toDispose.push(document);
             const model = (await document.load()).textEditorModel;
-            return new MonacoEditor(
+            return await MonacoEditor.create(
                 uri,
                 document,
                 node,

packages/monaco/src/browser/monaco-editor.ts

@@ -64,6 +64,7 @@ import { ILanguageFeaturesService } from '@theia/monaco-editor-core/esm/vs/edito
 import * as objects from '@theia/monaco-editor-core/esm/vs/base/common/objects';
 import { Selection } from '@theia/editor/lib/browser/editor';
 import { IHoverService } from '@theia/monaco-editor-core/esm/vs/platform/hover/browser/hover';
+import { MonacoTextModelService } from './monaco-text-model-service';
 
 export type ServicePair<T> = [ServiceIdentifier<T>, T];
 
@@ -81,13 +82,28 @@ export class MonacoEditorServices {
     @inject(ContextKeyService)
     protected readonly contextKeyService: ContextKeyService;
 
+    @inject(MonacoTextModelService)
+    protected readonly monacoModelService: MonacoTextModelService;
+
     constructor(@unmanaged() services: MonacoEditorServices) {
         Object.assign(this, services);
     }
 }
 
 export class MonacoEditor extends MonacoEditorServices implements TextEditor {
 
+    static async create(uri: URI,
+        document: MonacoEditorModel,
+        node: HTMLElement,
+        services: MonacoEditorServices,
+        options?: MonacoEditor.IOptions,
+        override?: EditorServiceOverrides,
+        parentEditor?: MonacoEditor): Promise<MonacoEditor> {
+        const instance = new MonacoEditor(uri, document, node, services, options, override, parentEditor);
+        await instance.init();
+        return instance;
+    }
+
     protected readonly toDispose = new DisposableCollection();
 
     protected readonly autoSizing: boolean;
@@ -109,8 +125,10 @@ export class MonacoEditor extends MonacoEditorServices implements TextEditor {
     readonly onDidResize = this.onResizeEmitter.event;
 
     readonly documents = new Set<MonacoEditorModel>();
+    protected model: monaco.editor.ITextModel | null;
+    savedViewState: monaco.editor.ICodeEditorViewState | null;
 
-    constructor(
+    protected constructor(
         readonly uri: URI,
         readonly document: MonacoEditorModel,
         readonly node: HTMLElement,
@@ -140,6 +158,10 @@ export class MonacoEditor extends MonacoEditorServices implements TextEditor {
         this.addHandlers(this.editor);
     }
 
+    protected async init(): Promise<void> {
+        this.toDispose.push(await this.monacoModelService.createModelReference(this.uri));
+    }
+
     getEncoding(): string {
         return this.document.getEncoding() || UTF8;
     }
@@ -228,6 +250,22 @@ export class MonacoEditor extends MonacoEditorServices implements TextEditor {
         }));
     }
 
+    handleVisibilityChanged(nowVisible: boolean): void {
+        if (nowVisible) {
+            if (this.model) {
+                this.editor.setModel(this.model);
+                this.editor.restoreViewState(this.savedViewState);
+                this.editor.focus();
+            }
+        } else {
+            this.model = this.editor.getModel();
+            this.savedViewState = this.editor.saveViewState();
+
+            // eslint-disable-next-line no-null/no-null
+            this.editor.setModel(null); // workaround for https://github.com/eclipse-theia/theia/issues/14880
+        }
+    }
+
     getVisibleRanges(): Range[] {
         return this.editor.getVisibleRanges().map(range => this.m2p.asRange(range));
     }

packages/monaco/src/browser/monaco-to-protocol-converter.ts

@@ -69,7 +69,14 @@ export class MonacoToProtocolConverter {
         }
     }
 
-    asSelection(selection: monaco.Selection): Selection {
+    asSelection(selection: monaco.Selection | null): Selection {
+        if (!selection) {
+            return {
+                start: { line: 0, character: 0 },
+                end: { line: 0, character: 0 },
+                direction: 'ltr'
+            };
+        }
         const start = this.asPosition(selection.selectionStartLineNumber, selection.selectionStartColumn);
         const end = this.asPosition(selection.positionLineNumber, selection.positionColumn);
         return {

packages/output/src/browser/output-editor-factory.ts

@@ -35,11 +35,11 @@ export class OutputEditorFactory implements MonacoEditorFactory {
 
     readonly scheme: string = OutputUri.SCHEME;
 
-    create(model: MonacoEditorModel, defaultsOptions: MonacoEditor.IOptions): MonacoEditor {
+    create(model: MonacoEditorModel, defaultsOptions: MonacoEditor.IOptions): Promise<MonacoEditor> {
         const uri = new URI(model.uri);
         const options = this.createOptions(model, defaultsOptions);
         const overrides = this.createOverrides(model);
-        return new MonacoEditor(uri, model, document.createElement('div'), this.services, options, overrides);
+        return MonacoEditor.create(uri, model, document.createElement('div'), this.services, options, overrides);
     }
 
     protected createOptions(model: MonacoEditorModel, defaultOptions: MonacoEditor.IOptions): MonacoEditor.IOptions {