71 lines
2.1 KiB
TypeScript
71 lines
2.1 KiB
TypeScript
/*---------------------------------------------------------------------------------------------
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* Copyright (c) Microsoft Corporation. All rights reserved.
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* Licensed under the MIT License. See License.txt in the project root for license information.
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*--------------------------------------------------------------------------------------------*/
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import * as vscode from 'vscode';
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import { Disposable } from '../util/dispose';
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import { isMarkdownFile } from './file';
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export class TopmostLineMonitor extends Disposable {
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private readonly pendingUpdates = new Map<string, number>();
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private readonly throttle = 50;
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constructor() {
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super();
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this._register(vscode.window.onDidChangeTextEditorVisibleRanges(event => {
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if (isMarkdownFile(event.textEditor.document)) {
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const line = getVisibleLine(event.textEditor);
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if (typeof line === 'number') {
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this.updateLine(event.textEditor.document.uri, line);
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}
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}
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}));
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}
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private readonly _onChanged = this._register(new vscode.EventEmitter<{ readonly resource: vscode.Uri, readonly line: number }>());
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public readonly onDidChanged = this._onChanged.event;
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private updateLine(
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resource: vscode.Uri,
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line: number
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) {
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const key = resource.toString();
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if (!this.pendingUpdates.has(key)) {
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// schedule update
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setTimeout(() => {
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if (this.pendingUpdates.has(key)) {
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this._onChanged.fire({
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resource,
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line: this.pendingUpdates.get(key) as number
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});
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this.pendingUpdates.delete(key);
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}
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}, this.throttle);
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}
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this.pendingUpdates.set(key, line);
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}
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}
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/**
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* Get the top-most visible range of `editor`.
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*
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* Returns a fractional line number based the visible character within the line.
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* Floor to get real line number
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*/
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export function getVisibleLine(
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editor: vscode.TextEditor
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): number | undefined {
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if (!editor.visibleRanges.length) {
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return undefined;
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}
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const firstVisiblePosition = editor.visibleRanges[0].start;
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const lineNumber = firstVisiblePosition.line;
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const line = editor.document.lineAt(lineNumber);
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const progress = firstVisiblePosition.character / (line.text.length + 2);
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return lineNumber + progress;
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}
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