code-server/lib/vscode/extensions/markdown-language-features/preview-src/scroll-sync.ts

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/*---------------------------------------------------------------------------------------------
* Copyright (c) Microsoft Corporation. All rights reserved.
* Licensed under the MIT License. See License.txt in the project root for license information.
*--------------------------------------------------------------------------------------------*/
import { getSettings } from './settings';
const codeLineClass = 'code-line';
function clamp(min: number, max: number, value: number) {
return Math.min(max, Math.max(min, value));
}
function clampLine(line: number) {
return clamp(0, getSettings().lineCount - 1, line);
}
export interface CodeLineElement {
element: HTMLElement;
line: number;
}
const getCodeLineElements = (() => {
let elements: CodeLineElement[];
return () => {
if (!elements) {
elements = [{ element: document.body, line: 0 }];
for (const element of document.getElementsByClassName(codeLineClass)) {
const line = +element.getAttribute('data-line')!;
if (isNaN(line)) {
continue;
}
if (element.tagName === 'CODE' && element.parentElement && element.parentElement.tagName === 'PRE') {
// Fenched code blocks are a special case since the `code-line` can only be marked on
// the `<code>` element and not the parent `<pre>` element.
elements.push({ element: element.parentElement as HTMLElement, line });
} else {
elements.push({ element: element as HTMLElement, line });
}
}
}
return elements;
};
})();
/**
* Find the html elements that map to a specific target line in the editor.
*
* If an exact match, returns a single element. If the line is between elements,
* returns the element prior to and the element after the given line.
*/
export function getElementsForSourceLine(targetLine: number): { previous: CodeLineElement; next?: CodeLineElement; } {
const lineNumber = Math.floor(targetLine);
const lines = getCodeLineElements();
let previous = lines[0] || null;
for (const entry of lines) {
if (entry.line === lineNumber) {
return { previous: entry, next: undefined };
} else if (entry.line > lineNumber) {
return { previous, next: entry };
}
previous = entry;
}
return { previous };
}
/**
* Find the html elements that are at a specific pixel offset on the page.
*/
export function getLineElementsAtPageOffset(offset: number): { previous: CodeLineElement; next?: CodeLineElement; } {
const lines = getCodeLineElements();
const position = offset - window.scrollY;
let lo = -1;
let hi = lines.length - 1;
while (lo + 1 < hi) {
const mid = Math.floor((lo + hi) / 2);
const bounds = getElementBounds(lines[mid]);
if (bounds.top + bounds.height >= position) {
hi = mid;
}
else {
lo = mid;
}
}
const hiElement = lines[hi];
const hiBounds = getElementBounds(hiElement);
if (hi >= 1 && hiBounds.top > position) {
const loElement = lines[lo];
return { previous: loElement, next: hiElement };
}
if (hi > 1 && hi < lines.length && hiBounds.top + hiBounds.height > position) {
return { previous: hiElement, next: lines[hi + 1] };
}
return { previous: hiElement };
}
function getElementBounds({ element }: CodeLineElement): { top: number, height: number } {
const myBounds = element.getBoundingClientRect();
// Some code line elements may contain other code line elements.
// In those cases, only take the height up to that child.
const codeLineChild = element.querySelector(`.${codeLineClass}`);
if (codeLineChild) {
const childBounds = codeLineChild.getBoundingClientRect();
const height = Math.max(1, (childBounds.top - myBounds.top));
return {
top: myBounds.top,
height: height
};
}
return myBounds;
}
/**
* Attempt to reveal the element for a source line in the editor.
*/
export function scrollToRevealSourceLine(line: number) {
if (!getSettings().scrollPreviewWithEditor) {
return;
}
if (line <= 0) {
window.scroll(window.scrollX, 0);
return;
}
const { previous, next } = getElementsForSourceLine(line);
if (!previous) {
return;
}
let scrollTo = 0;
const rect = getElementBounds(previous);
const previousTop = rect.top;
if (next && next.line !== previous.line) {
// Between two elements. Go to percentage offset between them.
const betweenProgress = (line - previous.line) / (next.line - previous.line);
const elementOffset = next.element.getBoundingClientRect().top - previousTop;
scrollTo = previousTop + betweenProgress * elementOffset;
} else {
const progressInElement = line - Math.floor(line);
scrollTo = previousTop + (rect.height * progressInElement);
}
window.scroll(window.scrollX, Math.max(1, window.scrollY + scrollTo));
}
export function getEditorLineNumberForPageOffset(offset: number) {
const { previous, next } = getLineElementsAtPageOffset(offset);
if (previous) {
const previousBounds = getElementBounds(previous);
const offsetFromPrevious = (offset - window.scrollY - previousBounds.top);
if (next) {
const progressBetweenElements = offsetFromPrevious / (getElementBounds(next).top - previousBounds.top);
const line = previous.line + progressBetweenElements * (next.line - previous.line);
return clampLine(line);
} else {
const progressWithinElement = offsetFromPrevious / (previousBounds.height);
const line = previous.line + progressWithinElement;
return clampLine(line);
}
}
return null;
}
/**
* Try to find the html element by using a fragment id
*/
export function getLineElementForFragment(fragment: string): CodeLineElement | undefined {
return getCodeLineElements().find((element) => {
return element.element.id === fragment;
});
}