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2026-07-13 12:30:05 +08:00

454 lines
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TypeScript

/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import assert from 'node:assert';
import {rm, stat, mkdir, chmod, writeFile} from 'node:fs/promises';
import {tmpdir} from 'node:os';
import {join} from 'node:path';
import {describe, it} from 'node:test';
import type {ParsedArguments} from '../../src/bin/chrome-devtools-mcp-cli-options.js';
import {TextSnapshot} from '../../src/TextSnapshot.js';
import {screenshot} from '../../src/tools/screenshot.js';
import {screenshots} from '../snapshot.js';
import {html, withMcpContext} from '../utils.js';
const screenshotTool = screenshot({} as ParsedArguments);
/**
* Reads the pixel width from a PNG buffer's IHDR chunk (bytes 16..19).
*/
function pngWidth(data: Buffer): number {
return data.readUInt32BE(16);
}
/**
* Reads the pixel height from a PNG buffer's IHDR chunk (bytes 20..23).
*/
function pngHeight(data: Buffer): number {
return data.readUInt32BE(20);
}
describe('screenshot', () => {
describe('browser_take_screenshot', () => {
it('with default options', async () => {
await withMcpContext(async (response, context) => {
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await screenshotTool.handler(
{params: {format: 'png'}, page: context.getSelectedMcpPage()},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/png');
assert.equal(
response.responseLines.at(0),
"Took a screenshot of the current page's viewport.",
);
});
});
it('ignores quality', async () => {
await withMcpContext(async (response, context) => {
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await screenshotTool.handler(
{
params: {format: 'png', quality: 0},
page: context.getSelectedMcpPage(),
},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/png');
assert.equal(
response.responseLines.at(0),
"Took a screenshot of the current page's viewport.",
);
});
});
it('with jpeg', async () => {
await withMcpContext(async (response, context) => {
await screenshotTool.handler(
{params: {format: 'jpeg'}, page: context.getSelectedMcpPage()},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/jpeg');
assert.equal(
response.responseLines.at(0),
"Took a screenshot of the current page's viewport.",
);
});
});
it('with webp', async () => {
await withMcpContext(async (response, context) => {
await screenshotTool.handler(
{params: {format: 'webp'}, page: context.getSelectedMcpPage()},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/webp');
assert.equal(
response.responseLines.at(0),
"Took a screenshot of the current page's viewport.",
);
});
});
it('with full page', async () => {
await withMcpContext(async (response, context) => {
const fixture = screenshots.viewportOverflow;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await screenshotTool.handler(
{
params: {format: 'png', fullPage: true},
page: context.getSelectedMcpPage(),
},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/png');
assert.equal(
response.responseLines.at(0),
'Took a screenshot of the full current page.',
);
});
});
it('with full page resulting in a large screenshot', async () => {
await withMcpContext(async (response, context) => {
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(
html`${`<div style="color:blue;">test</div>`.repeat(6500)}
<div
id="red"
style="color:blue;"
>test</div
> `,
);
await page.evaluate(() => {
const el = document.querySelector('#red');
return el?.scrollIntoViewIfNeeded();
});
await screenshotTool.handler(
{
params: {format: 'png', fullPage: true},
page: context.getSelectedMcpPage(),
},
response,
context,
);
assert.equal(response.images.length, 0);
assert.equal(
response.responseLines.at(0),
'Took a screenshot of the full current page.',
);
assert.ok(
response.responseLines.at(1)?.match(/Saved screenshot to.*\.png/),
);
});
});
it('with element uid', async () => {
await withMcpContext(async (response, context) => {
const fixture = screenshots.button;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
context.getSelectedMcpPage().textSnapshot = await TextSnapshot.create(
context.getSelectedMcpPage(),
);
await screenshotTool.handler(
{
params: {
format: 'png',
uid: '1_1',
},
page: context.getSelectedMcpPage(),
},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/png');
assert.equal(
response.responseLines.at(0),
'Took a screenshot of node with uid "1_1".',
);
});
});
it('with filePath', async () => {
await withMcpContext(async (response, context) => {
const filePath = join(tmpdir(), 'test-screenshot.png');
try {
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await screenshotTool.handler(
{
params: {format: 'png', filePath},
page: context.getSelectedMcpPage(),
},
response,
context,
);
assert.equal(response.images.length, 0);
assert.equal(
response.responseLines.at(0),
"Took a screenshot of the current page's viewport.",
);
assert.equal(
response.responseLines.at(1),
`Saved screenshot to ${filePath}.`,
);
const stats = await stat(filePath);
assert.ok(stats.isFile());
assert.ok(stats.size > 0);
} finally {
await rm(filePath, {force: true});
}
});
});
it('with unwritable filePath', async () => {
if (process.platform === 'win32') {
const filePath = join(
tmpdir(),
'readonly-file-for-screenshot-test.png',
);
// Create the file and make it read-only.
await writeFile(filePath, '');
await chmod(filePath, 0o400);
try {
await withMcpContext(async (response, context) => {
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await assert.rejects(
screenshotTool.handler(
{
params: {format: 'png', filePath},
page: context.getSelectedMcpPage(),
},
response,
context,
),
);
});
} finally {
// Make the file writable again so it can be deleted.
await chmod(filePath, 0o600);
await rm(filePath, {force: true});
}
} else {
const dir = join(tmpdir(), 'readonly-dir-for-screenshot-test');
await mkdir(dir, {recursive: true});
await chmod(dir, 0o500);
const filePath = join(dir, 'test-screenshot.png');
try {
await withMcpContext(async (response, context) => {
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await assert.rejects(
screenshotTool.handler(
{
params: {format: 'png', filePath},
page: context.getSelectedMcpPage(),
},
response,
context,
),
);
});
} finally {
await chmod(dir, 0o700);
await rm(dir, {recursive: true, force: true});
}
}
});
it('honors screenshotFormat default from CLI args', async () => {
const tool = screenshot({
screenshotFormat: 'jpeg',
} as ParsedArguments);
await withMcpContext(async (response, context) => {
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
// No explicit format passed: zod should apply the CLI-driven default.
await tool.handler(
{
params: {format: tool.schema.format.parse(undefined)},
page: context.getSelectedMcpPage(),
},
response,
context,
);
assert.equal(response.images.length, 1);
assert.equal(response.images[0].mimeType, 'image/jpeg');
});
});
it('keeps "png" as default format when no CLI override is set', async () => {
const tool = screenshot({} as ParsedArguments);
assert.equal(tool.schema.format.parse(undefined), 'png');
});
it('downscales viewport screenshot when screenshotMaxWidth is set', async () => {
const tool = screenshot({
screenshotMaxWidth: 100,
} as ParsedArguments);
await withMcpContext(async (response, context) => {
const page = context.getSelectedMcpPage().pptrPage;
await page.setViewport({width: 800, height: 600});
await page.setContent(
html`<div style="width:100vw;height:100vh;background:red"></div>`,
);
await tool.handler(
{params: {format: 'png'}, page: context.getSelectedMcpPage()},
response,
context,
);
assert.equal(response.images.length, 1);
const buf = Buffer.from(response.images[0].data, 'base64');
assert.equal(pngWidth(buf), 100);
// Aspect ratio preserved: 800x600 -> 100x75.
assert.equal(pngHeight(buf), 75);
});
});
it('downscales using the smaller scale when both max-width and max-height are set', async () => {
const tool = screenshot({
screenshotMaxWidth: 400,
screenshotMaxHeight: 60,
} as ParsedArguments);
await withMcpContext(async (response, context) => {
const page = context.getSelectedMcpPage().pptrPage;
await page.setViewport({width: 800, height: 600});
await page.setContent(
html`<div style="width:100vw;height:100vh"></div>`,
);
await tool.handler(
{params: {format: 'png'}, page: context.getSelectedMcpPage()},
response,
context,
);
const buf = Buffer.from(response.images[0].data, 'base64');
// height bound dictates: 60/600 = 0.1 -> 80x60.
assert.equal(pngHeight(buf), 60);
assert.equal(pngWidth(buf), 80);
});
});
it('does not resize when source is smaller than the max bounds', async () => {
const tool = screenshot({
screenshotMaxWidth: 4000,
screenshotMaxHeight: 4000,
} as ParsedArguments);
await withMcpContext(async (response, context) => {
const page = context.getSelectedMcpPage().pptrPage;
await page.setViewport({width: 800, height: 600});
await page.setContent(html`<div></div>`);
await tool.handler(
{params: {format: 'png'}, page: context.getSelectedMcpPage()},
response,
context,
);
const buf = Buffer.from(response.images[0].data, 'base64');
assert.equal(pngWidth(buf), 800);
assert.equal(pngHeight(buf), 600);
});
});
it('downscales full page screenshot when screenshotMaxWidth is set', async () => {
const tool = screenshot({
screenshotMaxWidth: 200,
} as ParsedArguments);
await withMcpContext(async (response, context) => {
const page = context.getSelectedMcpPage().pptrPage;
await page.setViewport({width: 800, height: 600});
await page.setContent(
html`<style>
body {
margin: 0;
}</style
><div style="width:1000px;height:1500px;background:red"></div>`,
);
await tool.handler(
{
params: {format: 'png', fullPage: true},
page: context.getSelectedMcpPage(),
},
response,
context,
);
const buf = Buffer.from(response.images[0].data, 'base64');
// Source is at least 1000x1500; scale = 200/1000 = 0.2 -> ~200x300.
// Allow ±2px to absorb sub-pixel rasterization rounding by Chrome.
assert.equal(pngWidth(buf), 200);
assert.ok(
Math.abs(pngHeight(buf) - 300) <= 2,
`expected height near 300, got ${pngHeight(buf)}`,
);
});
});
it('with malformed filePath', async () => {
await withMcpContext(async (response, context) => {
// Use a platform-specific invalid character.
// On Windows, characters like '<', '>', ':', '"', '/', '\', '|', '?', '*' are invalid.
// On POSIX, the null byte is invalid.
const invalidChar = process.platform === 'win32' ? '>' : '\0';
const filePath = `malformed${invalidChar}path.png`;
const fixture = screenshots.basic;
const page = context.getSelectedMcpPage().pptrPage;
await page.setContent(fixture.html);
await assert.rejects(
screenshotTool.handler(
{
params: {format: 'png', filePath},
page: context.getSelectedMcpPage(),
},
response,
context,
),
);
});
});
});
});