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import { Type } from "typebox";
import { type Result, err, ok } from "../util/result";
import { defineBrowserTool, type ToolErr, type ToolOk } from "../util/tool";
import { cdpCall } from "./cdp-call";
const ScrollArgs = Type.Object({
x: Type.Optional(Type.Number({ description: "X coordinate where to scroll. Default: viewport center" })),
y: Type.Optional(Type.Number({ description: "Y coordinate where to scroll. Default: viewport center" })),
deltaX: Type.Optional(Type.Number({ default: 0, description: "Horizontal scroll delta (CSS pixels). Positive = right." })),
deltaY: Type.Optional(Type.Number({
default: 300,
description: "Vertical scroll delta (CSS pixels). Positive = down, negative = up (W3C wheel-event convention). Default: 300 (scroll down).",
})),
});
export const scrollTool = defineBrowserTool({
name: "browser_scroll",
label: "Browser Scroll",
description:
"Scroll the page at given coordinates. deltaY follows W3C wheel-event convention: positive = scroll down, negative = scroll up. Default scrolls down (deltaY = 300).",
promptSnippet: "Scroll the page (deltaY positive=down, negative=up)",
promptGuidelines: [
"Pass x/y to target a specific scrollable region (e.g., a div with overflow); otherwise scrolls the page at viewport center.",
],
parameters: ScrollArgs,
concurrency: "serialized",
async handler(args, { client }): Promise<Result<ToolOk, ToolErr>> {
const info = await client.pageInfo();
if (!info.success) return err({ kind: "cdp_error", message: info.error.message });
if ("dialog" in info.data) {
return err({
kind: "invalid_state",
message: `Dialog open: ${info.data.dialog.type} — ${info.data.dialog.message}`,
});
}
const cx = args.x ?? Math.round(info.data.width / 2);
const cy = args.y ?? Math.round(info.data.height / 2);
const dx = args.deltaX ?? 0;
const dy = args.deltaY ?? 300;
// The page target must be focused or Input events are dropped silently: mouseWheel hangs and synthesizeScrollGesture returns ok without scrolling.
const front = await cdpCall(client, "Page.bringToFront", {});
if (!front.success) return front;
// Establish compositor mouse position first, or CDP sometimes drops the wheel event with a timeout.
const moved = await cdpCall(client, "Input.dispatchMouseEvent", {
type: "mouseMoved", x: cx, y: cy, button: "none", buttons: 0,
});
if (!moved.success) return moved;
const wheel = await cdpCall(client, "Input.dispatchMouseEvent", {
type: "mouseWheel", x: cx, y: cy, deltaX: dx, deltaY: dy,
button: "none", buttons: 0, pointerType: "mouse",
});
if (!wheel.success) return wheel;
return ok({
text: `Scrolled at (${cx}, ${cy}) by (${dx}, ${dy})`,
details: { x: cx, y: cy, deltaX: dx, deltaY: dy },
});
},
});
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