add scale factor to set viewport for retina screenshots (#691)

* device scale

* fix node.js daemon

* fix cargo fmt formatting for scale factor code

* fixes

README.md

@@ -197,7 +197,7 @@ agent-browser mouse wheel <dy> [dx]   # Scroll wheel
 ### Browser Settings
 
 ```bash
-agent-browser set viewport <w> <h>    # Set viewport size
+agent-browser set viewport <w> <h> [scale]  # Set viewport size (scale for retina, e.g. 2)
 agent-browser set device <name>       # Emulate device ("iPhone 14")
 agent-browser set geo <lat> <lng>     # Set geolocation
 agent-browser set offline [on|off]    # Toggle offline mode

cli/src/commands.rs

@@ -1871,25 +1871,35 @@ fn parse_set(rest: &[&str], id: &str) -> Result<Value, ParseError> {
         Some("viewport") => {
             let w_str = rest.get(1).ok_or_else(|| ParseError::MissingArguments {
                 context: "set viewport".to_string(),
-                usage: "set viewport <width> <height>",
+                usage: "set viewport <width> <height> [scale]",
             })?;
             let h_str = rest.get(2).ok_or_else(|| ParseError::MissingArguments {
                 context: "set viewport".to_string(),
-                usage: "set viewport <width> <height>",
+                usage: "set viewport <width> <height> [scale]",
             })?;
             let w = w_str
                 .parse::<i32>()
                 .map_err(|_| ParseError::MissingArguments {
                     context: "set viewport".to_string(),
-                    usage: "set viewport <width> <height>",
+                    usage: "set viewport <width> <height> [scale]",
                 })?;
             let h = h_str
                 .parse::<i32>()
                 .map_err(|_| ParseError::MissingArguments {
                     context: "set viewport".to_string(),
-                    usage: "set viewport <width> <height>",
+                    usage: "set viewport <width> <height> [scale]",
                 })?;
-            Ok(json!({ "id": id, "action": "viewport", "width": w, "height": h }))
+            let mut cmd = json!({ "id": id, "action": "viewport", "width": w, "height": h });
+            if let Some(scale_str) = rest.get(3) {
+                let scale = scale_str
+                    .parse::<f64>()
+                    .map_err(|_| ParseError::MissingArguments {
+                        context: "set viewport".to_string(),
+                        usage: "set viewport <width> <height> [scale]",
+                    })?;
+                cmd["deviceScaleFactor"] = json!(scale);
+            }
+            Ok(cmd)
         }
         Some("device") => {
             let dev = rest.get(1).ok_or_else(|| ParseError::MissingArguments {
@@ -3045,6 +3055,45 @@ mod tests {
         assert_eq!(cmd["reducedMotion"], "reduce");
     }
 
+    #[test]
+    fn test_set_viewport() {
+        let cmd = parse_command(&args("set viewport 1920 1080"), &default_flags()).unwrap();
+        assert_eq!(cmd["action"], "viewport");
+        assert_eq!(cmd["width"], 1920);
+        assert_eq!(cmd["height"], 1080);
+        assert!(cmd.get("deviceScaleFactor").is_none());
+    }
+
+    #[test]
+    fn test_set_viewport_with_scale() {
+        let cmd = parse_command(&args("set viewport 1920 1080 2"), &default_flags()).unwrap();
+        assert_eq!(cmd["action"], "viewport");
+        assert_eq!(cmd["width"], 1920);
+        assert_eq!(cmd["height"], 1080);
+        assert_eq!(cmd["deviceScaleFactor"], 2.0);
+    }
+
+    #[test]
+    fn test_set_viewport_with_fractional_scale() {
+        let cmd = parse_command(&args("set viewport 375 812 3"), &default_flags()).unwrap();
+        assert_eq!(cmd["action"], "viewport");
+        assert_eq!(cmd["width"], 375);
+        assert_eq!(cmd["height"], 812);
+        assert_eq!(cmd["deviceScaleFactor"], 3.0);
+    }
+
+    #[test]
+    fn test_set_viewport_missing_height() {
+        let result = parse_command(&args("set viewport 1920"), &default_flags());
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_set_viewport_invalid_scale() {
+        let result = parse_command(&args("set viewport 1920 1080 abc"), &default_flags());
+        assert!(result.is_err());
+    }
+
     #[test]
     fn test_find_first_no_value() {
         let cmd = parse_command(&args("find first a click"), &default_flags()).unwrap();

cli/src/native/e2e_tests.rs

@@ -777,6 +777,77 @@ async fn e2e_wait() {
     assert_success(&resp);
 }
 
+// ---------------------------------------------------------------------------
+// Viewport with deviceScaleFactor (retina)
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+#[ignore]
+async fn e2e_viewport_scale_factor() {
+    let mut state = DaemonState::new();
+
+    let resp = execute_command(
+        &json!({ "id": "1", "action": "launch", "headless": true }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+
+    let resp = execute_command(
+        &json!({ "id": "2", "action": "navigate", "url": "about:blank" }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+
+    // Default devicePixelRatio should be 1
+    let resp = execute_command(
+        &json!({ "id": "3", "action": "evaluate", "script": "window.devicePixelRatio" }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+    let default_dpr = get_data(&resp)["result"].as_f64().unwrap();
+    assert_eq!(default_dpr, 1.0, "Default devicePixelRatio should be 1");
+
+    // Set viewport with 2x scale factor
+    let resp = execute_command(
+        &json!({ "id": "4", "action": "viewport", "width": 1920, "height": 1080, "deviceScaleFactor": 2.0 }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+    assert_eq!(get_data(&resp)["width"], 1920);
+    assert_eq!(get_data(&resp)["height"], 1080);
+    assert_eq!(get_data(&resp)["deviceScaleFactor"], 2.0);
+
+    // devicePixelRatio should now be 2
+    let resp = execute_command(
+        &json!({ "id": "5", "action": "evaluate", "script": "window.devicePixelRatio" }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+    let new_dpr = get_data(&resp)["result"].as_f64().unwrap();
+    assert_eq!(
+        new_dpr, 2.0,
+        "devicePixelRatio should be 2 after setting scale factor"
+    );
+
+    // CSS viewport width should still be 1920 (not 3840)
+    let resp = execute_command(
+        &json!({ "id": "6", "action": "evaluate", "script": "window.innerWidth" }),
+        &mut state,
+    )
+    .await;
+    assert_success(&resp);
+    let css_width = get_data(&resp)["result"].as_i64().unwrap();
+    assert_eq!(css_width, 1920, "CSS width should remain 1920 at 2x scale");
+
+    let resp = execute_command(&json!({ "id": "99", "action": "close" }), &mut state).await;
+    assert_success(&resp);
+}
+
 // ---------------------------------------------------------------------------
 // Viewport and emulation
 // ---------------------------------------------------------------------------

cli/src/output.rs

@@ -1590,7 +1590,7 @@ Usage: agent-browser set <setting> [args]
 Configures various browser settings and emulation options.
 
 Settings:
-  viewport <w> <h>           Set viewport size
+  viewport <w> <h> [scale]   Set viewport size (scale = deviceScaleFactor, e.g. 2 for retina)
   device <name>              Emulate device (e.g., "iPhone 12")
   geo <lat> <lng>            Set geolocation
   offline [on|off]           Toggle offline mode
@@ -1605,6 +1605,7 @@ Global Options:
 
 Examples:
   agent-browser set viewport 1920 1080
+  agent-browser set viewport 1920 1080 2    # 2x retina
   agent-browser set device "iPhone 12"
   agent-browser set geo 37.7749 -122.4194
   agent-browser set offline on

docs/src/app/commands/page.mdx

@@ -123,7 +123,7 @@ agent-browser mouse wheel <dy> [dx]   # Scroll wheel
 ## Settings
 
 ```bash
-agent-browser set viewport <w> <h>    # Set viewport size
+agent-browser set viewport <w> <h> [scale]  # Set viewport size (scale for retina, e.g. 2)
 agent-browser set device <name>       # Emulate device ("iPhone 14")
 agent-browser set geo <lat> <lng>     # Set geolocation
 agent-browser set offline [on|off]    # Toggle offline mode

skills/agent-browser/references/commands.md

@@ -129,6 +129,7 @@ agent-browser find nth 2 "a" hover
 
 ```bash
 agent-browser set viewport 1920 1080          # Set viewport size
+agent-browser set viewport 1920 1080 2        # 2x retina (same CSS size, higher res screenshots)
 agent-browser set device "iPhone 14"          # Emulate device
 agent-browser set geo 37.7749 -122.4194       # Set geolocation (alias: geolocation)
 agent-browser set offline on                  # Toggle offline mode

src/actions.ts

@@ -1465,11 +1465,33 @@ async function handleViewport(
   command: ViewportCommand,
   browser: BrowserManager
 ): Promise<Response> {
-  await browser.setViewport(command.width, command.height);
+  if (command.deviceScaleFactor && command.deviceScaleFactor !== 1) {
-  return successResponse(command.id, {
+    await browser.setViewport(command.width, command.height);
+    await browser.setDeviceScaleFactor(
+      command.deviceScaleFactor,
+      command.width,
+      command.height,
+      false
+    );
+  } else {
+    // deviceScaleFactor is 1 or undefined -- clear any previously-set CDP
+    // Emulation.setDeviceMetricsOverride so stale DPR doesn't persist.
+    try {
+      await browser.clearDeviceMetricsOverride();
+    } catch {
+      // Ignore if override was never set
+    }
+    await browser.setViewport(command.width, command.height);
+  }
+
+  const result: Record<string, unknown> = {
     width: command.width,
     height: command.height,
-  });
+  };
+  if (command.deviceScaleFactor !== undefined) {
+    result.deviceScaleFactor = command.deviceScaleFactor;
+  }
+  return successResponse(command.id, result);
 }
 
 async function handleUserAgent(

src/protocol.ts

@@ -270,6 +270,7 @@ const viewportSchema = baseCommandSchema.extend({
   action: z.literal('viewport'),
   width: z.number().positive(),
   height: z.number().positive(),
+  deviceScaleFactor: z.number().positive().optional(),
 });
 
 const userAgentSchema = baseCommandSchema.extend({

src/types.ts

@@ -263,6 +263,7 @@ export interface ViewportCommand extends BaseCommand {
   action: 'viewport';
   width: number;
   height: number;
+  deviceScaleFactor?: number;
 }
 
 // User agent