[java][bidi] Add browsing context's capture box screenshot command

Author: pujagani

java/src/org/openqa/selenium/bidi/browsingcontext/BrowsingContext.java

@@ -226,6 +226,24 @@ public String captureScreenshot() {
             }));
   }
 
+  public String captureBoxScreenshot(double x, double y, double width, double height) {
+    return this.bidi.send(
+      new Command<>(
+        "browsingContext.captureScreenshot",
+        ImmutableMap.of(CONTEXT, id,
+                        "clip", ImmutableMap.of(
+                        "type", "viewport",
+                        "x", x,
+                        "y", y,
+                        "width", width,
+                        "height", height
+          )),
+        jsonInput -> {
+          Map<String, Object> result = jsonInput.read(Map.class);
+          return (String) result.get("data");
+        }));
+  }
+
   public void close() {
     // This might need more clean up actions once the behavior is defined.
     // Specially when last tab or window is closed.

java/test/org/openqa/selenium/bidi/browsingcontext/BrowsingContextTest.java

@@ -19,6 +19,7 @@
 
 import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
 import static org.assertj.core.api.AssertionsForClassTypes.assertThatExceptionOfType;
+import static org.junit.jupiter.api.Assertions.fail;
 import static org.openqa.selenium.support.ui.ExpectedConditions.alertIsPresent;
 import static org.openqa.selenium.testing.Safely.safelyCall;
 import static org.openqa.selenium.testing.drivers.Browser.CHROME;
@@ -28,10 +29,13 @@
 import static org.openqa.selenium.testing.drivers.Browser.SAFARI;
 
 import java.util.List;
+
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.openqa.selenium.By;
+import org.openqa.selenium.Rectangle;
+import org.openqa.selenium.WebElement;
 import org.openqa.selenium.WindowType;
 import org.openqa.selenium.bidi.BiDiException;
 import org.openqa.selenium.environment.webserver.AppServer;
@@ -74,7 +78,7 @@ void canCreateAWindow() {
   @NotYetImplemented(EDGE)
   void canCreateAWindowWithAReferenceContext() {
     BrowsingContext browsingContext =
-        new BrowsingContext(driver, WindowType.WINDOW, driver.getWindowHandle());
+      new BrowsingContext(driver, WindowType.WINDOW, driver.getWindowHandle());
     assertThat(browsingContext.getId()).isNotEmpty();
   }
 
@@ -93,7 +97,7 @@ void canCreateATab() {
   @NotYetImplemented(EDGE)
   void canCreateATabWithAReferenceContext() {
     BrowsingContext browsingContext =
-        new BrowsingContext(driver, WindowType.TAB, driver.getWindowHandle());
+      new BrowsingContext(driver, WindowType.TAB, driver.getWindowHandle());
     assertThat(browsingContext.getId()).isNotEmpty();
   }
 
@@ -358,6 +362,32 @@ void canCaptureScreenshot() {
     assertThat(screenshot.length()).isPositive();
   }
 
+  @Test
+  @NotYetImplemented(SAFARI)
+  @NotYetImplemented(IE)
+  @NotYetImplemented(CHROME)
+  void canCaptureScreenshotOfViewport() {
+    String expectedBase64EncodedImage =
+      "iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAAVklEQVQYV2P8z8AARIQB41BQOAvomScE/MIElGdcCFS4B"
+      + "8hYTEAx3NdLgApjkRRbA9mrgRgUdrdBJsKC5x6Qo4yksBbIbkLiwxW+BwoKIUnUAdmNSHwAe44dOkRcP14AAAAASUVORK5CYII=";
+
+    BrowsingContext browsingContext = new BrowsingContext(driver, driver.getWindowHandle());
+
+    driver.get(appServer.whereIs("coordinates_tests/simple_page.html"));
+    WebElement element = driver.findElement(By.id("box"));
+
+    Rectangle elementRectangle = element.getRect();
+
+    String screenshot = browsingContext.captureBoxScreenshot(
+      elementRectangle.getX(),
+      elementRectangle.getY(),
+      5,
+      5);
+
+    assertThat(screenshot.length()).isPositive();
+    assertThat(screenshot).isEqualTo(expectedBase64EncodedImage);
+  }
+
   private String alertPage() {
     return appServer.create(
         new Page()