Added methods to capture element screenshot after scrolling into view vertically centered (#62)

* added script to allow scrolling element to center of screen

In some instance using scrollIntoView(true) causes the element to be hidden beneath a fixed element such as a fixed nav bar. Using this setup the element can be scrolled  into view so that it is verticlly centered in the screen

* refined method signature to not include unnecessary boolean.

Also updated comments

Author: deepthought42

src/main/java/com/assertthat/selenium_shutterbug/core/Shutterbug.java

@@ -113,6 +113,17 @@ public static PageSnapshot shootPage(WebDriver driver, ScrollStrategy scroll, in
         return pageScreenshot;
     }
 
+    /**
+     * To be used when need to screenshot particular element by vertically centering it in viewport.
+     *
+     * @param driver  WebDriver instance
+     * @param element WebElement instance to be screenshotted
+     * @return ElementSnapshot instance
+     */
+    public static ElementSnapshot shootElementVerticallyCentered(WebDriver driver, WebElement element) {
+        return shootElementVerticallyCentered(driver,element,false);
+    }
+    
     /**
      * To be used when need to screenshot particular element.
      *
@@ -139,4 +150,21 @@ public static ElementSnapshot shootElement(WebDriver driver, WebElement element,
         elementSnapshot.setImage(browser.takeScreenshot(),browser.getBoundingClientRect(element));
         return elementSnapshot;
     }
+    
+    /**
+     * To be used when need to screenshot particular element by vertically centering it within viewport.
+     *
+     * @param driver  WebDriver instance
+     * @param element WebElement instance to be screen shot
+     * @param useDevicePixelRatio whether or not take into account device pixel ratio
+     * 
+     * @return ElementSnapshot instance
+     */
+    public static ElementSnapshot shootElementVerticallyCentered(WebDriver driver, WebElement element, boolean useDevicePixelRatio) {
+        Browser browser = new Browser(driver, useDevicePixelRatio);
+        ElementSnapshot elementSnapshot = new ElementSnapshot(driver, browser.getDevicePixelRatio());
+        browser.scrollToElementVerticalCentered(element);
+        elementSnapshot.setImage(browser.takeScreenshot(),browser.getBoundingClientRect(element));
+        return elementSnapshot;
+    }
 }

src/main/java/com/assertthat/selenium_shutterbug/utils/web/Browser.java

@@ -47,6 +47,7 @@ public class Browser {
     private static final String VIEWPORT_WIDTH_JS = "js/viewport-width.js";
     private static final String SCROLL_TO_JS = "js/scroll-to.js";
     private static final String SCROLL_INTO_VIEW_JS = "js/scroll-element-into-view.js";
+    private static final String SCROLL_INTO_VIEW_VERTICAL_CENTERED_JS = "js/scroll-element-into-view-vertical-centered.js";
     private static final String CURRENT_SCROLL_Y_JS = "js/get-current-scrollY.js";
     private static final String CURRENT_SCROLL_X_JS = "js/get-current-scrollX.js";
     private static final String DEVICE_PIXEL_RATIO = "js/get-device-pixel-ratio.js";
@@ -256,6 +257,10 @@ public void scrollToElement(WebElement element) {
         executeJsScript(SCROLL_INTO_VIEW_JS, element);
     }
 
+    public void scrollToElementVerticalCentered(WebElement element) {
+    	executeJsScript(SCROLL_INTO_VIEW_VERTICAL_CENTERED_JS, element);
+    }
+    
     public void scrollTo(int x, int y) {
         executeJsScript(SCROLL_TO_JS, x / devicePixelRatio, y / devicePixelRatio);
     }

src/main/resources/js/scroll-element-into-view-vertical-centered.js

@@ -0,0 +1 @@
+arguments[0].scrollIntoView({block: 'center'});