Updating screenshot code to retain scroll bars in required directions.

When an IE window needs to be resized to obtain the full-DOM screenshot,
if it has scroll bars in either direction, those scroll bars need to be
present in the resized window, so that layout recalculation doesn't occur.
In practice, this means reducing the window size by 2 pixels in the
appropriate direction before taking the screenshot. The resulting scroll
bars are cropped from the image.

Author: jimevans

cpp/iedriver/CommandHandlers/ScreenshotCommandHandler.h

@@ -156,25 +156,25 @@ class ScreenshotCommandHandler : public IECommandHandler {
     // If the window is already wide enough to accomodate
     // the document, don't resize that dimension. Otherwise,
     // the window will display a horizontal scroll bar, and
-    // we need to take the scroll bar height into account when
-    // we size resulting image.
-    int horizontal_scrollbar_height = 0;
+    // we need to retain the scrollbar to avoid rerendering
+    // during the resize, so reduce the target window width
+    // by two pixels.
     if (original_width > target_window_width) {
       target_window_width = original_width;
     } else {
-      horizontal_scrollbar_height = ::GetSystemMetrics(SM_CYHSCROLL);
+      target_window_width -= 2;
     }
 
     // If the window is already tall enough to accomodate
     // the document, don't resize that dimension. Otherwise,
     // the window will display a vertical scroll bar, and
-    // we need to take the scrollbar width into account when
-    // we size the resulting image.
-    int vertical_scrollbar_width = 0;
+    // we need to retain the scrollbar to avoid rerendering
+    // during the resize, so reduce the target window height
+    // by two pixels.
     if (original_height > target_window_height) {
       target_window_height = original_height;
     } else {
-      vertical_scrollbar_width = ::GetSystemMetrics(SM_CXVSCROLL);
+      target_window_height -= 2;
     }
 
     BOOL is_maximized = ::IsZoomed(ie_window_handle);
@@ -211,10 +211,12 @@ class ScreenshotCommandHandler : public IECommandHandler {
     }
 
     // Capture the window's canvas to a DIB.
-    BOOL created = this->image_->Create(
-        document_info.width + vertical_scrollbar_width,
-        document_info.height + horizontal_scrollbar_height,
-        /*numbers of bits per pixel = */ 32);
+    // If there are any scroll bars in the window, they should
+    // be explicitly cropped out of the image, because of the
+    // size of image we are creating..
+    BOOL created = this->image_->Create(document_info.width,
+                                        document_info.height,
+                                        /*numbers of bits per pixel = */ 32);
     if (!created) {
       LOG(WARN) << "Unable to initialize image object";
     }

cpp/iedriverserver/CHANGELOG

@@ -9,6 +9,16 @@ available via the project downloads page. Changes in "revision" field indicate
 private releases checked into the prebuilts directory of the source tree, but
 not made generally available on the downloads page.
 
+v2.47.0.5
+=========
+ * Updating screenshot code to retain scroll bars in required directions.
+   When an IE window needs to be resized to obtain the full-DOM screenshot,
+   if it has scroll bars in either direction, those scroll bars need to be
+   present in the resized window, so that layout recalculation doesn't occur.
+   In practice, this means reducing the window size by 2 pixels in the
+   appropriate direction before taking the screenshot. The resulting scroll
+   bars are cropped from the image.
+
 v2.47.0.4
 =========
  * Updates to JavaScript automation atoms.