Intersect presentation area with the scrollable area

When determining the presentation area for delegated ink trails, its
possible that the canvas that the user has provided is larger than the
viewport of the browser window. In this case, the presentation area
should intersect with the scrollable area so that it can extend to the
scroll bars, but not beyond them. This change also ensures that the
presentation area is clipped to the edge of iframes as well.

Bug: 1052145
Change-Id: I349616b25a0523e825dffb37c19e14fe737dc3f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2341949Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Libby <dlibby@microsoft.com>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806824}

third_party/blink/renderer/modules/delegated_ink/delegated_ink_trail_presenter.cc

@@ -10,7 +10,9 @@
 #include "third_party/blink/renderer/core/dom/element.h"
 #include "third_party/blink/renderer/core/events/pointer_event.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
+#include "third_party/blink/renderer/core/frame/visual_viewport.h"
 #include "third_party/blink/renderer/core/geometry/dom_rect.h"
+#include "third_party/blink/renderer/core/layout/layout_embedded_content.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
 #include "third_party/blink/renderer/core/page/chrome_client.h"
 #include "third_party/blink/renderer/core/page/page.h"
@@ -97,14 +99,39 @@ void DelegatedInkTrailPresenter::updateInkTrailStartPoint(
     layout_box = layout_view;
   }
 
-  // TODO(1052145): Move this further into the document lifecycle when layout
-  // is up to date.
-  PhysicalRect physical_rect_area = layout_box->LocalToAbsoluteRect(
+  // Intersect with the visible viewport so that the presentation area can't
+  // extend beyond the edges of the window or over the scrollbars. The frame
+  // visual viewport loop accounts for all iframe viewports, and the page visual
+  // viewport accounts for the full window. Convert everything to root frame
+  // coordinates in order to make sure offsets aren't lost along the way.
+  //
+  // TODO(1052145): Overflow and clip-path clips are ignored here, which results
+  // in delegated ink trails ignoring the clips and appearing incorrectly in
+  // some situations. This could also occur due to transformations, as the
+  // |presenation_area| is currently always a rectilinear bounding box. Ideally
+  // both of these situations are handled correctly, or the trail doesn't appear
+  // if we are unable to accurately render it.
+  PhysicalRect border_box_rect_absolute = layout_box->LocalToAbsoluteRect(
       layout_box->PhysicalBorderBoxRect(), kTraverseDocumentBoundaries);
-  gfx::RectF area(physical_rect_area.X().ToFloat(),
-                  physical_rect_area.Y().ToFloat(),
-                  physical_rect_area.Width().ToFloat(),
-                  physical_rect_area.Height().ToFloat());
+
+  while (layout_view->GetFrame()->OwnerLayoutObject()) {
+    PhysicalRect frame_visual_viewport_absolute =
+        layout_view->LocalToAbsoluteRect(
+            PhysicalRect(
+                layout_view->GetScrollableArea()->VisibleContentRect()),
+            kTraverseDocumentBoundaries);
+    border_box_rect_absolute.Intersect(frame_visual_viewport_absolute);
+
+    layout_view = layout_view->GetFrame()->OwnerLayoutObject()->View();
+  }
+
+  border_box_rect_absolute.Intersect(PhysicalRect(
+      local_frame_->GetPage()->GetVisualViewport().VisibleContentRect()));
+
+  gfx::RectF area(border_box_rect_absolute.X().ToFloat(),
+                  border_box_rect_absolute.Y().ToFloat(),
+                  border_box_rect_absolute.Width().ToFloat(),
+                  border_box_rect_absolute.Height().ToFloat());
 
   const double diameter_in_physical_pixels = style->diameter() * effective_zoom;
   std::unique_ptr<viz::DelegatedInkMetadata> metadata =