Use a ResizeObserver to determine default font-size for text tracks

third_party/WebKit/Source/core/layout/LayoutTextTrackContainer.cpp

-/*
- * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
- * Copyright (C) 2012 Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "core/layout/LayoutTextTrackContainer.h"
-
-#include "core/frame/DeprecatedScheduleStyleRecalcDuringLayout.h"
-#include "core/layout/LayoutVideo.h"
-
-namespace blink {
-
-LayoutTextTrackContainer::LayoutTextTrackContainer(Element* element)
-    : LayoutBlockFlow(element), font_size_(0) {}
-
-void LayoutTextTrackContainer::GetLayout() {
-  LayoutBlockFlow::GetLayout();
-  if (Style()->Display() == EDisplay::kNone)
-    return;
-
-  DeprecatedScheduleStyleRecalcDuringLayout marker(
-      GetNode()->GetDocument().Lifecycle());
-
-  LayoutObject* media_layout_object = Parent();
-  if (!media_layout_object || !media_layout_object->IsVideo())
-    return;
-  if (UpdateSizes(ToLayoutVideo(*media_layout_object)))
-    ToElement(GetNode())->SetInlineStyleProperty(
-        CSSPropertyFontSize, font_size_, CSSPrimitiveValue::UnitType::kPixels);
-}
-
-bool LayoutTextTrackContainer::UpdateSizes(
-    const LayoutVideo& video_layout_object) {
-  // FIXME: The video size is used to calculate the font size (a workaround
-  // for lack of per-spec vh/vw support) but the whole media element is used
-  // for cue rendering. This is inconsistent. See also the somewhat related
-  // spec bug: https://www.w3.org/Bugs/Public/show_bug.cgi?id=28105
-  LayoutSize video_size = video_layout_object.ReplacedContentRect().size();
-
-  float smallest_dimension =
-      std::min(video_size.Height().ToFloat(), video_size.Width().ToFloat());
-
-  float font_size = smallest_dimension * 0.05f;
-
-  // Avoid excessive FP precision issue.
-  // C11 5.2.4.2.2:9 requires assignment and cast to remove extra precision, but
-  // the behavior is currently not portable. fontSize may have precision higher
-  // than m_fontSize thus straight comparison can fail despite they cast to the
-  // same float value.
-  volatile float& current_font_size = font_size_;
-  float old_font_size = current_font_size;
-  current_font_size = font_size;
-  return current_font_size != old_font_size;
-}
-
-}  // namespace blink