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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_RelativeTo_h
#define mozilla_RelativeTo_h
#include <ostream>
class nsIFrame;
namespace mozilla {
// A flag that can be used to distinguish between the visual and layout
// viewports. In layout code, this is often used to annotate coordinates
// relative to the viewport frame as being in layout or visual coordinates.
// However, it may also be used to e.g. specify whether a scroll operation
// should apply to the layout or visual viewport.
enum class ViewportType { Layout, Visual };
// A struct that combines a frame with a ViewportType annotation. The
// combination completely describes what a set of coordinates is "relative to".
// Notes on expected usage:
// - The boundary between visual and layout coordinates is approximately
// at the root content document (RCD)'s ViewportFrame, which we'll
// call "RCD-VF".
// - Coordinates relative to the RCD-VF's descendants (other than the
// RCD's viewport scrollbar frames) should be in layout coordinates.
// - Coordinates relative to the RCD-VF's ancestors should be in visual
// coordinates (note that in an e10s setup, the RCD-VF doesn't
// typically have in-process ancestors).
// - Coordinates relative to the RCD-VF itself can be in either layout
// or visual coordinates.
struct RelativeTo {
const nsIFrame* mFrame = nullptr;
// Choose ViewportType::Layout as the default as this is what the vast
// majority of layout code deals with.
ViewportType mViewportType = ViewportType::Layout;
bool operator==(const RelativeTo& aOther) const {
return mFrame == aOther.mFrame && mViewportType == aOther.mViewportType;
}
friend std::ostream& operator<<(std::ostream& aOs, const RelativeTo& aR) {
return aOs << "{" << aR.mFrame << ", "
<< (aR.mViewportType == ViewportType::Visual ? "visual"
: "layout")
<< "}";
}
};
} // namespace mozilla
#endif // mozilla_RelativeTo_h
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