From 0e4ceea622008c10cd297338fd29557ad932175b Mon Sep 17 00:00:00 2001 From: Botond Ballo Date: Tue, 5 May 2020 19:24:28 +0000 Subject: [PATCH] Bug 1556556 - Introduce ViewportType and RelativeTo. r=kats,mattwoodrow Differential Revision: https://phabricator.services.mozilla.com/D68916 --- layout/base/nsLayoutUtils.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h index 8c6e2272e02c..f2bfc632c5f7 100644 --- a/layout/base/nsLayoutUtils.h +++ b/layout/base/nsLayoutUtils.h @@ -132,6 +132,39 @@ enum class DrawStringFlags { }; MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(DrawStringFlags) +// A flag that can be used to annotate a frame to distinguish coordinates +// relative to the viewport frame as being in layout or visual coordinates. +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") + << "}"; + } +}; + /** * nsLayoutUtils is a namespace class used for various helper * functions that are useful in multiple places in layout. The goal