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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 */
#ifndef MobileViewportManager_h_
#define MobileViewportManager_h_
#include "mozilla/Maybe.h"
#include "mozilla/MVMContext.h"
#include "nsCOMPtr.h"
#include "nsIDOMEventListener.h"
#include "nsIObserver.h"
#include "Units.h"
class nsViewportInfo;
namespace mozilla {
class MVMContext;
namespace dom {
class Document;
class EventTarget;
} // namespace dom
} // namespace mozilla
class MobileViewportManager final : public nsIDOMEventListener,
public nsIObserver {
/* The MobileViewportManager might be required to handle meta-viewport tags
* and changes, or it might not (e.g. if we are in a desktop-zooming setup).
* This enum indicates which mode the manager is in. It might make sense to
* split these two "modes" into two separate classes but for now they have a
* bunch of shared code and it's uncertain if that shared set will expand or
* contract. */
enum class ManagerType { VisualAndMetaViewport, VisualViewportOnly };
explicit MobileViewportManager(mozilla::MVMContext* aContext,
ManagerType aType);
void Destroy();
ManagerType GetManagerType() { return mManagerType; }
/* Provide a resolution to use during the first paint instead of the default
* resolution computed from the viewport info metadata. This is in the same
* "units" as the argument to nsDOMWindowUtils::SetResolutionAndScaleTo.
* Also takes the previous display dimensions as they were at the time the
* resolution was stored in order to correctly adjust the resolution if the
* device was rotated in the meantime. */
void SetRestoreResolution(float aResolution,
mozilla::LayoutDeviceIntSize aDisplaySize);
/* Compute the "intrinsic resolution", which is the smallest resolution at
* which the layout viewport fills the visual viewport. (In typical
* scenarios, where the aspect ratios of the two viewports match, it's the
* resolution at which they are the same size.)
* The returned resolution is suitable for passing to
* PresShell::SetResolutionAndScaleTo(). It's not in typed units for
* reasons explained at the declaration of FrameMetrics::mPresShellResolution.
float ComputeIntrinsicResolution() const;
/* The only direct calls to this should be in test code.
* Normally, it gets called by HandleEvent().
void HandleDOMMetaAdded();
void SetRestoreResolution(float aResolution);
/* Notify the MobileViewportManager that a reflow is about to happen. This
* triggers the MVM to update its internal notion of display size and CSS
* viewport, so that code that queries those during the reflow gets an
* up-to-date value.
void UpdateSizesBeforeReflow();
/* Notify the MobileViewportManager that a reflow was requested in the
* presShell.*/
void RequestReflow(bool aForceAdjustResolution);
/* Notify the MobileViewportManager that the resolution on the presShell was
* updated, and the visual viewport size needs to be updated. */
void ResolutionUpdated(mozilla::ResolutionChangeOrigin aOrigin);
/* Called to compute the initial viewport on page load or before-first-paint,
* whichever happens first. Also called directly if we are created after the
* presShell is initialized. */
void SetInitialViewport();
const mozilla::LayoutDeviceIntSize& DisplaySize() const {
return mDisplaySize;
* Shrink the content to fit it to the display width if no initial-scale is
* specified and if the content is still wider than the display width.
void ShrinkToDisplaySizeIfNeeded();
* Similar to UpdateVisualViewportSize but this should be called only when we
* need to update visual viewport size in response to dynamic toolbar
* transitions.
* This function doesn't cause any reflows, just fires a visual viewport
* resize event.
void UpdateVisualViewportSizeByDynamicToolbar(
mozilla::ScreenIntCoord aToolbarHeight);
nsSize GetVisualViewportSizeUpdatedByDynamicToolbar() const {
return mVisualViewportSizeUpdatedByDynamicToolbar;
* This refreshes the visual viewport size based on the most recently
* available information. It is intended to be called in particular after
* the root scrollframe does a reflow, which may make scrollbars appear or
* disappear if the content changed size.
void UpdateVisualViewportSizeForPotentialScrollbarChange();
* Returns the composition size in CSS units when zoomed to the intrinsic
* scale.
mozilla::CSSSize GetIntrinsicCompositionSize() const;
/* Main helper method to update the CSS viewport and any other properties that
* need updating. */
void RefreshViewportSize(bool aForceAdjustResolution);
/* Secondary main helper method to update just the visual viewport size. */
void RefreshVisualViewportSize();
/* Helper to clamp the given zoom by the min/max in the viewport info. */
mozilla::CSSToScreenScale ClampZoom(
const mozilla::CSSToScreenScale& aZoom,
const nsViewportInfo& aViewportInfo) const;
/* Helper to update the given zoom according to changed display and viewport
* widths. */
mozilla::CSSToScreenScale ScaleZoomWithDisplayWidth(
const mozilla::CSSToScreenScale& aZoom,
const float& aDisplayWidthChangeRatio,
const mozilla::CSSSize& aNewViewport,
const mozilla::CSSSize& aOldViewport);
mozilla::CSSToScreenScale ResolutionToZoom(
const mozilla::LayoutDeviceToLayerScale& aResolution) const;
mozilla::LayoutDeviceToLayerScale ZoomToResolution(
const mozilla::CSSToScreenScale& aZoom) const;
/* Updates the presShell resolution and the visual viewport size for various
* types of changes. */
void UpdateResolutionForFirstPaint(const mozilla::CSSSize& aViewportSize);
void UpdateResolutionForViewportSizeChange(
const mozilla::CSSSize& aViewportSize,
const mozilla::Maybe<float>& aDisplayWidthChangeRatio);
void UpdateResolutionForContentSizeChange(
const mozilla::CSSSize& aContentSize);
void ApplyNewZoom(const mozilla::ScreenIntSize& aDisplaySize,
const mozilla::CSSToScreenScale& aNewZoom);
void UpdateVisualViewportSize(const mozilla::ScreenIntSize& aDisplaySize,
const mozilla::CSSToScreenScale& aZoom);
/* Updates the displayport margins for the presShell's root scrollable frame
void UpdateDisplayPortMargins();
/* Helper function for ComputeIntrinsicResolution(). */
mozilla::CSSToScreenScale ComputeIntrinsicScale(
const nsViewportInfo& aViewportInfo,
const mozilla::ScreenIntSize& aDisplaySize,
const mozilla::CSSSize& aViewportOrContentSize) const;
* Returns the screen size subtracted the scrollbar sizes from |aDisplaySize|.
mozilla::ScreenIntSize GetCompositionSize(
const mozilla::ScreenIntSize& aDisplaySize) const;
mozilla::CSSToScreenScale GetZoom() const;
RefPtr<mozilla::MVMContext> mContext;
ManagerType mManagerType;
bool mIsFirstPaint;
bool mPainted;
mozilla::LayoutDeviceIntSize mDisplaySize;
mozilla::CSSSize mMobileViewportSize;
mozilla::Maybe<float> mRestoreResolution;
mozilla::Maybe<mozilla::ScreenIntSize> mRestoreDisplaySize;
* The visual viewport size updated by the dynamic toolbar transitions. This
* is typically used for the VisualViewport width/height APIs.
* NOTE: If you want to use this value, you should make sure to flush
* position:fixed elements layout and update
* FrameMetrics.mFixedLayerMargins to conform with this value.
nsSize mVisualViewportSizeUpdatedByDynamicToolbar;