gecko-dev/layout/base/MobileViewportManager.cpp
Kartikaya Gupta ed365c4387 Bug 1178847 - Add a MobileViewportManager to manage setting the CSS viewport on B2G. r=botond,tn
The MobileViewportManager ("MVM") is responsible for setting the CSS viewport on
any of the following events:
- a page is painted for the first time (on the before-first-paint event)
- a meta-viewport tag is added (on the DOMMetaAdded event)
- the full-zoom is changed (on the FullZoomChanged event)
- if the window is resized (ResizeReflow gets called as part of normal layout
  processing, and this will pick up a new CSS viewport from MVM)

If the CSS viewport changes or if it is the initial paint, the MVM additionally
calls SetResolutionAndScaleTo on the presShell to update the displayed zoom.
The APZ code in AsyncPanZoomController::NotifyLayersUpdated already has
corresponding code to accept this updated zoom when the CSS viewport changes.
2015-07-21 10:51:55 -04:00

282 lines
11 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */
#include "MobileViewportManager.h"
#include "LayersLogging.h"
#include "nsViewManager.h"
#include "nsViewportInfo.h"
#define MVM_LOG(...)
// #define MVM_LOG(...) printf_stderr("MVM: " __VA_ARGS__)
NS_IMPL_ISUPPORTS(MobileViewportManager, nsIDOMEventListener, nsIObserver)
static const nsLiteralString DOM_META_ADDED = NS_LITERAL_STRING("DOMMetaAdded");
static const nsLiteralString FULL_ZOOM_CHANGE = NS_LITERAL_STRING("FullZoomChange");
static const nsLiteralCString BEFORE_FIRST_PAINT = NS_LITERAL_CSTRING("before-first-paint");
using namespace mozilla;
using namespace mozilla::layers;
MobileViewportManager::MobileViewportManager(nsIPresShell* aPresShell,
nsIDocument* aDocument)
: mDocument(aDocument)
, mPresShell(aPresShell)
, mIsFirstPaint(false)
{
MOZ_ASSERT(mPresShell);
MOZ_ASSERT(mDocument);
MVM_LOG("%p: creating with presShell %p document %p\n", this, mPresShell, aDocument);
if (nsCOMPtr<nsPIDOMWindow> window = mDocument->GetWindow()) {
mEventTarget = window->GetChromeEventHandler();
}
if (mEventTarget) {
mEventTarget->AddEventListener(DOM_META_ADDED, this, false);
mEventTarget->AddEventListener(FULL_ZOOM_CHANGE, this, false);
}
nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
if (observerService) {
observerService->AddObserver(this, BEFORE_FIRST_PAINT.Data(), false);
}
}
MobileViewportManager::~MobileViewportManager()
{
}
void
MobileViewportManager::Destroy()
{
MVM_LOG("%p: destroying\n", this);
if (mEventTarget) {
mEventTarget->RemoveEventListener(DOM_META_ADDED, this, false);
mEventTarget->RemoveEventListener(FULL_ZOOM_CHANGE, this, false);
mEventTarget = nullptr;
}
nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
if (observerService) {
observerService->RemoveObserver(this, BEFORE_FIRST_PAINT.Data());
}
mDocument = nullptr;
mPresShell = nullptr;
}
void
MobileViewportManager::RequestReflow()
{
MVM_LOG("%p: got a reflow request\n", this);
RefreshViewportSize(false);
}
NS_IMETHODIMP
MobileViewportManager::HandleEvent(nsIDOMEvent* event)
{
nsAutoString type;
event->GetType(type);
if (type.Equals(DOM_META_ADDED)) {
MVM_LOG("%p: got a dom-meta-added event\n", this);
RefreshViewportSize(true);
} else if (type.Equals(FULL_ZOOM_CHANGE)) {
MVM_LOG("%p: got a full-zoom-change event\n", this);
RefreshViewportSize(false);
}
return NS_OK;
}
NS_IMETHODIMP
MobileViewportManager::Observe(nsISupports* aSubject, const char* aTopic, const char16_t* aData)
{
if (SameCOMIdentity(aSubject, mDocument) && BEFORE_FIRST_PAINT.EqualsASCII(aTopic)) {
MVM_LOG("%p: got a before-first-paint event\n", this);
mIsFirstPaint = true;
RefreshViewportSize(false);
}
return NS_OK;
}
CSSToScreenScale
MobileViewportManager::UpdateResolution(const nsViewportInfo& aViewportInfo,
const ScreenIntSize& aDisplaySize,
const CSSSize& aViewport,
const Maybe<float>& aDisplayWidthChangeRatio)
{
CSSToLayoutDeviceScale cssToDev((float)nsPresContext::AppUnitsPerCSSPixel()
/ mPresShell->GetPresContext()->AppUnitsPerDevPixel());
LayoutDeviceToLayerScale res(nsLayoutUtils::GetResolution(mPresShell));
#if defined(MOZ_WIDGET_GONK) || defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
if (mIsFirstPaint) {
CSSToScreenScale defaultZoom = aViewportInfo.GetDefaultZoom();
MVM_LOG("%p: default zoom from viewport is %f\n", this, defaultZoom.scale);
// FIXME/bug 799585(?): GetViewportInfo() returns a default zoom of
// 0.0 to mean "did not calculate a zoom". In that case, we default
// it to the intrinsic scale.
if (defaultZoom.scale < 0.01f) {
defaultZoom = MaxScaleRatio(ScreenSize(aDisplaySize), aViewport);
MVM_LOG("%p: Intrinsic computed zoom is %f\n", this, defaultZoom.scale);
}
MOZ_ASSERT(aViewportInfo.GetMinZoom() <= defaultZoom &&
defaultZoom <= aViewportInfo.GetMaxZoom());
CSSToParentLayerScale zoom = ViewTargetAs<ParentLayerPixel>(defaultZoom,
PixelCastJustification::ScreenIsParentLayerForRoot);
LayoutDeviceToLayerScale resolution = zoom / cssToDev * ParentLayerToLayerScale(1);
MVM_LOG("%p: setting resolution %f\n", this, resolution.scale);
nsLayoutUtils::SetResolutionAndScaleTo(mPresShell, resolution.scale);
return defaultZoom;
}
// If this is not a first paint, then in some cases we want to update the pre-
// existing resolution so as to maintain how much actual content is visible
// within the display width. Note that "actual content" may be different with
// respect to CSS pixels because of the CSS viewport size changing.
//
// aDisplayWidthChangeRatio is non-empty if:
// (a) The meta-viewport tag information changes, and so the CSS viewport
// might change as a result. In this case, we want to adjust the zoom to
// compensate. OR
// (b) The display size changed from a nonzero value to another nonzero value.
// This covers the case where e.g. the device was rotated, and again we
// want to adjust the zoom to compensate.
// Note in particular that aDisplayWidthChangeRatio will be None if all that
// happened was a change in the full-zoom. In this case, we still want to
// compute a new CSS viewport, but we don't want to update the resolution.
//
// Given the above, the algorithm below accounts for all types of changes I
// can conceive of:
// 1. screen size changes, CSS viewport does not (pages with no meta viewport
// or a fixed size viewport)
// 2. screen size changes, CSS viewport also does (pages with a device-width
// viewport)
// 3. screen size remains constant, but CSS viewport changes (meta viewport
// tag is added or removed)
// 4. neither screen size nor CSS viewport changes
if (aDisplayWidthChangeRatio) {
float cssViewportChangeRatio = (mMobileViewportSize.width == 0)
? 1.0f : aViewport.width / mMobileViewportSize.width;
LayoutDeviceToLayerScale newRes(res.scale * aDisplayWidthChangeRatio.value()
/ cssViewportChangeRatio);
MVM_LOG("%p: Old resolution was %f, changed by %f/%f to %f\n", this, res.scale,
aDisplayWidthChangeRatio.value(), cssViewportChangeRatio, newRes.scale);
nsLayoutUtils::SetResolutionAndScaleTo(mPresShell, newRes.scale);
res = newRes;
}
#endif
return ViewTargetAs<ScreenPixel>(cssToDev * res / ParentLayerToLayerScale(1),
PixelCastJustification::ScreenIsParentLayerForRoot);
}
void
MobileViewportManager::UpdateSPCSPS(const ScreenIntSize& aDisplaySize,
const CSSToScreenScale& aZoom)
{
ScreenSize compositionSize(aDisplaySize);
ScreenMargin scrollbars =
CSSMargin::FromAppUnits(
nsLayoutUtils::ScrollbarAreaToExcludeFromCompositionBoundsFor(
mPresShell->GetRootScrollFrame()))
* CSSToScreenScale(1.0f); // Scrollbars are not subject to scaling, so
// CSS pixels = layer pixels for them (modulo bug 1168487).
compositionSize.width -= scrollbars.LeftRight();
compositionSize.height -= scrollbars.TopBottom();
CSSSize compSize = compositionSize / aZoom;
MVM_LOG("%p: Setting SPCSPS %s\n", this, Stringify(compSize).c_str());
nsLayoutUtils::SetScrollPositionClampingScrollPortSize(mPresShell, compSize);
}
void
MobileViewportManager::UpdateDisplayPortMargins()
{
if (nsIScrollableFrame* root = mPresShell->GetRootScrollFrameAsScrollable()) {
nsLayoutUtils::CalculateAndSetDisplayPortMargins(root,
nsLayoutUtils::RepaintMode::DoNotRepaint);
}
}
void
MobileViewportManager::RefreshViewportSize(bool aForceAdjustResolution)
{
// This function gets called by the various triggers that may result in a
// change of the CSS viewport. In some of these cases (e.g. the meta-viewport
// tag changes) we want to update the resolution and in others (e.g. the full
// zoom changing) we don't want to update the resolution. See the comment in
// UpdateResolution for some more detail on this. An important assumption we
// make here is that this RefreshViewportSize function will be called
// separately for each trigger that changes. For instance it should never get
// called such that both the full zoom and the meta-viewport tag have changed;
// instead it would get called twice - once after each trigger changes. This
// assumption is what allows the aForceAdjustResolution parameter to work as
// intended; if this assumption is violated then we will need to add extra
// complicated logic in UpdateResolution to ensure we only do the resolution
// update in the right scenarios.
Maybe<float> displayWidthChangeRatio;
LayoutDeviceIntSize newDisplaySize;
if (nsLayoutUtils::GetContentViewerSize(mPresShell->GetPresContext(), newDisplaySize)) {
// See the comment in UpdateResolution for why we're doing this.
if (mDisplaySize.width > 0) {
if (aForceAdjustResolution || mDisplaySize.width != newDisplaySize.width) {
displayWidthChangeRatio = Some((float)newDisplaySize.width / (float)mDisplaySize.width);
}
} else if (aForceAdjustResolution) {
displayWidthChangeRatio = Some(1.0f);
}
MVM_LOG("%p: Display width change ratio is %f\n", this, displayWidthChangeRatio.valueOr(0.0f));
mDisplaySize = newDisplaySize;
}
MVM_LOG("%p: Computing CSS viewport using %d,%d\n", this,
mDisplaySize.width, mDisplaySize.height);
if (mDisplaySize.width == 0 || mDisplaySize.height == 0) {
// We can't do anything useful here, we should just bail out
return;
}
ScreenIntSize displaySize = ViewAs<ScreenPixel>(
mDisplaySize, PixelCastJustification::LayoutDeviceIsScreenForBounds);
nsViewportInfo viewportInfo = nsContentUtils::GetViewportInfo(
mDocument, displaySize);
CSSSize viewport = viewportInfo.GetSize();
MVM_LOG("%p: Computed CSS viewport %s\n", this, Stringify(viewport).c_str());
if (!mIsFirstPaint && mMobileViewportSize == viewport) {
// Nothing changed, so no need to do a reflow
return;
}
// If it's the first-paint or the viewport changed, we need to update
// various APZ properties (the zoom and some things that might depend on it)
MVM_LOG("%p: Updating properties because %d || %d\n", this,
mIsFirstPaint, mMobileViewportSize != viewport);
CSSToScreenScale zoom = UpdateResolution(viewportInfo, displaySize, viewport,
displayWidthChangeRatio);
MVM_LOG("%p: New zoom is %f\n", this, zoom.scale);
UpdateSPCSPS(displaySize, zoom);
UpdateDisplayPortMargins();
// Update internal state.
mIsFirstPaint = false;
mMobileViewportSize = viewport;
// Kick off a reflow.
mPresShell->ResizeReflowIgnoreOverride(
nsPresContext::CSSPixelsToAppUnits(viewport.width),
nsPresContext::CSSPixelsToAppUnits(viewport.height));
}