Bug 1769640 - P1: Cache content AUPDP in DocAccessibleParents. r=morgan,emilio

This change allows us to remove the `FullZoom` multiplier and fixes text
bounds caclulations in a zoomed page.

Testing: The current browser scroll/bounds tests pass (with the
exception of fission iframes which were already broken).

Differential Revision: https://phabricator.services.mozilla.com/D146507

accessible/base/nsAccessibilityService.cpp

@@ -396,7 +396,7 @@ void nsAccessibilityService::NotifyOfResolutionChange(
   if (StaticPrefs::accessibility_cache_enabled_AtStartup()) {
     DocAccessible* document = GetDocAccessible(aPresShell);
     if (document && document->IPCDoc()) {
-      nsTArray<mozilla::a11y::CacheData> data(1);
+      AutoTArray<mozilla::a11y::CacheData, 1> data;
       RefPtr<AccAttributes> fields = new AccAttributes();
       fields->SetAttribute(nsGkAtoms::resolution, aResolution);
       data.AppendElement(mozilla::a11y::CacheData(0, fields));
@@ -405,6 +405,21 @@ void nsAccessibilityService::NotifyOfResolutionChange(
   }
 }
 
+void nsAccessibilityService::NotifyOfDevPixelRatioChange(
+    mozilla::PresShell* aPresShell, int32_t aAppUnitsPerDevPixel) {
+  if (StaticPrefs::accessibility_cache_enabled_AtStartup()) {
+    DocAccessible* document = GetDocAccessible(aPresShell);
+    if (document && document->IPCDoc()) {
+      AutoTArray<mozilla::a11y::CacheData, 1> data;
+      RefPtr<AccAttributes> fields = new AccAttributes();
+      fields->SetAttribute(nsGkAtoms::_moz_device_pixel_ratio,
+                           aAppUnitsPerDevPixel);
+      data.AppendElement(mozilla::a11y::CacheData(0, fields));
+      document->IPCDoc()->SendCache(CacheUpdateType::Update, data, true);
+    }
+  }
+}
+
 LocalAccessible* nsAccessibilityService::GetRootDocumentAccessible(
     PresShell* aPresShell, bool aCanCreate) {
   PresShell* presShell = aPresShell;

accessible/base/nsAccessibilityService.h

@@ -242,6 +242,9 @@ class nsAccessibilityService final : public mozilla::a11y::DocManager,
   void NotifyOfResolutionChange(mozilla::PresShell* aPresShell,
                                 float aResolution);
 
+  void NotifyOfDevPixelRatioChange(mozilla::PresShell* aPresShell,
+                                   int32_t aAppUnitsPerDevPixel);
+
   // nsAccessibiltiyService
 
   /**

accessible/generic/LocalAccessible.cpp

@@ -3500,6 +3500,10 @@ already_AddRefed<AccAttributes> LocalAccessible::BundleFieldsForCache(
         // will ne notified via nsAS::NotifyOfResolutionChange
         float resolution = presShell->GetResolution();
         fields->SetAttribute(nsGkAtoms::resolution, resolution);
+        int32_t appUnitsPerDevPixel =
+            presShell->GetPresContext()->AppUnitsPerDevPixel();
+        fields->SetAttribute(nsGkAtoms::_moz_device_pixel_ratio,
+                             appUnitsPerDevPixel);
       }
     }
   }

accessible/ipc/RemoteAccessibleBase.cpp

@@ -396,28 +396,11 @@ LayoutDeviceIntRect RemoteAccessibleBase<Derived>::BoundsWithOffset(
     Maybe<nsRect> maybeBounds = RetrieveCachedBounds();
     if (maybeBounds) {
       nsRect bounds = *maybeBounds;
-#if !defined(ANDROID)
-      dom::CanonicalBrowsingContext* cbc =
-          static_cast<dom::BrowserParent*>(mDoc->Manager())
-              ->GetBrowsingContext()
-              ->Top();
-      dom::BrowserParent* bp = cbc->GetBrowserParent();
-      nsPresContext* presContext =
-          bp->GetOwnerElement()->OwnerDoc()->GetPresContext();
-      float fullZoom = cbc->GetFullZoom();
-#else
-      // In Android the FullZoom is always 1.0 since we use APZ/resolution zoom.
-      float fullZoom = 1.0;
-#endif
+      const DocAccessibleParent* topDoc = IsDoc() ? AsDoc() : nullptr;
 
       if (aOffset.isSome()) {
         // The rect we've passed in is in app units, so no conversion needed.
         nsRect internalRect = *aOffset;
-        // XXX: Right now this is exclusively used for
-        // text bounds, which already have their zoom level
-        // applied. Remove it, because we'll multiply it back
-        // in later on.
-        internalRect.ScaleRoundOut(1 / fullZoom);
         bounds.SetRectX(bounds.x + internalRect.x, internalRect.width);
         bounds.SetRectY(bounds.y + internalRect.y, internalRect.height);
       }
@@ -450,6 +433,8 @@ LayoutDeviceIntRect RemoteAccessibleBase<Derived>::BoundsWithOffset(
                 nsGkAtoms::resolution);
             MOZ_ASSERT(res, "No cached document resolution found.");
             bounds.ScaleRoundOut(res.valueOr(1.0f));
+
+            topDoc = remoteAcc->AsDoc();
           }
 
           // Apply scroll offset, if applicable. Only the contents of an
@@ -468,24 +453,31 @@ LayoutDeviceIntRect RemoteAccessibleBase<Derived>::BoundsWithOffset(
         acc = acc->Parent();
       }
 
+      MOZ_ASSERT(topDoc);
+      if (topDoc) {
+        // We use the top documents app-unites-per-dev-pixel even though
+        // theoretically nested docs can have different values. Practically,
+        // that isn't likely since we only offer zoom controls for the top
+        // document and all subdocuments inherit from it.
+        auto appUnitsPerDevPixel = topDoc->mCachedFields->GetAttribute<int32_t>(
+            nsGkAtoms::_moz_device_pixel_ratio);
+        MOZ_ASSERT(appUnitsPerDevPixel);
+        if (appUnitsPerDevPixel) {
+          // Convert our existing `bounds` rect from app units to dev pixels
+          devPxBounds = LayoutDeviceIntRect::FromAppUnitsToNearest(
+              bounds, *appUnitsPerDevPixel);
+        }
+      }
+
 #if !defined(ANDROID)
-      // This block is not thread safe because it queries a LocalAccessible,
-      // the BrowsingContext, PresContext, etc. It is also not needed in
-      // Android since the only local accessible is the outer doc browser that
-      // has an offset of 0 and a FullZoom value of 1.0.
+      // This block is not thread safe because it queries a LocalAccessible.
+      // It is also not needed in Android since the only local accessible is
+      // the outer doc browser that has an offset of 0.
       if (LocalAccessible* localAcc = const_cast<Accessible*>(acc)->AsLocal()) {
         // LocalAccessible::Bounds returns screen-relative bounds in
         // dev pixels.
         LayoutDeviceIntRect localBounds = localAcc->Bounds();
 
-        // Convert our existing `bounds` rect from app units to dev pixels
-        devPxBounds = LayoutDeviceIntRect::FromAppUnitsToNearest(
-            bounds, presContext->AppUnitsPerDevPixel());
-
-        // We factor in our zoom level before offsetting by
-        // `localBounds`, which has already taken zoom into account.
-        devPxBounds.ScaleRoundOut(fullZoom);
-
         // The root document will always have an APZ resolution of 1,
         // so we don't factor in its scale here. We also don't scale
         // by GetFullZoom because LocalAccessible::Bounds already does

layout/base/nsPresContext.cpp

@@ -91,6 +91,9 @@
 #include "mozilla/layers/APZThreadUtils.h"
 #include "MobileViewportManager.h"
 #include "mozilla/dom/ImageTracker.h"
+#ifdef ACCESSIBILITY
+#  include "mozilla/a11y/DocAccessible.h"
+#endif
 
 // Needed for Start/Stop of Image Animation
 #include "imgIContainer.h"
@@ -492,6 +495,15 @@ void nsPresContext::AppUnitsPerDevPixelChanged() {
 
   mCurAppUnitsPerDevPixel = mDeviceContext->AppUnitsPerDevPixel();
 
+#ifdef ACCESSIBILITY
+  if (mCurAppUnitsPerDevPixel != oldAppUnitsPerDevPixel) {
+    if (nsAccessibilityService* accService = GetAccService()) {
+      accService->NotifyOfDevPixelRatioChange(mPresShell,
+                                              mCurAppUnitsPerDevPixel);
+    }
+  }
+#endif
+
   // Recompute the size for vh units since it's changed by the dynamic toolbar
   // max height which is stored in screen coord.
   if (IsRootContentDocumentCrossProcess()) {