1 files changed, 373 insertions, 0 deletions
diff --git a/layout/generic/nsFontInflationData.cpp b/layout/generic/nsFontInflationData.cpp
new file mode 100644
index 0000000000..943b4109ad
--- /dev/null
+++ b/layout/generic/nsFontInflationData.cpp
@@ -0,0 +1,373 @@
+/* -*- 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/. */
+
+/* Per-block-formatting-context manager of font size inflation for pan and zoom
+ * UI. */
+
+#include "nsFontInflationData.h"
+#include "FrameProperties.h"
+#include "nsTextControlFrame.h"
+#include "nsListControlFrame.h"
+#include "nsComboboxControlFrame.h"
+#include "mozilla/dom/Text.h"  // for inline nsINode::AsText() definition
+#include "mozilla/PresShell.h"
+#include "mozilla/ReflowInput.h"
+#include "nsTextFrameUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::layout;
+
+NS_DECLARE_FRAME_PROPERTY_DELETABLE(FontInflationDataProperty,
+                                    nsFontInflationData)
+
+/* static */ nsFontInflationData* nsFontInflationData::FindFontInflationDataFor(
+    const nsIFrame* aFrame) {
+  // We have one set of font inflation data per block formatting context.
+  const nsIFrame* bfc = FlowRootFor(aFrame);
+  NS_ASSERTION(bfc->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT),
+               "should have found a flow root");
+  MOZ_ASSERT(aFrame->GetWritingMode().IsVertical() ==
+                 bfc->GetWritingMode().IsVertical(),
+             "current writing mode should match that of our flow root");
+
+  return bfc->GetProperty(FontInflationDataProperty());
+}
+
+/* static */
+bool nsFontInflationData::UpdateFontInflationDataISizeFor(
+    const ReflowInput& aReflowInput) {
+  nsIFrame* bfc = aReflowInput.mFrame;
+  NS_ASSERTION(bfc->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT),
+               "should have been given a flow root");
+  nsFontInflationData* data = bfc->GetProperty(FontInflationDataProperty());
+  bool oldInflationEnabled;
+  nscoord oldUsableISize;
+  if (data) {
+    oldUsableISize = data->mUsableISize;
+    oldInflationEnabled = data->mInflationEnabled;
+  } else {
+    data = new nsFontInflationData(bfc);
+    bfc->SetProperty(FontInflationDataProperty(), data);
+    oldUsableISize = -1;
+    oldInflationEnabled = true; /* not relevant */
+  }
+
+  data->UpdateISize(aReflowInput);
+
+  if (oldInflationEnabled != data->mInflationEnabled) return true;
+
+  return oldInflationEnabled && oldUsableISize != data->mUsableISize;
+}
+
+/* static */
+void nsFontInflationData::MarkFontInflationDataTextDirty(nsIFrame* aBFCFrame) {
+  NS_ASSERTION(aBFCFrame->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT),
+               "should have been given a flow root");
+
+  nsFontInflationData* data =
+      aBFCFrame->GetProperty(FontInflationDataProperty());
+  if (data) {
+    data->MarkTextDirty();
+  }
+}
+
+nsFontInflationData::nsFontInflationData(nsIFrame* aBFCFrame)
+    : mBFCFrame(aBFCFrame),
+      mUsableISize(0),
+      mTextAmount(0),
+      mTextThreshold(0),
+      mInflationEnabled(false),
+      mTextDirty(true) {}
+
+/**
+ * Find the closest common ancestor between aFrame1 and aFrame2, except
+ * treating the parent of a frame as the first-in-flow of its parent (so
+ * the result doesn't change when breaking changes).
+ *
+ * aKnownCommonAncestor is a known common ancestor of both.
+ */
+static nsIFrame* NearestCommonAncestorFirstInFlow(
+    nsIFrame* aFrame1, nsIFrame* aFrame2, nsIFrame* aKnownCommonAncestor) {
+  aFrame1 = aFrame1->FirstInFlow();
+  aFrame2 = aFrame2->FirstInFlow();
+  aKnownCommonAncestor = aKnownCommonAncestor->FirstInFlow();
+
+  AutoTArray<nsIFrame*, 32> ancestors1, ancestors2;
+  for (nsIFrame* f = aFrame1; f != aKnownCommonAncestor;
+       (f = f->GetParent()) && (f = f->FirstInFlow())) {
+    ancestors1.AppendElement(f);
+  }
+  for (nsIFrame* f = aFrame2; f != aKnownCommonAncestor;
+       (f = f->GetParent()) && (f = f->FirstInFlow())) {
+    ancestors2.AppendElement(f);
+  }
+
+  nsIFrame* result = aKnownCommonAncestor;
+  uint32_t i1 = ancestors1.Length(), i2 = ancestors2.Length();
+  while (i1-- != 0 && i2-- != 0) {
+    if (ancestors1[i1] != ancestors2[i2]) {
+      break;
+    }
+    result = ancestors1[i1];
+  }
+
+  return result;
+}
+
+static nscoord ComputeDescendantISize(const ReflowInput& aAncestorReflowInput,
+                                      nsIFrame* aDescendantFrame) {
+  nsIFrame* ancestorFrame = aAncestorReflowInput.mFrame->FirstInFlow();
+  if (aDescendantFrame == ancestorFrame) {
+    return aAncestorReflowInput.ComputedISize();
+  }
+
+  AutoTArray<nsIFrame*, 16> frames;
+  for (nsIFrame* f = aDescendantFrame; f != ancestorFrame;
+       f = f->GetParent()->FirstInFlow()) {
+    frames.AppendElement(f);
+  }
+
+  // This ignores the inline-size contributions made by scrollbars, though in
+  // reality we don't have any scrollbars on the sorts of devices on
+  // which we use font inflation, so it's not a problem.  But it may
+  // occasionally cause problems when writing tests on desktop.
+
+  uint32_t len = frames.Length();
+  ReflowInput* reflowInputs =
+      static_cast<ReflowInput*>(moz_xmalloc(sizeof(ReflowInput) * len));
+  nsPresContext* presContext = aDescendantFrame->PresContext();
+  for (uint32_t i = 0; i < len; ++i) {
+    const ReflowInput& parentReflowInput =
+        (i == 0) ? aAncestorReflowInput : reflowInputs[i - 1];
+    nsIFrame* frame = frames[len - i - 1];
+    WritingMode wm = frame->GetWritingMode();
+    LogicalSize availSize = parentReflowInput.ComputedSize(wm);
+    availSize.BSize(wm) = NS_UNCONSTRAINEDSIZE;
+    MOZ_ASSERT(frame->GetParent()->FirstInFlow() ==
+                   parentReflowInput.mFrame->FirstInFlow(),
+               "bad logic in this function");
+    new (reflowInputs + i)
+        ReflowInput(presContext, parentReflowInput, frame, availSize);
+  }
+
+  MOZ_ASSERT(reflowInputs[len - 1].mFrame == aDescendantFrame,
+             "bad logic in this function");
+  nscoord result = reflowInputs[len - 1].ComputedISize();
+
+  for (uint32_t i = len; i-- != 0;) {
+    reflowInputs[i].~ReflowInput();
+  }
+  free(reflowInputs);
+
+  return result;
+}
+
+void nsFontInflationData::UpdateISize(const ReflowInput& aReflowInput) {
+  nsIFrame* bfc = aReflowInput.mFrame;
+  NS_ASSERTION(bfc->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT),
+               "must be block formatting context");
+
+  nsIFrame* firstInflatableDescendant =
+      FindEdgeInflatableFrameIn(bfc, eFromStart);
+  if (!firstInflatableDescendant) {
+    mTextAmount = 0;
+    mTextThreshold = 0;  // doesn't matter
+    mTextDirty = false;
+    mInflationEnabled = false;
+    return;
+  }
+  nsIFrame* lastInflatableDescendant = FindEdgeInflatableFrameIn(bfc, eFromEnd);
+  MOZ_ASSERT(!firstInflatableDescendant == !lastInflatableDescendant,
+             "null-ness should match; NearestCommonAncestorFirstInFlow"
+             " will crash when passed null");
+
+  // Particularly when we're computing for the root BFC, the inline-size of
+  // nca might differ significantly for the inline-size of bfc.
+  nsIFrame* nca = NearestCommonAncestorFirstInFlow(
+      firstInflatableDescendant, lastInflatableDescendant, bfc);
+  while (!nca->IsContainerForFontSizeInflation()) {
+    nca = nca->GetParent()->FirstInFlow();
+  }
+
+  nscoord newNCAISize = ComputeDescendantISize(aReflowInput, nca);
+
+  // See comment above "font.size.inflation.lineThreshold" in
+  // modules/libpref/src/init/StaticPrefList.yaml .
+  PresShell* presShell = bfc->PresShell();
+  uint32_t lineThreshold = presShell->FontSizeInflationLineThreshold();
+  nscoord newTextThreshold = (newNCAISize * lineThreshold) / 100;
+
+  if (mTextThreshold <= mTextAmount && mTextAmount < newTextThreshold) {
+    // Because we truncate our scan when we hit sufficient text, we now
+    // need to rescan.
+    mTextDirty = true;
+  }
+
+  // Font inflation increases the font size for a given flow root so that the
+  // text is legible when we've zoomed such that the respective nearest common
+  // ancestor's (NCA) full inline-size (ISize) fills the screen. We assume how-
+  // ever that we don't want to zoom out further than the root iframe's ISize
+  // (i.e. the viewport for a top-level document, or the containing iframe
+  // otherwise), since in some cases zooming out further might not even be
+  // possible or make sense.
+  // Hence the ISize assumed to be usable for displaying text is limited to the
+  // visible area.
+  nsPresContext* presContext = bfc->PresContext();
+  MOZ_ASSERT(
+      bfc->GetWritingMode().IsVertical() == nca->GetWritingMode().IsVertical(),
+      "writing mode of NCA should match that of its flow root");
+  nscoord iFrameISize = bfc->GetWritingMode().IsVertical()
+                            ? presContext->GetVisibleArea().height
+                            : presContext->GetVisibleArea().width;
+  mUsableISize = std::min(iFrameISize, newNCAISize);
+  mTextThreshold = newTextThreshold;
+  mInflationEnabled = mTextAmount >= mTextThreshold;
+}
+
+/* static */ nsIFrame* nsFontInflationData::FindEdgeInflatableFrameIn(
+    nsIFrame* aFrame, SearchDirection aDirection) {
+  // NOTE: This function has a similar structure to ScanTextIn!
+
+  // FIXME: Should probably only scan the text that's actually going to
+  // be inflated!
+
+  nsIFormControlFrame* fcf = do_QueryFrame(aFrame);
+  if (fcf) {
+    return aFrame;
+  }
+
+  // FIXME: aDirection!
+  AutoTArray<FrameChildList, 4> lists;
+  aFrame->GetChildLists(&lists);
+  for (uint32_t i = 0, len = lists.Length(); i < len; ++i) {
+    const nsFrameList& list =
+        lists[(aDirection == eFromStart) ? i : len - i - 1].mList;
+    for (nsIFrame* kid = (aDirection == eFromStart) ? list.FirstChild()
+                                                    : list.LastChild();
+         kid; kid = (aDirection == eFromStart) ? kid->GetNextSibling()
+                                               : kid->GetPrevSibling()) {
+      if (kid->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT)) {
+        // Goes in a different set of inflation data.
+        continue;
+      }
+
+      if (kid->IsTextFrame()) {
+        nsIContent* content = kid->GetContent();
+        if (content && kid == content->GetPrimaryFrame()) {
+          uint32_t len = nsTextFrameUtils::
+              ComputeApproximateLengthWithWhitespaceCompression(
+                  content->AsText(), kid->StyleText());
+          if (len != 0) {
+            return kid;
+          }
+        }
+      } else {
+        nsIFrame* kidResult = FindEdgeInflatableFrameIn(kid, aDirection);
+        if (kidResult) {
+          return kidResult;
+        }
+      }
+    }
+  }
+
+  return nullptr;
+}
+
+void nsFontInflationData::ScanText() {
+  mTextDirty = false;
+  mTextAmount = 0;
+  ScanTextIn(mBFCFrame);
+  mInflationEnabled = mTextAmount >= mTextThreshold;
+}
+
+static uint32_t DoCharCountOfLargestOption(nsIFrame* aContainer) {
+  uint32_t result = 0;
+  for (nsIFrame* option : aContainer->PrincipalChildList()) {
+    uint32_t optionResult;
+    if (option->GetContent()->IsHTMLElement(nsGkAtoms::optgroup)) {
+      optionResult = DoCharCountOfLargestOption(option);
+    } else {
+      // REVIEW: Check the frame structure for this!
+      optionResult = 0;
+      for (nsIFrame* optionChild : option->PrincipalChildList()) {
+        if (optionChild->IsTextFrame()) {
+          optionResult += nsTextFrameUtils::
+              ComputeApproximateLengthWithWhitespaceCompression(
+                  optionChild->GetContent()->AsText(),
+                  optionChild->StyleText());
+        }
+      }
+    }
+    if (optionResult > result) {
+      result = optionResult;
+    }
+  }
+  return result;
+}
+
+static uint32_t CharCountOfLargestOption(nsIFrame* aListControlFrame) {
+  return DoCharCountOfLargestOption(
+      static_cast<nsListControlFrame*>(aListControlFrame)
+          ->GetOptionsContainer());
+}
+
+void nsFontInflationData::ScanTextIn(nsIFrame* aFrame) {
+  // NOTE: This function has a similar structure to FindEdgeInflatableFrameIn!
+
+  // FIXME: Should probably only scan the text that's actually going to
+  // be inflated!
+
+  for (const auto& childList : aFrame->ChildLists()) {
+    for (nsIFrame* kid : childList.mList) {
+      if (kid->HasAnyStateBits(NS_FRAME_FONT_INFLATION_FLOW_ROOT)) {
+        // Goes in a different set of inflation data.
+        continue;
+      }
+
+      LayoutFrameType fType = kid->Type();
+      if (fType == LayoutFrameType::Text) {
+        nsIContent* content = kid->GetContent();
+        if (content && kid == content->GetPrimaryFrame()) {
+          uint32_t len = nsTextFrameUtils::
+              ComputeApproximateLengthWithWhitespaceCompression(
+                  content->AsText(), kid->StyleText());
+          if (len != 0) {
+            nscoord fontSize = kid->StyleFont()->mFont.size.ToAppUnits();
+            if (fontSize > 0) {
+              mTextAmount += fontSize * len;
+            }
+          }
+        }
+      } else if (fType == LayoutFrameType::TextInput) {
+        // We don't want changes to the amount of text in a text input
+        // to change what we count towards inflation.
+        nscoord fontSize = kid->StyleFont()->mFont.size.ToAppUnits();
+        int32_t charCount = static_cast<nsTextControlFrame*>(kid)->GetCols();
+        mTextAmount += charCount * fontSize;
+      } else if (fType == LayoutFrameType::ComboboxControl) {
+        // See textInputFrame above (with s/amount of text/selected option/).
+        // Don't just recurse down to the list control inside, since we
+        // need to exclude the display frame.
+        nscoord fontSize = kid->StyleFont()->mFont.size.ToAppUnits();
+        int32_t charCount = CharCountOfLargestOption(
+            static_cast<nsComboboxControlFrame*>(kid)->GetDropDown());
+        mTextAmount += charCount * fontSize;
+      } else if (fType == LayoutFrameType::ListControl) {
+        // See textInputFrame above (with s/amount of text/selected option/).
+        nscoord fontSize = kid->StyleFont()->mFont.size.ToAppUnits();
+        int32_t charCount = CharCountOfLargestOption(kid);
+        mTextAmount += charCount * fontSize;
+      } else {
+        // recursive step
+        ScanTextIn(kid);
+      }
+
+      if (mTextAmount >= mTextThreshold) {
+        return;
+      }
+    }
+  }
+}