Bug 1573268 - Convert font.size.inflation.lineThreshold to a static pref. r=njn

Converts font.size.inflation.lineThreshold varcache pref to a static pref. Like previous revisions, this retains the member variable in PresShell.

Differential Revision: https://phabricator.services.mozilla.com/D41662

--HG--
extra : moz-landing-system : lando

layout/base/PresShell.cpp

@@ -1036,7 +1036,7 @@ void PresShell::Init(Document* aDocument, nsPresContext* aPresContext,
   mFontSizeInflationEmPerLine = StaticPrefs::font_size_inflation_emPerLine();
   mFontSizeInflationMinTwips = StaticPrefs::font_size_inflation_minTwips();
   mFontSizeInflationLineThreshold =
-      nsLayoutUtils::FontSizeInflationLineThreshold();
+      StaticPrefs::font_size_inflation_lineThreshold();
   mFontSizeInflationForceEnabled =
       nsLayoutUtils::FontSizeInflationForceEnabled();
   mFontSizeInflationDisabledInMasterProcess =

layout/base/nsLayoutUtils.cpp

@@ -183,8 +183,6 @@ bool nsLayoutUtils::gPreventAssertInCompareTreePosition = false;
 typedef ScrollableLayerGuid::ViewID ViewID;
 typedef nsStyleTransformMatrix::TransformReferenceBox TransformReferenceBox;
 
-/* static */
-uint32_t nsLayoutUtils::sFontSizeInflationLineThreshold;
 /* static */
 bool nsLayoutUtils::sFontSizeInflationForceEnabled;
 /* static */
@@ -7979,8 +7977,6 @@ size_t nsLayoutUtils::SizeOfTextRunsForFrames(nsIFrame* aFrame,
 
 /* static */
 void nsLayoutUtils::Initialize() {
-  Preferences::AddUintVarCache(&sFontSizeInflationLineThreshold,
-                               "font.size.inflation.lineThreshold");
   Preferences::AddBoolVarCache(&sFontSizeInflationForceEnabled,
                                "font.size.inflation.forceEnabled");
   Preferences::AddBoolVarCache(&sFontSizeInflationDisabledInMasterProcess,

layout/base/nsLayoutUtils.h

@@ -2445,14 +2445,6 @@ class nsLayoutUtils {
 
   static bool FontSizeInflationEnabled(nsPresContext* aPresContext);
 
-  /**
-   * See comment above "font.size.inflation.lineThreshold" in
-   * modules/libpref/src/init/all.js .
-   */
-  static uint32_t FontSizeInflationLineThreshold() {
-    return sFontSizeInflationLineThreshold;
-  }
-
   static bool FontSizeInflationForceEnabled() {
     return sFontSizeInflationForceEnabled;
   }
@@ -3025,7 +3017,6 @@ class nsLayoutUtils {
       const nsIFrame* aFrame);
 
  private:
-  static uint32_t sFontSizeInflationLineThreshold;
   static bool sFontSizeInflationForceEnabled;
   static bool sFontSizeInflationDisabledInMasterProcess;
   static uint32_t sSystemFontScale;

layout/generic/nsFontInflationData.cpp

@@ -194,7 +194,7 @@ void nsFontInflationData::UpdateISize(const ReflowInput& aReflowInput) {
   nscoord newNCAISize = ComputeDescendantISize(aReflowInput, nca);
 
   // See comment above "font.size.inflation.lineThreshold" in
-  // modules/libpref/src/init/all.js .
+  // modules/libpref/src/init/StaticPrefList.yaml .
   PresShell* presShell = bfc->PresShell();
   uint32_t lineThreshold = presShell->FontSizeInflationLineThreshold();
   nscoord newTextThreshold = (newNCAISize * lineThreshold) / 100;

modules/libpref/init/StaticPrefList.yaml

@@ -2579,6 +2579,30 @@
   value: 1
   mirror: always
 
+# Since the goal of font size inflation is to avoid having to
+# repeatedly scroll side to side to read a block of text, and there are
+# a number of page layouts where a relatively small chunk of text is
+# better off not being inflated according to the same algorithm we use
+# for larger chunks of text, we want a threshold for an amount of text
+# that triggers font size inflation.  This preference controls that
+# threshold.
+#
+# It controls the threshold used within an *approximation* of the
+# number of lines of text we use.  In particular, if we assume that
+# each character (collapsing collapsible whitespace) has a width the
+# same as the em-size of the font (when, normally, it's actually quite
+# a bit smaller on average), this preference gives the percentage of a
+# number of lines of text we'd need to trigger inflation.  This means
+# that a percentage of 100 means that we'd need a number of characters
+# (we know the font size and the width) equivalent to one line of
+# square text (which is actually a lot less than a real line of text).
+#
+# A value of 0 means there's no character length threshold.
+- name: font.size.inflation.lineThreshold
+  type: uint32_t
+  value: 400
+  mirror: always
+
 # This controls the percentage that fonts will be inflated, if font
 # size inflation is enabled. Essentially, if we have a specified font
 # size, s, and an inflated font size, i, this specifies that the ratio

modules/libpref/init/all.js

@@ -3378,28 +3378,6 @@ pref("font.size.inflation.forceEnabled", false);
  * this pref.
  */
 pref("font.size.inflation.disabledInMasterProcess", false);
-/*
- * Since the goal of font size inflation is to avoid having to
- * repeatedly scroll side to side to read a block of text, and there are
- * a number of page layouts where a relatively small chunk of text is
- * better of not being inflated according to the same algorithm we use
- * for larger chunks of text, we want a threshold for an amount of text
- * that triggers font size inflation.  This preference controls that
- * threshold.
- *
- * It controls the threshold used within an *approximation* of the
- * number of lines of text we use.  In particular, if we assume that
- * each character (collapsing collapsible whitespace) has a width the
- * same as the em-size of the font (when, normally, it's actually quite
- * a bit smaller on average), this preference gives the percentage of a
- * number of lines of text we'd need to trigger inflation.  This means
- * that a percentage of 100 means that we'd need a number of characters
- * (we know the font size and the width) equivalent to one line of
- * square text (which is actually a lot less than a real line of text).
- *
- * A value of 0 means there's no character length threshold.
- */
-pref("font.size.inflation.lineThreshold", 400);
 
 /**
  * This setting corresponds to a global text zoom setting affecting