Bug 1697980 - Implement new uppercase mapping of eszett (U+00DF) to U+1E9E, but preffed-off by default due to inconsistent font support. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D175620
2023-04-18 07:06:09 +00:00 · 2023-04-18 07:06:09 +00:00 · 0026f56411
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@ -333,6 +333,7 @@ static const char* gExactCallbackPrefs[] = {
    "intl.accept_languages",
    "layout.css.devPixelsPerPx",
    "layout.css.dpi",
+    "layout.css.text-transform.uppercase-eszett.enabled",
    "privacy.trackingprotection.enabled",
    "ui.use_standins_for_native_colors",
    nullptr,
@ -613,6 +614,11 @@ void nsPresContext::PreferenceChanged(const char* aPrefName) {
    }
  }

+  if (prefName.EqualsLiteral(
+          "layout.css.text-transform.uppercase-eszett.enabled")) {
+    changeHint |= NS_STYLE_HINT_REFLOW;
+  }
+
  // We will end up calling InvalidatePreferenceSheets one from each pres
  // context, but all it's doing is clearing its cached sheet pointers, so it
  // won't be wastefully recreating the sheet multiple times.
--- a/layout/generic/nsTextRunTransformations.cpp
+++ b/layout/generic/nsTextRunTransformations.cpp
@ -12,6 +12,7 @@
 #include "IrishCasing.h"
 #include "mozilla/ComputedStyleInlines.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/TextEditor.h"
 #include "mozilla/gfx/2D.h"
 #include "nsGkAtoms.h"
@ -622,6 +623,16 @@ bool nsCaseTransformTextRunFactory::TransformString(
            // to check for special uppercase (ß)
          }

+          // Updated mapping for German eszett, not currently reflected in the
+          // Unicode data files. This is behind a pref, as it may not work well
+          // with many (esp. older) fonts.
+          if (ch == 0x00DF &&
+              StaticPrefs::
+                  layout_css_text_transform_uppercase_eszett_enabled()) {
+            ch = 0x1E9E;
+            break;
+          }
+
          mcm = mozilla::unicode::SpecialUpper(ch);
          if (mcm) {
            int j = 0;
--- a/layout/reftests/text-transform/reftest.list
+++ b/layout/reftests/text-transform/reftest.list
@ -42,5 +42,8 @@ fuzzy(0-1,0-80) == all-title.html all-title-ref.html
 == fullwidth-2.html fullwidth-2-ref.html
 == fullwidth-all.html fullwidth-all-ref.html

+pref(layout.css.text-transform.uppercase-eszett.enabled,false) == uppercase-eszett-1.html uppercase-eszett-1a-ref.html
+pref(layout.css.text-transform.uppercase-eszett.enabled,true)  == uppercase-eszett-1.html uppercase-eszett-1b-ref.html
+
 # Reset default prefs
 defaults
--- a/layout/reftests/text-transform/uppercase-eszett-1.html
+++ b/layout/reftests/text-transform/uppercase-eszett-1.html
@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<div style="text-transform: uppercase;">
+Straße
+Großmann
--- a/layout/reftests/text-transform/uppercase-eszett-1a-ref.html
+++ b/layout/reftests/text-transform/uppercase-eszett-1a-ref.html
@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<div>
+STRASSE
+GROSSMANN
--- a/layout/reftests/text-transform/uppercase-eszett-1b-ref.html
+++ b/layout/reftests/text-transform/uppercase-eszett-1b-ref.html
@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<meta charset=utf-8>
+<div>
+STRAẞE
+GROẞMANN
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@ -8964,6 +8964,12 @@
  value: 50 # 50%
  mirror: always

+# Whether the "modern" uppercase mapping of ß to ẞ (rather than SS) is used.
+- name: layout.css.text-transform.uppercase-eszett.enabled
+  type: bool
+  value: false
+  mirror: always
+
 # Whether to block large cursors intersecting UI.
 - name: layout.cursor.block.enabled
  type: bool