Bug 1587570 - Remove support for the subscriptshift and superscriptshift attributes. r=emilio

See https://groups.google.com/forum/#!topic/mozilla.dev.platform/CAqw0Nxw6Pg

Differential Revision: https://phabricator.services.mozilla.com/D48766

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

dom/base/nsDeprecatedOperationList.h

@@ -51,5 +51,6 @@ DEPRECATED_OPERATION(MathML_DeprecatedLineThicknessValue)
 DEPRECATED_OPERATION(MathML_DeprecatedMathSizeValue)
 DEPRECATED_OPERATION(MathML_DeprecatedMathSpaceValue)
 DEPRECATED_OPERATION(MathML_DeprecatedMencloseNotationRadical)
+DEPRECATED_OPERATION(MathML_DeprecatedScriptShiftAttributes)
 DEPRECATED_OPERATION(MathML_DeprecatedStyleAttribute)
 DEPRECATED_OPERATION(MathML_DeprecatedXLinkAttribute)

dom/locales/en-US/chrome/dom/dom.properties

@@ -375,6 +375,8 @@ MathML_DeprecatedMathSizeValueWarning=“small”, “normal” and “big” ar
 MathML_DeprecatedMathSpaceValueWarning=“veryverythinmathspace”, “verythinmathspace”, “thinmathspace”, “mediummathspace”, “thickmathspace”, “verythickmathspace” and “veryverythickmathspace” are deprecated values for MathML lengths and will be removed at a future date.
 # LOCALIZATION NOTE: Do not translate radical, notation and menclose.
 MathML_DeprecatedMencloseNotationRadical=The “radical” value is deprecated for the “notation” attribute of the <menclose> element and will be removed at a future date.
+# LOCALIZATION NOTE: Do not translate MathML, subscriptshift and superscriptshift.
+MathML_DeprecatedScriptShiftAttributes=MathML attributes “subscriptshift” and “superscriptshift” are deprecated and may be removed at a future date.
 # LOCALIZATION NOTE: Do not translate MathML, background, color, fontfamily, fontsize, fontstyle and fontweight.
 MathML_DeprecatedStyleAttributeWarning=MathML attributes “background”, “color”, “fontfamily”, “fontsize”, “fontstyle” and “fontweight” are deprecated and will be removed at a future date.
 # LOCALIZATION NOTE: Do not translate MathML and XLink.

layout/mathml/nsMathMLmmultiscriptsFrame.cpp

@@ -7,6 +7,7 @@
 #include "nsMathMLmmultiscriptsFrame.h"
 
 #include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_mathml.h"
 #include "nsPresContext.h"
 #include <algorithm>
 #include "gfxContext.h"
@@ -94,41 +95,43 @@ nsresult nsMathMLmmultiscriptsFrame::Place(DrawTarget* aDrawTarget,
   nscoord supScriptShift = 0;
   float fontSizeInflation = nsLayoutUtils::FontSizeInflationFor(this);
 
-  // subscriptshift
-  //
-  // "Specifies the minimum amount to shift the baseline of subscript down; the
-  // default is for the rendering agent to use its own positioning rules."
-  //
-  // values: length
-  // default: automatic
-  //
-  // We use 0 as the default value so unitless values can be ignored.
-  // As a minimum, negative values can be ignored.
-  //
-  nsAutoString value;
-  if (!mContent->IsMathMLElement(nsGkAtoms::msup_)) {
-    mContent->AsElement()->GetAttr(kNameSpaceID_None,
-                                   nsGkAtoms::subscriptshift_, value);
-    if (!value.IsEmpty()) {
+  if (!StaticPrefs::mathml_script_shift_attributes_disabled()) {
+    // subscriptshift
+    //
+    // "Specifies the minimum amount to shift the baseline of subscript down;
+    // the default is for the rendering agent to use its own positioning rules."
+    //
+    // values: length
+    // default: automatic
+    //
+    // We use 0 as the default value so unitless values can be ignored.
+    // As a minimum, negative values can be ignored.
+    //
+    nsAutoString value;
+    if (!mContent->IsMathMLElement(nsGkAtoms::msup_) &&
+        mContent->AsElement()->GetAttr(kNameSpaceID_None,
+                                       nsGkAtoms::subscriptshift_, value)) {
+      mContent->OwnerDoc()->WarnOnceAbout(
+          dom::Document::eMathML_DeprecatedScriptShiftAttributes);
       ParseNumericValue(value, &subScriptShift, 0, PresContext(),
                         mComputedStyle, fontSizeInflation);
     }
-  }
-  // superscriptshift
-  //
-  // "Specifies the minimum amount to shift the baseline of superscript up; the
-  // default is for the rendering agent to use its own positioning rules."
-  //
-  // values: length
-  // default: automatic
-  //
-  // We use 0 as the default value so unitless values can be ignored.
-  // As a minimum, negative values can be ignored.
-  //
-  if (!mContent->IsMathMLElement(nsGkAtoms::msub_)) {
-    mContent->AsElement()->GetAttr(kNameSpaceID_None,
-                                   nsGkAtoms::superscriptshift_, value);
-    if (!value.IsEmpty()) {
+    // superscriptshift
+    //
+    // "Specifies the minimum amount to shift the baseline of superscript up;
+    // the default is for the rendering agent to use its own positioning rules."
+    //
+    // values: length
+    // default: automatic
+    //
+    // We use 0 as the default value so unitless values can be ignored.
+    // As a minimum, negative values can be ignored.
+    //
+    if (!mContent->IsMathMLElement(nsGkAtoms::msub_) &&
+        mContent->AsElement()->GetAttr(kNameSpaceID_None,
+                                       nsGkAtoms::superscriptshift_, value)) {
+      mContent->OwnerDoc()->WarnOnceAbout(
+          dom::Document::eMathML_DeprecatedScriptShiftAttributes);
       ParseNumericValue(value, &supScriptShift, 0, PresContext(),
                         mComputedStyle, fontSizeInflation);
     }

layout/mathml/tests/test_bug827713.html

@@ -34,24 +34,26 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=706406
   </math></p>
 <pre id="test">
 <script type="application/javascript">
-
     /** Test for the scriptshift aspect of bug 827713 **/
     SimpleTest.waitForExplicitFinish();
 
-    subBaseRect = $("subbase").getBoundingClientRect();
-    subSubRect = $("subsub").getBoundingClientRect();
-    is(subBaseRect.bottom, subSubRect.top, "Bad subscript shift for msub");
+    if (SpecialPowers.getBoolPref('mathml.script_shift_attributes.disabled')) {
+      ok(true, "Script shifts disabled");
+    } else {
+      subBaseRect = $("subbase").getBoundingClientRect();
+      subSubRect = $("subsub").getBoundingClientRect();
+      is(subBaseRect.bottom, subSubRect.top, "Bad subscript shift for msub");
 
-    supBaseRect = $("supbase").getBoundingClientRect();
-    supSupRect = $("supsup").getBoundingClientRect();
-    is(supBaseRect.top, supSupRect.bottom, "Bad superscript shift for msup");
-
-    ssBaseRect = $("ssbase").getBoundingClientRect();
-    ssSubRect = $("sssub").getBoundingClientRect();
-    ssSupRect = $("sssup").getBoundingClientRect();
-    is(ssBaseRect.bottom, ssSubRect.top, "Bad subscript shift for msubusp");
-    is(ssBaseRect.top, ssSupRect.bottom, "Bad superscript shift for msubusp");
+      supBaseRect = $("supbase").getBoundingClientRect();
+      supSupRect = $("supsup").getBoundingClientRect();
+      is(supBaseRect.top, supSupRect.bottom, "Bad superscript shift for msup");
 
+      ssBaseRect = $("ssbase").getBoundingClientRect();
+      ssSubRect = $("sssub").getBoundingClientRect();
+      ssSupRect = $("sssup").getBoundingClientRect();
+      is(ssBaseRect.bottom, ssSubRect.top, "Bad subscript shift for msubusp");
+      is(ssBaseRect.top, ssSupRect.bottom, "Bad superscript shift for msubusp");
+    }
 
     SimpleTest.finish();
 

modules/libpref/init/StaticPrefList.yaml

@@ -5364,6 +5364,12 @@
   value: @IS_NIGHTLY_BUILD@
   mirror: always
 
+# Whether to disable subscriptshift and superscriptshift attributes.
+- name: mathml.script_shift_attributes.disabled
+  type: bool
+  value: @IS_NIGHTLY_BUILD@
+  mirror: always
+
 # Whether to disable support for XLink on MathML elements.
 - name: mathml.xlink.disabled
   type: bool