Bug 1231404 - SubscriptBaselineDropMin or SuperscriptBaselineDropMax are not read from the MATH table. r=jfkthame

layout/mathml/nsMathMLmmultiscriptsFrame.cpp

@@ -203,6 +203,14 @@ nsMathMLmmultiscriptsFrame::PlaceMultiScript(nsPresContext*  aPresContext,
     scriptSpace = nsPresContext::CSSPointsToAppUnits(0.5f);
   }
 
+  // Try and read sub and sup drops from the MATH table.
+  if (mathFont) {
+    subDrop = mathFont->
+      GetMathConstant(gfxFontEntry::SubscriptBaselineDropMin, oneDevPixel);
+    supDrop = mathFont->
+      GetMathConstant(gfxFontEntry::SuperscriptBaselineDropMax, oneDevPixel);
+  }
+
   // force the scriptSpace to be at least 1 pixel
   nscoord onePixel = nsPresContext::CSSPixelsToAppUnits(1);
   scriptSpace = std::max(onePixel, scriptSpace);
@@ -390,8 +398,11 @@ nsMathMLmmultiscriptsFrame::PlaceMultiScript(nsPresContext*  aPresContext,
         // subscript
         subScriptFrame = childFrame;
         GetReflowAndBoundingMetricsFor(subScriptFrame, subScriptSize, bmSubScript);
-        // get the subdrop from the subscript font
-        GetSubDropFromChild (subScriptFrame, subDrop, aFontSizeInflation);
+        if (!mathFont) {
+          // get the subdrop from the subscript font
+          GetSubDropFromChild (subScriptFrame, subDrop, aFontSizeInflation);
+        }
+
         // parameter v, Rule 18a, App. G, TeXbook
         minSubScriptShift = bmBase.descent + subDrop;
         trySubScriptShift = std::max(minSubScriptShift,subScriptShift);
@@ -431,8 +442,10 @@ nsMathMLmmultiscriptsFrame::PlaceMultiScript(nsPresContext*  aPresContext,
         // supscript
         supScriptFrame = childFrame;
         GetReflowAndBoundingMetricsFor(supScriptFrame, supScriptSize, bmSupScript);
-        // get the supdrop from the supscript font
-        GetSupDropFromChild (supScriptFrame, supDrop, aFontSizeInflation);
+        if (!mathFont) {
+          // get the supdrop from the supscript font
+          GetSupDropFromChild (supScriptFrame, supDrop, aFontSizeInflation);
+        }
         // parameter u, Rule 18a, App. G, TeXbook
         minSupScriptShift = bmBase.ascent - supDrop;
         nscoord superscriptBottomMin;

layout/mathml/tests/test_opentype-scripts.html

@@ -9,7 +9,7 @@
     <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
     <meta charset="utf-8"/>
     <style type="text/css">
-      math {
+      math, mspace {
         font-size: 10px;
       }
       @font-face {
@@ -44,6 +44,10 @@
         font-family: scripts-8;
         src: url(/tests/fonts/math/scripts-8.otf);
       }
+      @font-face {
+        font-family: scripts-9;
+        src: url(/tests/fonts/math/scripts-9.otf);
+      }
     </style>
     <script type="text/javascript">
       SimpleTest.waitForExplicitFinish();
@@ -107,6 +111,14 @@
         ok(almostEqual(getBox("ref10").bottom - getBox("sup10").bottom, 9 * 10),
            "Bad SuperscriptBottomMin");
 
+        ok(almostEqual(getBox("base11").bottom + 3 * 10,
+                       getBox("sub11").top),
+           "Bad SubscriptBaselineDrop");
+
+        ok(almostEqual(getBox("base11").top + 5 * 10,
+                       getBox("sup11").bottom),
+           "Bad SuperscriptBaselineDrop");
+
         SimpleTest.finish();
       }
     </script>
@@ -264,5 +276,17 @@
       </math>
     </p>
 
+    <p>
+      <math style="font-family: scripts-9;">
+        <msubsup>
+          <mspace id="base11" height="10em" depth="10em"
+                  width="1em" mathbackground="red"/>
+          <mspace id="sub11"
+                  height="0em" depth="1em" width="1em" mathbackground="green"/>
+          <mspace id="sup11"
+                  height="1em" depth="0em" width="1em" mathbackground="blue"/>
+        </msubsup>
+      </math>
+    </p>
   </body>
 </html>

layout/reftests/fonts/math/generate.py

@@ -479,6 +479,11 @@ f = newMathFont("scripts-8")
 f.math.SuperscriptBottomMin = 9 * em
 saveMathFont(f)
 
+f = newMathFont("scripts-9")
+f.math.SubscriptBaselineDropMin = 3 * em
+f.math.SuperscriptBaselineDropMax = 5 * em
+saveMathFont(f)
+
 ################################################################################
 # Testing Limits Parameters
 f = newMathFont("limits-1")

layout/reftests/fonts/math/mochitest.ini

@@ -31,6 +31,7 @@ support-files =
   /tests/fonts/math/scripts-6.otf
   /tests/fonts/math/scripts-7.otf
   /tests/fonts/math/scripts-8.otf
+  /tests/fonts/math/scripts-9.otf
   /tests/fonts/math/stack-1.otf
   /tests/fonts/math/stack-2.otf
   /tests/fonts/math/stack-3.otf