Fix MathML bug 114909 - dynamically changing the displaystyle attribute in <mstyle> tag doesn't change display

git-svn-id: svn://10.0.0.236/trunk@111791 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/mathml/base/src/nsMathMLmunderFrame.cpp

@@ -105,6 +105,47 @@ nsMathMLmunderFrame::UpdatePresentationData(nsIPresContext* aPresContext,
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsMathMLmunderFrame::UpdatePresentationDataFromChildAt(nsIPresContext* aPresContext,
+                                                       PRInt32         aFirstIndex,
+                                                       PRInt32         aLastIndex,
+                                                       PRInt32         aScriptLevelIncrement,
+                                                       PRUint32        aFlagsValues,
+                                                       PRUint32        aFlagsToUpdate)
+{
+  // munder is special... The REC says:
+  // Within underscript, <munder> always sets displaystyle to "false", 
+  // but increments scriptlevel by 1 only when accentunder is "false".
+  // This means that
+  // 1. don't allow displaystyle to change in the underscript
+  // 2. if the value of the accent is changed, we need to recompute the
+  //    scriptlevel of the underscript. The problem is that the accent
+  //    can change in the <mo> deep down the embellished hierarchy
+
+  // Do #1 here, never allow displaystyle to be changed in the underscript
+  PRInt32 index = 0;
+  nsIFrame* childFrame = mFrames.FirstChild();
+  while (childFrame) {
+    if ((index >= aFirstIndex) &&
+        ((aLastIndex <= 0) || ((aLastIndex > 0) && (index <= aLastIndex)))) {
+      if (index > 0) {
+        // disable the flag
+        aFlagsToUpdate &= ~NS_MATHML_DISPLAYSTYLE;
+        aFlagsValues &= ~NS_MATHML_DISPLAYSTYLE;
+      }
+      PropagatePresentationDataFor(aPresContext, childFrame,
+        aScriptLevelIncrement, aFlagsValues, aFlagsToUpdate);
+    }
+    index++;
+    childFrame->GetNextSibling(&childFrame);
+  }
+  return NS_OK;
+
+  // XXX For #2, if the inner <mo> changes, is has to trigger 
+  // XXX a re-computation of all flags that depend on its state
+  // XXX in the entire embellished hierarchy
+}
+
 NS_IMETHODIMP
 nsMathMLmunderFrame::SetInitialChildList(nsIPresContext* aPresContext,
                                          nsIAtom*        aListName,