MathML writer: improve formatting of aligned equations.

An EArray with alternating R,L alignments will be assumed
to be aligned equations and rendered without padding.
Closes #207.

Author: jgm

src/Text/TeXMath/Writers/MathML.hs

@@ -28,7 +28,8 @@ import Text.XML.Light
 import Text.TeXMath.Types
 import Text.TeXMath.Unicode.ToUnicode
 import Data.Generics (everywhere, mkT)
-import Text.TeXMath.Shared (getMMLType, handleDownup, isUppercaseGreek)
+import Text.TeXMath.Shared (getMMLType, handleDownup,
+                            isUppercaseGreek, isRLSequence)
 import Text.TeXMath.Readers.MathML.MMLDict (getMathMLOperator)
 import qualified Data.Text as T
 import Text.Printf
@@ -116,14 +117,20 @@ makeArray tt as ls = unode "mtable" $
    -- see #205 on the need for style attributes:
    where setAlignment AlignLeft    =
            withAttribute "columnalign" "left" .
-           withAttribute "style" "text-align: left"
+           withAttribute "style"
+             (if isRLSequence as
+                 then "text-align: left; padding-left: 0"
+                 else "text-align: left")
          setAlignment AlignRight   =
            withAttribute "columnalign" "right" .
-           withAttribute "style" "text-align: right"
+           withAttribute "style"
+             (if isRLSequence as
+                 then "text-align: right; padding-right: 0"
+                 else "text-align: right")
          setAlignment AlignCenter  =
            withAttribute "columnalign" "center" .
            withAttribute "style" "text-align: center"
-         as'                       = as ++ cycle [AlignCenter]
+         as'                       = as ++ repeat AlignCenter
 
 -- Kept as String for Text.XML.Light
 withAttribute :: String -> T.Text -> Element -> Element

test/writer/mml/sphere_volume.test

@@ -155,7 +155,7 @@
     <mo stretchy="false" form="postfix">}</mo>
     <mtable>
       <mtr>
-        <mtd columnalign="right" style="text-align: right">
+        <mtd columnalign="right" style="text-align: right; padding-right: 0">
           <mrow>
             <mi mathvariant="normal">V</mi>
             <mi mathvariant="normal">o</mi>
@@ -165,7 +165,7 @@
             <mi mathvariant="normal">e</mi>
           </mrow>
         </mtd>
-        <mtd columnalign="left" style="text-align: left">
+        <mtd columnalign="left" style="text-align: left; padding-left: 0">
           <mo>=</mo>
           <munder>
             <mo>∭</mo>
@@ -191,8 +191,8 @@
         </mtd>
       </mtr>
       <mtr>
-        <mtd columnalign="right" style="text-align: right" />
-        <mtd columnalign="left" style="text-align: left">
+        <mtd columnalign="right" style="text-align: right; padding-right: 0" />
+        <mtd columnalign="left" style="text-align: left; padding-left: 0">
           <mo>=</mo>
           <msubsup>
             <mo>∫</mo>
@@ -234,8 +234,8 @@
         </mtd>
       </mtr>
       <mtr>
-        <mtd columnalign="right" style="text-align: right" />
-        <mtd columnalign="left" style="text-align: left">
+        <mtd columnalign="right" style="text-align: right; padding-right: 0" />
+        <mtd columnalign="left" style="text-align: left; padding-left: 0">
           <mo>=</mo>
           <mi>ϕ</mi>
           <msubsup>
@@ -278,8 +278,8 @@
         </mtd>
       </mtr>
       <mtr>
-        <mtd columnalign="right" style="text-align: right" />
-        <mtd columnalign="left" style="text-align: left">
+        <mtd columnalign="right" style="text-align: right; padding-right: 0" />
+        <mtd columnalign="left" style="text-align: left; padding-left: 0">
           <mo>=</mo>
           <mn>2</mn>
           <mi>π</mi>
@@ -299,8 +299,8 @@
         </mtd>
       </mtr>
       <mtr>
-        <mtd columnalign="right" style="text-align: right" />
-        <mtd columnalign="left" style="text-align: left">
+        <mtd columnalign="right" style="text-align: right; padding-right: 0" />
+        <mtd columnalign="left" style="text-align: left; padding-left: 0">
           <mo>=</mo>
           <mstyle displaystyle="false">
             <mfrac>