Fixed intial font-size - now set to 1em

- added basic support for "medium", "small" etc. font-size values
- fixes #419

Source/DataTypes/SvgUnitConverter.cs

@@ -32,6 +32,23 @@ namespace Svg
             if (unit == "none")
                 return SvgUnit.None;
 
+            // Note: these are ad-hoc values based on a factor of about 1.2 between adjacent values
+            // see https://www.w3.org/TR/CSS2/fonts.html#value-def-absolute-size for more information
+            if (unit == "medium")
+                unit = "1em";
+            else if (unit == "small")
+                unit = "0.8em";
+            else if (unit == "x-small")
+                unit = "0.7em";
+            else if (unit == "xx-small")
+                unit = "0.6em";
+            else if (unit == "large")
+                unit = "1.2em";
+            else if (unit == "x-large")
+                unit = "1.4em";
+            else if (unit == "xx-large")
+                unit = "1.7em";
+
             for (int i = 0; i < unit.Length; i++)
             {
                 // If the character is a percent sign or a letter which is not an exponent 'e'

Source/SvgElementStyle.cs

@@ -361,7 +361,7 @@ namespace Svg
             var fontSizeUnit = this.FontSize;
             if (fontSizeUnit == SvgUnit.None || fontSizeUnit == SvgUnit.Empty)
             {
-                fontSize = 1.0f;
+                fontSize = new SvgUnit(SvgUnitType.Em, 1.0f);
             }
             else
             {

Tests/Svg.UnitTests/PassingTests.csv

@@ -199,6 +199,7 @@ __issue-345-01
 __issue-354-01
 __issue-385-01_Test_text-anchor-middle
 __issue-398-01
+__issue-419-01
 __pull_request-373-01
 __pull_request-374-01
 __pull_request-414-01

Tests/W3CTestSuite/svg/__issue-419-01.svg

+<?xml version="1.0" encoding="utf-8" standalone="no"?>
+<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" id="seatplan">
+  <rect id="stage" x="100" y="50" width="100" height="50" fill="white" stroke="black" />
+  <text x="130" y="80" text-anchor="middle" fill="black">Stage</text>
+</svg>
\ No newline at end of file