SVGTextElement.getSubStringLength returns wrong result (affects Acid3)

[Eric Seidel (no email)]

SVGTextElement.getSubStringLength returns wrong result (affects Acid3)

Now that the SVGDocument mimetype issue has been fixed, we fail Test 78 in a new way:

Test 78: expected: 42, got: 65 - getSubStringLength #1 failed.

    function () {
      // test 78: external SVG fonts, from Erik Dahlstrom
      //
      // SVGFonts are described here[3], and the relevant DOM methods
      // used in the test are defined here[4].
      //
      // Note that in order to be more predictable the svg should be
      // visible, so that clause "For non-rendering environments, the
      // user agent shall make reasonable assumptions about glyph
      // metrics." doesn't influence the results. We use 'opacity:0'
      // to hide the SVG, but arguably it's still a "rendering
      // environment".
      //
      // The font-size 4000 was chosen because that matches the
      // unitsPerEm value in the svgfont, which makes it easy to check
      // the glyph advances since they will then be exactly what was
      // specified in the svgfont.
      //
      // [3] http://www.w3.org/TR/SVG11/fonts.html
      // [4] http://www.w3.org/TR/SVG11/text.html#InterfaceSVGTextContentElement

      var svgns = "http://www.w3.org/2000/svg";
      var xlinkns = "http://www.w3.org/1999/xlink";
      var svgdoc = kungFuDeathGrip.firstChild.contentDocument;
      assert(svgdoc, "contentDocument failed on <object> for svg document.");
      var svg = svgdoc.documentElement;
      var text = svgdoc.createElementNS(svgns, "text");
      text.setAttribute("y", "1em");
      text.setAttribute("font-size", "4000");
      text.setAttribute("font-family", "ACID3svgfont");
      var textContent = svgdoc.createTextNode("abc");
      text.appendChild(textContent);
      svg.appendChild(text);
      // The font-size 4000 was chosen because that matches the unitsPerEm value in the svgfont, 
      // which makes it easy to check the glyph advances since they will then be exactly what was specified in the svgfont.
      assert(text.getNumberOfChars, "SVGTextContentElement.getNumberOfChars() not supported.");
      assertEquals(text.getNumberOfChars(), 3, "getNumberOfChars returned incorrect string length.");
      assertEquals(text.getComputedTextLength(), 4711+42+23, "getComputedTextLength failed.");
      assertEquals(text.getSubStringLength(0,1), 42, "getSubStringLength #1 failed.");
      assertEquals(text.getSubStringLength(0,2), 42+23, "getSubStringLength #2 failed.");
      assertEquals(text.getSubStringLength(1,1), 23, "getSubStringLength #3 failed.");
      assertEquals(text.getSubStringLength(1,0), 0, "getSubStringLength #4 failed.");
      var code = -1000;
      try {
        var sl = text.getSubStringLength(1,3);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getSubStringLength #1 didn't throw exception.");
      code = -1000;
      try {
        var sl = text.getSubStringLength(0,3);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getSubStringLength #2 didn't throw exception.");
      code = -1000;
      try {
        var sl = text.getSubStringLength(1,2);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getSubStringLength #3 didn't throw exception.");
      code = -1000;
      try {
        var sl = text.getSubStringLength(-17,20);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getSubStringLength #4 didn't throw exception.");
      code = -1000;
      try {
        var sl = text.getSubStringLength(1,2);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getSubStringLength #5 didn't throw exception.");
      assertEquals(text.getStartPositionOfChar(0).x, 0, "getStartPositionOfChar(0).x returned invalid value.");
      assertEquals(text.getStartPositionOfChar(1).x, 42, "getStartPositionOfChar(1).x returned invalid value.");
      assertEquals(text.getStartPositionOfChar(2).x, 42+23, "getStartPositionOfChar(2).x returned invalid value.");
      assertEquals(text.getStartPositionOfChar(0).y, 4000, "getStartPositionOfChar(0).y returned invalid value.");
      code = -1000;
      try {
        var val = text.getStartPositionOfChar(-1);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getStartPositionOfChar #1 exception failed.");
      code = -1000;
      try {
        var val = text.getStartPositionOfChar(4);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getStartPositionOfChar #2 exception failed.");
      assertEquals(text.getEndPositionOfChar(0).x, 42, "getEndPositionOfChar(0).x returned invalid value.");
      assertEquals(text.getEndPositionOfChar(1).x, 42+23, "getEndPositionOfChar(1).x returned invalid value.");
      assertEquals(text.getEndPositionOfChar(2).x, 42+23+4711, "getEndPositionOfChar(2).x returned invalid value.");
      code = -1000;
      try {
        var val = text.getEndPositionOfChar(-17);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getEndPositionOfChar #1 exception failed.");
      code = -1000;
      try {
        var val = text.getEndPositionOfChar(4);
      } catch(e) {
        code = e.code;
      }
      assertEquals(code, DOMException.INDEX_SIZE_ERR, "getEndPositionOfChar #2 exception failed.");
      return 5;
    },

[Eric Seidel (no email)]

*** This bug has been marked as a duplicate of 17078 ***