handle case where offsets are out of range

default to returning empty glyph where the offset is out of the
file length range, this fixes file 12623 where the truetype file
is completely broken

src/UglyToad.PdfPig.Fonts/TrueType/Tables/GlyphDataTable.cs

@@ -121,14 +121,23 @@
 
             for (var i = 0; i < glyphCount; i++)
             {
-                if (offsets[i + 1] <= offsets[i])
+                var offset = offsets[i];
+
+                if (offsets[i + 1] <= offset)
                 {
                     // empty glyph
                     result[i] = emptyGlyph;
                     continue;
                 }
 
-                data.Seek(offsets[i]);
+                // Invalid table, just sub in the empty glyph
+                if (offset >= data.Length)
+                {
+                    result[i] = emptyGlyph;
+                    continue;
+                }
+
+                data.Seek(offset);
 
                 var contourCount = data.ReadSignedShort();
 

src/UglyToad.PdfPig.Tests/Fonts/TrueType/Parser/TrueTypeFontParserTests.cs

@@ -229,5 +229,19 @@ namespace UglyToad.PdfPig.Tests.Fonts.TrueType.Parser
             Assert.NotNull(font.TableRegister.NameTable);
             Assert.NotEmpty(font.TableRegister.NameTable.NameRecords);
         }
+
+        [Fact]
+        public void Parse12623CorruptFileAndGetGlyphs()
+        {
+            var bytes = TrueTypeTestHelper.GetFileBytes("corrupt-12623");
+
+            var input = new TrueTypeDataBytes(new MemoryInputBytes(bytes));
+
+            var font = TrueTypeFontParser.Parse(input);
+
+            Assert.NotNull(font);
+
+            font.TryGetPath(1, out _);
+        }
     }
 }

src/UglyToad.PdfPig.Tests/UglyToad.PdfPig.Tests.csproj

@@ -39,11 +39,7 @@
     </ItemGroup>
 
     <ItemGroup>
-        <EmbeddedResource Remove="Fonts\TrueType\Andada-Regular.ttf" />
+        <EmbeddedResource Remove="Fonts\TrueType\*.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\google-simple-doc.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\issue-258-corrupt-name-table.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\PMingLiU.ttf" />
-        <EmbeddedResource Remove="Fonts\TrueType\Roboto-Regular.ttf" />
         <EmbeddedResource Remove="Fonts\Type1\AdobeUtopia.pfa" />
         <EmbeddedResource Remove="Fonts\Type1\CMBX10.pfa" />
         <EmbeddedResource Remove="Fonts\Type1\CMBX12.pfa" />
@@ -61,24 +57,12 @@
         <Content Include="Fonts\CompactFontFormat\MinionPro.bin">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </Content>
-        <Content Include="Fonts\TrueType\Andada-Regular.ttf">
+        <Content Include="Fonts\TrueType\*.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
-        <Content Include="Fonts\TrueType\google-simple-doc.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
-        <Content Include="Fonts\TrueType\issue-258-corrupt-name-table.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
-        <Content Include="Fonts\TrueType\PMingLiU.ttf">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </Content>
         <Content Include="Fonts\TrueType\Roboto-Regular.GlyphData.txt">
             <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
         </Content>
-        <Content Include="Fonts\TrueType\Roboto-Regular.ttf">
-            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-        </Content>
         <Content Include="Fonts\Type1\AdobeUtopia.pfa" />
         <Content Include="Fonts\Type1\CMBX10.pfa" />
         <Content Include="Fonts\Type1\CMBX12.pfa" />