[SVGPreview]Handle comments properly (#28863)

* [SVGPreview] Handle comments properly

* f: spelling

* f: add tolerance to the bitmap eq test

* f: remove bitmap eq testing, since it doesn't work on CI for some reason

* f: parsing issue

Author: yuyoyuppe

.github/actions/spell-check/expect.txt

@@ -136,6 +136,7 @@ BITMAPFILEHEADER
 bitmapimage
 BITMAPINFO
 BITMAPINFOHEADER
+Bitmaps
 bitmask
 BITSPIXEL
 bla

src/modules/previewpane/UnitTests-SvgThumbnailProvider/HelperFiles/WithComments.svg

@@ -4,14 +4,12 @@
 
 using System;
 using System.Drawing;
+using System.Drawing.Imaging;
 using System.Runtime.InteropServices;
-using System.Runtime.InteropServices.ComTypes;
 using System.Text;
-using Common.ComInterlop;
 using Microsoft.PowerToys.STATestExtension;
 using Microsoft.PowerToys.ThumbnailHandler.Svg;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
-using Moq;
 
 namespace SvgThumbnailProviderUnitTests
 {
@@ -211,5 +209,17 @@ public void GetThumbnailValidStreamHTML()
 
             Assert.IsTrue(bitmap != null);
         }
+
+        [TestMethod]
+        public void SvgCommentsAreHandledCorrectly()
+        {
+            var filePath = "HelperFiles/WithComments.svg";
+
+            SvgThumbnailProvider svgThumbnailProvider = new SvgThumbnailProvider(filePath);
+
+            Bitmap bitmap = svgThumbnailProvider.GetThumbnail(8);
+
+            Assert.IsTrue(bitmap != null);
+        }
     }
 }

src/modules/previewpane/UnitTests-SvgThumbnailProvider/SvgThumbnailProviderTests.cs

@@ -38,15 +38,19 @@
     <ProjectReference Include="..\SvgThumbnailProvider\SvgThumbnailProvider.csproj" />
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="..\STATestClassAttribute.cs" Link="STATestClassAttribute.cs" />
-    <Compile Include="..\STATestMethodAttribute.cs" Link="STATestMethodAttribute.cs" />
+    <Compile Include="..\STATestClassAttribute.cs"
+      Link="STATestClassAttribute.cs" />
+    <Compile Include="..\STATestMethodAttribute.cs"
+      Link="STATestMethodAttribute.cs" />
   </ItemGroup>
+
   <ItemGroup>
-    <Content Include="HelperFiles\file1.svg">
+    <Content Include="HelperFiles\*.svg">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </Content>
-    <Content Include="HelperFiles\file2.svg">
+    <Content Include="HelperFiles\*.bmp">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </Content>
   </ItemGroup>
+
 </Project>

src/modules/previewpane/UnitTests-SvgThumbnailProvider/UnitTests-SvgThumbnailProvider.csproj

@@ -119,7 +119,7 @@ private static int FindFirstXmlOpenTagIndex(string s)
 
             while ((index = s.IndexOf('<', index)) != -1)
             {
-                if (index < s.Length - 1 && s[index + 1] != '?')
+                if (index < s.Length - 1 && s[index + 1] != '?' && s[index + 1] != '!')
                 {
                     return index;
                 }
@@ -130,11 +130,11 @@ private static int FindFirstXmlOpenTagIndex(string s)
             return -1;
         }
 
-        private static int FindFirstXmlCloseTagIndex(string s)
+        private static int FindFirstXmlCloseTagIndex(string s, int openTagIndex)
         {
             int index = 1;
 
-            while ((index = s.IndexOf('>', index)) != -1)
+            while ((index = s.IndexOf('>', openTagIndex)) != -1)
             {
                 if (index > 0 && s[index - 1] != '?')
                 {
@@ -160,7 +160,7 @@ public static string AddStyleSVG(string stringSvgData)
                 return stringSvgData;
             }
 
-            int firstXmlCloseTagIndex = FindFirstXmlCloseTagIndex(stringSvgData);
+            int firstXmlCloseTagIndex = FindFirstXmlCloseTagIndex(stringSvgData, firstXmlOpenTagIndex);
             if (firstXmlCloseTagIndex == -1)
             {
                 return stringSvgData;
@@ -192,13 +192,18 @@ public static string AddStyleSVG(string stringSvgData)
                 styleIndex -= numRemoved;
             }
 
+            firstXmlCloseTagIndex -= numRemoved;
+
             stringSvgData = RemoveAttribute(stringSvgData, heightIndex, HeightAttribute, out numRemoved);
             if (styleIndex != -1 && styleIndex > heightIndex)
             {
                 styleIndex -= numRemoved;
             }
 
+            firstXmlCloseTagIndex -= numRemoved;
+
             stringSvgData = RemoveAttribute(stringSvgData, styleIndex, StyleAttribute, out numRemoved);
+            firstXmlCloseTagIndex -= numRemoved;
 
             width = CheckUnit(width);
             height = CheckUnit(height);
@@ -213,7 +218,7 @@ public static string AddStyleSVG(string stringSvgData)
             scaling += $"  _height:expression(this.scrollHeight &gt; {heightR} ? &quot; {height}&quot; : &quot;auto&quot;); _width:expression(this.scrollWidth &gt; {widthR} ? &quot;{width}&quot; : &quot;auto&quot;);";
 
             string newStyle = $"style=\"{scaling}{centering}{oldStyle}\"";
-            int insertAt = stringSvgData.IndexOf(">", StringComparison.InvariantCultureIgnoreCase);
+            int insertAt = firstXmlCloseTagIndex;
 
             stringSvgData = stringSvgData.Insert(insertAt, " " + newStyle);