Fix: MilkdropShader - ignore sampler keywords in shader comments (#958)

Author: mbaetgen-wup

src/libprojectM/MilkdropPreset/MilkdropShader.cpp

@@ -341,32 +341,36 @@ void MilkdropShader::PreprocessPresetShader(std::string& program)
 
     // Find "sampler_state" overrides and remove them first, as they're not supported by GLSL.
     // The logic isn't totally fool-proof, but should work in general.
-    found = program.find("sampler_state");
+    // Use a comment-stripped copy for searching so commented-out sampler_state blocks are skipped.
+    // StripComments preserves string length, so positions map 1:1 to the original.
+    std::string stripped = Utils::StripComments(program);
+    found = stripped.find("sampler_state");
     while (found != std::string::npos)
     {
         // Now go backwards and find the assignment
-        found = program.rfind('=', found);
+        found = stripped.rfind('=', found);
         auto startPos = found;
 
         // Find closing brace and semicolon
-        found = program.find('}', found);
-        found = program.find(';', found);
+        found = stripped.find('}', found);
+        found = stripped.find(';', found);
 
         if (found != std::string::npos)
         {
-            program.replace(startPos, found - startPos, "");
+            stripped.replace(startPos, found - startPos, "");
         }
         else
         {
             // No closing brace and semicolon.
             break;
         }
 
-        found = program.find("sampler_state");
+        found = stripped.find("sampler_state");
     }
 
     // replace shader_body with entry point function
-    found = program.find("shader_body");
+    // Use the stripped copy so a commented-out shader_body is not matched.
+    found = stripped.find("shader_body");
     if (found != std::string::npos)
     {
         if (m_type == ShaderType::WarpShader)
@@ -430,7 +434,7 @@ void PS(float4 _vDiffuse : COLOR,
         switch (program.at(pos))
         {
             case '/':
-                // Skip comments until EoL to prevent false counting
+                // Skip line comments until EoL to prevent false counting
                 if (pos < program.length() - 1 && program.at(pos + 1) == '/')
                 {
                     for (; pos < program.length(); ++pos)
@@ -441,6 +445,19 @@ void PS(float4 _vDiffuse : COLOR,
                         }
                     }
                 }
+                // Skip block comments to prevent false counting
+                else if (pos < program.length() - 1 && program.at(pos + 1) == '*')
+                {
+                    pos += 2;
+                    for (; pos < program.length() - 1; ++pos)
+                    {
+                        if (program.at(pos) == '*' && program.at(pos + 1) == '/')
+                        {
+                            ++pos; // skip past '/'
+                            break;
+                        }
+                    }
+                }
                 continue;
 
             case '{':
@@ -492,40 +509,43 @@ void MilkdropShader::GetReferencedSamplers(const std::string& program)
     // "main" should always be present.
     m_samplerNames.insert("main");
 
+    // Strip comments so that commented-out sampler/texsize declarations are not matched.
+    std::string const stripped = Utils::StripComments(program);
+
     // Search for sampler usage
-    auto found = program.find("sampler_", 0);
+    auto found = stripped.find("sampler_", 0);
     while (found != std::string::npos)
     {
         found += 8;
-        size_t const end = program.find_first_of(" ;,\n\r)", found);
+        size_t const end = stripped.find_first_of(" ;,\n\r)", found);
 
         if (end != std::string::npos)
         {
-            std::string const sampler = program.substr(static_cast<int>(found), static_cast<int>(end - found));
+            std::string const sampler = stripped.substr(static_cast<int>(found), static_cast<int>(end - found));
             // Skip "sampler_state", as it's a reserved word and not a sampler.
             if (sampler != "state")
             {
                 m_samplerNames.insert(sampler);
             }
         }
 
-        found = program.find("sampler_", found);
+        found = stripped.find("sampler_", found);
     }
 
     // Also search for texsize usage, some presets don't reference the sampler.
-    found = program.find("texsize_", 0);
+    found = stripped.find("texsize_", 0);
     while (found != std::string::npos)
     {
         found += 8;
-        size_t const end = program.find_first_of(" ;,.\n\r)", found);
+        size_t const end = stripped.find_first_of(" ;,.\n\r)", found);
 
         if (end != std::string::npos)
         {
-            std::string const sampler = program.substr(static_cast<int>(found), static_cast<int>(end - found));
+            std::string const sampler = stripped.substr(static_cast<int>(found), static_cast<int>(end - found));
             m_samplerNames.insert(sampler);
         }
 
-        found = program.find("texsize_", found);
+        found = stripped.find("texsize_", found);
     }
 
     {
@@ -555,15 +575,15 @@ void MilkdropShader::GetReferencedSamplers(const std::string& program)
         }
     }
 
-    if (program.find("GetBlur3") != std::string::npos)
+    if (stripped.find("GetBlur3") != std::string::npos)
     {
         UpdateMaxBlurLevel(BlurTexture::BlurLevel::Blur3);
     }
-    else if (program.find("GetBlur2") != std::string::npos)
+    else if (stripped.find("GetBlur2") != std::string::npos)
     {
         UpdateMaxBlurLevel(BlurTexture::BlurLevel::Blur2);
     }
-    else if (program.find("GetBlur1") != std::string::npos)
+    else if (stripped.find("GetBlur1") != std::string::npos)
     {
         UpdateMaxBlurLevel(BlurTexture::BlurLevel::Blur1);
     }

src/libprojectM/Utils.cpp

@@ -29,5 +29,53 @@ void ToUpperInPlace(std::string& str)
     std::transform(str.begin(), str.end(), str.begin(), ::toupper);
 }
 
+auto StripComments(const std::string& source) -> std::string
+{
+    std::string result = source;
+    size_t i = 0;
+
+    while (i < result.size())
+    {
+        if (i + 1 < result.size() && result.at(i) == '/' && result.at(i + 1) == '/')
+        {
+            // Line comment: replace until end of line
+            while (i < result.size() && result.at(i) != '\n' && result.at(i) != '\r')
+            {
+                result.at(i) = ' ';
+                i++;
+            }
+        }
+        else if (i + 1 < result.size() && result.at(i) == '/' && result.at(i + 1) == '*')
+        {
+            // Block comment: replace until closing */
+            result.at(i) = ' ';
+            result.at(i + 1) = ' ';
+            i += 2;
+            while (i < result.size())
+            {
+                if (i + 1 < result.size() && result.at(i) == '*' && result.at(i + 1) == '/')
+                {
+                    result.at(i) = ' ';
+                    result.at(i + 1) = ' ';
+                    i += 2;
+                    break;
+                }
+                // Preserve newlines to keep line structure intact
+                if (result.at(i) != '\n' && result.at(i) != '\r')
+                {
+                    result.at(i) = ' ';
+                }
+                i++;
+            }
+        }
+        else
+        {
+            i++;
+        }
+    }
+
+    return result;
+}
+
 } // namespace Utils
 } // namespace libprojectM

src/libprojectM/Utils.hpp

@@ -11,5 +11,16 @@ auto ToUpper(const std::string& str) -> std::string;
 void ToLowerInPlace(std::string& str);
 void ToUpperInPlace(std::string& str);
 
+/**
+ * @brief Strips C and C++ style comments from source code.
+ *
+ * Replaces // line comments and block comments with spaces, preserving
+ * string length and newline positions so that character offsets remain valid.
+ *
+ * @param source The source code string to strip comments from.
+ * @return A copy of the source with all comment content replaced by spaces.
+ */
+auto StripComments(const std::string& source) -> std::string;
+
 } // namespace Utils
 } // namespace libprojectM

tests/libprojectM/CMakeLists.txt

@@ -3,6 +3,7 @@ find_package(GTest 1.10 REQUIRED NO_MODULE)
 add_executable(projectM-unittest
         WaveformAlignerTest.cpp
         PresetFileParserTest.cpp
+        MilkdropShaderCommentParsingTest.cpp
 
         $<TARGET_OBJECTS:Audio>
         $<TARGET_OBJECTS:MilkdropPreset>