Add both long and short sampler names for random textures.

If a preset uses different long-form samplers for a single random slot, this will result in a failure, e.g. using both "sampler_rand00_something" and "sampler_rand00_else". As this also isn't supported by Milkdrop and would create a conflict situation, we don't care.

src/libprojectM/MilkdropPreset/MilkdropShader.cpp

@@ -517,6 +517,33 @@ void MilkdropShader::GetReferencedSamplers(const std::string& program)
         found = program.find("texsize_", found);
     }
 
+    {
+        // Remove duplicate mentions or "randXX" names, keeping the long forms only (first one will determine the actual texture loaded).
+        auto samplerName = m_samplerNames.begin();
+        std::locale loc;
+        while (samplerName != m_samplerNames.end())
+        {
+            std::string lowerCaseName = Utils::ToLower(*samplerName);
+            if (lowerCaseName.length() == 6 &&
+                lowerCaseName.substr(0, 4) == "rand" && std::isdigit(lowerCaseName.at(4), loc) && std::isdigit(lowerCaseName.at(5), loc))
+            {
+                auto additionalName = samplerName;
+                additionalName++;
+                if (additionalName != m_samplerNames.end())
+                {
+                    std::string addLowerCaseName = Utils::ToLower(*additionalName);
+                    if (addLowerCaseName.length() > 7 &&
+                        addLowerCaseName.substr(0, 6) == lowerCaseName &&
+                        addLowerCaseName[6] == '_')
+                    {
+                        samplerName = m_samplerNames.erase(samplerName);
+                    }
+                }
+            }
+            samplerName++;
+        }
+    }
+
     if (program.find("GetBlur3") != std::string::npos)
     {
         UpdateMaxBlurLevel(BlurTexture::BlurLevel::Blur3);

src/libprojectM/Renderer/TextureSamplerDescriptor.cpp

@@ -95,6 +95,15 @@ auto TextureSamplerDescriptor::SamplerDeclaration() const -> std::string
     declaration.append(m_samplerName);
     declaration.append(";\n");
 
+    // Add short sampler name for prefixed random textures.
+    // E.g. "sampler_rand00" if a sampler "sampler_rand00_smalltiled" was declared
+    if (m_samplerName.substr(0, 4) == "rand" && m_samplerName.length() > 7 && m_samplerName.at(6) == '_')
+    {
+        declaration.append("uniform sampler2D sampler_");
+        declaration.append(m_samplerName.substr(0, 6));
+        declaration.append(";\n");
+    }
+
     return declaration;
 }