Fix bad material SSBO uniform layout for multiple of 16

If the uniform size is divisible by 16 it wrongly thought
that 16 bytes of padding (instead of 0) were needed.

Add a unit test demonstrating the case that was broken.

Author: slipher

CMakeLists.txt

@@ -952,7 +952,7 @@ if (BUILD_CLIENT)
         Flags ${WARNINGS}
         Files ${WIN_RC} ${BUILDINFOLIST} ${QCOMMONLIST} ${SERVERLIST} ${CLIENTBASELIST} ${CLIENTLIST}
         Libs ${LIBS_CLIENT} ${LIBS_CLIENTBASE} ${LIBS_ENGINE}
-        Tests ${ENGINETESTLIST}
+        Tests ${CLIENTTESTLIST}
     )
 
     # generate glsl include files

src.cmake

@@ -356,6 +356,10 @@ set(CLIENTLIST
     ${RENDERERLIST}
 )
 
+set(CLIENTTESTLIST ${ENGINETESTLIST}
+    ${ENGINE_DIR}/renderer/gl_shader_test.cpp
+)
+
 set(TTYCLIENTLIST
     ${ENGINE_DIR}/null/NullAudio.cpp
     ${ENGINE_DIR}/null/NullKeyboard.cpp

src/engine/renderer/gl_shader.cpp

@@ -2128,14 +2128,14 @@ void GLShader::PostProcessUniforms() {
 		GLuint size = _materialSystemUniforms[0]->_std430Size;
 		GLuint components = _materialSystemUniforms[0]->_components;
 		size = components ? PAD( size, 4 ) * components : size;
-		GLuint alignmentConsume = 4 - size % 4;
+		GLuint alignmentConsume = PAD( size, 4 ) - size;
 
 		GLUniform* tmpUniform = _materialSystemUniforms[0];
 		tmp.emplace_back( _materialSystemUniforms[0] );
 		_materialSystemUniforms.erase( _materialSystemUniforms.begin() );
 
 		int uniform;
-		while ( ( alignmentConsume & 3 ) && _materialSystemUniforms.size()
+		while ( alignmentConsume  && _materialSystemUniforms.size()
 			&& ( uniform = FindUniformForAlignment( _materialSystemUniforms, alignmentConsume ) ) != -1 ) {
 			alignmentConsume -= _materialSystemUniforms[uniform]->_std430Size;
 

src/engine/renderer/gl_shader_test.cpp

@@ -0,0 +1,76 @@
+/*
+===========================================================================
+Daemon BSD Source Code
+Copyright (c) 2025, Daemon Developers
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+    * Neither the name of the Daemon developers nor the
+      names of its contributors may be used to endorse or promote products
+      derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL DAEMON DEVELOPERS BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+===========================================================================
+*/
+
+#include <gtest/gtest.h>
+
+#include "common/Common.h"
+
+#include "engine/renderer/gl_shader.h"
+
+namespace {
+
+class MaterialUniformPackingTestShaderBase : public GLShader
+{
+public:
+    MaterialUniformPackingTestShaderBase()
+       : GLShader("MaterialUniformPackingTestShaderBase", 0, true, "", "") {}
+
+    std::vector<GLUniform*> GetUniforms()
+    {
+        PostProcessUniforms();
+        return _materialSystemUniforms;
+    }
+};
+
+template<typename U, typename ShaderT>
+GLUniform* Get(ShaderT& shader)
+{
+   // assume U has a single base class of GLUniform
+   return reinterpret_cast<GLUniform*>(static_cast<U*>(&shader));
+}
+
+TEST(MaterialUniformPackingTest, OneMatrix)
+{
+    class Shader1 : public MaterialUniformPackingTestShaderBase,
+                    public u_ModelViewMatrix //mat4
+    {
+    public:
+        Shader1() : u_ModelViewMatrix(this) {}
+    };
+
+    Shader1 shader1;
+    std::vector<GLUniform*> uniforms = shader1.GetUniforms();
+    EXPECT_EQ(shader1.GetSTD430Size(), 16u);
+    ASSERT_EQ(uniforms.size(), 1);
+    EXPECT_EQ(uniforms[0], Get<u_ModelViewMatrix>(shader1));
+    EXPECT_EQ(uniforms[0]->_std430Size, 16u);
+}
+
+} // namespace