LibGL: Implement `glLightModel` integer normalization

For the ambient light model, integers need to be remapped to a range of
`-1.` through `1.`. Add the `+` and `-` operators to `VectorN` to make
it a bit easier to normalize 4 values at once.

2 files changed, 36 insertions, 19 deletions

diff --git a/Userland/Libraries/LibGL/Lighting.cpp b/Userland/Libraries/LibGL/Lighting.cpp
index 222e28baa5..2e5409d9d0 100644
--- a/Userland/Libraries/LibGL/Lighting.cpp
+++ b/Userland/Libraries/LibGL/Lighting.cpp
@@ -193,26 +193,23 @@ void GLContext::gl_light_model(GLenum pname, GLfloat x, GLfloat y, GLfloat z, GL
 
 void GLContext::gl_light_modelv(GLenum pname, void const* params, GLenum type)
 {
-    auto invoke_implementation = [&](auto const* params) {
-        switch (pname) {
-        case GL_LIGHT_MODEL_AMBIENT:
-            gl_light_model(pname, params[0], params[1], params[2], params[3]);
-            return;
-        default:
-            gl_light_model(pname, params[0], 0.f, 0.f, 0.f);
-            return;
-        }
+    VERIFY(type == GL_FLOAT || type == GL_INT);
+
+    auto parameters_to_vector = [&]<typename T>(T const* params) -> FloatVector4 {
+        return (pname == GL_LIGHT_MODEL_AMBIENT)
+            ? Vector4<T> { params[0], params[1], params[2], params[3] }.template to_type<float>()
+            : Vector4<T> { params[0], 0, 0, 0 }.template to_type<float>();
     };
-    switch (type) {
-    case GL_FLOAT:
-        invoke_implementation(reinterpret_cast<GLfloat const*>(params));
-        break;
-    case GL_INT:
-        invoke_implementation(reinterpret_cast<GLint const*>(params));
-        break;
-    default:
-        VERIFY_NOT_REACHED();
-    }
+
+    auto light_model_parameters = (type == GL_FLOAT)
+        ? parameters_to_vector(reinterpret_cast<GLfloat const*>(params))
+        : parameters_to_vector(reinterpret_cast<GLint const*>(params));
+
+    // Normalize integers to -1..1
+    if (pname == GL_LIGHT_MODEL_AMBIENT && type == GL_INT)
+        light_model_parameters = (light_model_parameters + 2147483648.f) / 2147483647.5f - 1.f;
+
+    gl_light_model(pname, light_model_parameters[0], light_model_parameters[1], light_model_parameters[2], light_model_parameters[3]);
 }
 
 void GLContext::gl_lightf(GLenum light, GLenum pname, GLfloat param)
diff --git a/Userland/Libraries/LibGfx/VectorN.h b/Userland/Libraries/LibGfx/VectorN.h
index 7e67a72695..687c0ea7df 100644
--- a/Userland/Libraries/LibGfx/VectorN.h
+++ b/Userland/Libraries/LibGfx/VectorN.h
@@ -159,6 +159,26 @@ public:
     }
 
     template<typename U>
+    [[nodiscard]] constexpr VectorN operator+(U f) const
+    {
+        VectorN result;
+        UNROLL_LOOP
+        for (auto i = 0u; i < N; ++i)
+            result.m_data[i] = m_data[i] + f;
+        return result;
+    }
+
+    template<typename U>
+    [[nodiscard]] constexpr VectorN operator-(U f) const
+    {
+        VectorN result;
+        UNROLL_LOOP
+        for (auto i = 0u; i < N; ++i)
+            result.m_data[i] = m_data[i] - f;
+        return result;
+    }
+
+    template<typename U>
     [[nodiscard]] constexpr VectorN operator*(U f) const
     {
         VectorN result;