LibGL: Implement glLightf{v} and fix gl.h prototype

This implements the `glLightf{v}` family of functions used to set
lighting parameters per light in the GL. It also fixes an incorrect
prototype for the user exposed version of `glLightf{v}` in which
`params` was not marked as `const`.

Userland/Libraries/LibSoftGPU/Device.cpp

@@ -1004,4 +1004,9 @@ void Device::set_sampler_config(unsigned sampler, SamplerConfig const& config)
     m_samplers[sampler].set_config(config);
 }
 
+void Device::set_light_state(unsigned int light_id, Light const& light)
+{
+    m_lights.at(light_id) = light;
+}
+
 }

Userland/Libraries/LibSoftGPU/Device.h

@@ -22,6 +22,7 @@
 #include <LibSoftGPU/Enums.h>
 #include <LibSoftGPU/Image.h>
 #include <LibSoftGPU/ImageFormat.h>
+#include <LibSoftGPU/Light/Light.h>
 #include <LibSoftGPU/Sampler.h>
 #include <LibSoftGPU/Triangle.h>
 #include <LibSoftGPU/Vertex.h>
@@ -92,6 +93,7 @@ public:
     NonnullRefPtr<Image> create_image(ImageFormat, unsigned width, unsigned height, unsigned depth, unsigned levels, unsigned layers);
 
     void set_sampler_config(unsigned, SamplerConfig const&);
+    void set_light_state(unsigned, Light const&);
 
 private:
     void draw_statistics_overlay(Gfx::Bitmap&);
@@ -112,6 +114,7 @@ private:
     Array<Sampler, NUM_SAMPLERS> m_samplers;
     Vector<size_t> m_enabled_texture_units;
     AlphaBlendFactors m_alpha_blend_factors;
+    Array<Light, NUM_LIGHTS> m_lights;
 };
 
 }

Userland/Libraries/LibSoftGPU/Light/Light.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2022, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGfx/Vector3.h>
+#include <LibGfx/Vector4.h>
+
+namespace SoftGPU {
+
+struct Light {
+    bool is_enabled { false };
+
+    // According to the OpenGL 1.5 specification, page 56, all of the parameters
+    // for the following data members (positions, colors, and reals) are all
+    // floating point.
+    Vector4<float> ambient_intensity { 0.0f, 0.0f, 0.0f, 1.0f };
+    Vector4<float> diffuse_intensity { 0.0f, 0.0f, 0.0f, 1.0f };
+    Vector4<float> specular_intensity { 0.0f, 0.0f, 0.0f, 1.0f };
+    Vector4<float> position { 0.0f, 0.0f, 1.0f, 0.0f };
+    Vector3<float> spotlight_direction { 0.0f, 0.0f, -1.0f };
+
+    float spotlight_exponent { 0.0f };
+    float spotlight_cutoff_angle { 180.0f };
+    float constant_attenuation { 1.0f };  // This is referred to `k0i` in the OpenGL spec
+    float linear_attenuation { 0.0f };    // This is referred to `k1i` in the OpenGL spec
+    float quadratic_attenuation { 0.0f }; // This is referred to `k2i` in the OpenGL spec
+
+    float spotlight_cutoff_angle_rads { AK::Pi<float> / 180.0f };
+};
+
+}