LibGL+LibSoftGPU: Implement texture coordinate generation

Texture coordinate generation is the concept of automatically
generating vertex texture coordinates instead of using the provided
coordinates (i.e. `glTexCoord`).

This commit implements support for:

* The `GL_TEXTURE_GEN_Q/R/S/T` capabilities
* The `GL_OBJECT_LINEAR`, `GL_EYE_LINEAR`, `GL_SPHERE_MAP`,
  `GL_REFLECTION_MAP` and `GL_NORMAL_MAP` modes
* Object and eye plane coefficients (write-only at the moment)

This changeset allows Tux Racer to render its terrain :^)

1 files changed, 37 insertions, 0 deletions

diff --git a/Userland/Libraries/LibGL/SoftwareGLContext.h b/Userland/Libraries/LibGL/SoftwareGLContext.h
index 1099525e50..e685710004 100644
--- a/Userland/Libraries/LibGL/SoftwareGLContext.h
+++ b/Userland/Libraries/LibGL/SoftwareGLContext.h
@@ -140,6 +140,7 @@ public:
 private:
     void sync_device_config();
     void sync_device_sampler_config();
+    void sync_device_texcoord_config();
 
 private:
     template<typename T>
@@ -243,6 +244,42 @@ private:
     Vector<TextureUnit, 32> m_texture_units;
     TextureUnit* m_active_texture_unit;
 
+    // Texture coordinate generation state
+    struct TextureCoordinateGeneration {
+        bool enabled { false };
+        GLenum generation_mode { GL_EYE_LINEAR };
+        FloatVector4 object_plane_coefficients;
+        FloatVector4 eye_plane_coefficients;
+    };
+    Array<TextureCoordinateGeneration, 4> m_texture_coordinate_generation {
+        // S
+        TextureCoordinateGeneration {
+            .object_plane_coefficients = { 1.0f, 0.0f, 0.0f, 0.0f },
+            .eye_plane_coefficients = { 1.0f, 0.0f, 0.0f, 0.0f },
+        },
+        // T
+        TextureCoordinateGeneration {
+            .object_plane_coefficients = { 0.0f, 1.0f, 0.0f, 0.0f },
+            .eye_plane_coefficients = { 0.0f, 1.0f, 0.0f, 0.0f },
+        },
+        // R
+        TextureCoordinateGeneration {
+            .object_plane_coefficients = { 0.0f, 0.0f, 0.0f, 0.0f },
+            .eye_plane_coefficients = { 0.0f, 0.0f, 0.0f, 0.0f },
+        },
+        // Q
+        TextureCoordinateGeneration {
+            .object_plane_coefficients = { 0.0f, 0.0f, 0.0f, 0.0f },
+            .eye_plane_coefficients = { 0.0f, 0.0f, 0.0f, 0.0f },
+        },
+    };
+    bool m_texcoord_generation_dirty { true };
+
+    ALWAYS_INLINE TextureCoordinateGeneration& texture_coordinate_generation(GLenum capability)
+    {
+        return m_texture_coordinate_generation[capability - GL_TEXTURE_GEN_S];
+    }
+
     SoftGPU::Device m_rasterizer;
     SoftGPU::DeviceInfo const m_device_info;
     bool m_sampler_config_is_dirty { true };