LibSoftGPU: Remove OpenGL type for fog mode

Replaces the GLenum used to set up the fog mode in RasterizerOptions
with out own enum.

Userland/Libraries/LibGL/SoftwareGLContext.cpp

@@ -2356,7 +2356,17 @@ void SoftwareGLContext::gl_fogi(GLenum pname, GLint param)
 
     switch (pname) {
     case GL_FOG_MODE:
-        options.fog_mode = param;
+        switch (param) {
+        case GL_LINEAR:
+            options.fog_mode = SoftGPU::FogMode::Linear;
+            break;
+        case GL_EXP:
+            options.fog_mode = SoftGPU::FogMode::Exp;
+            break;
+        case GL_EXP2:
+            options.fog_mode = SoftGPU::FogMode::Exp2;
+            break;
+        }
         break;
     default:
         RETURN_WITH_ERROR_IF(true, GL_INVALID_ENUM);

Userland/Libraries/LibSoftGPU/Device.cpp

@@ -687,13 +687,13 @@ void Device::submit_triangle(const Triangle& triangle, Vector<size_t> const& ena
         if (m_options.fog_enabled) {
             float factor = 0.0f;
             switch (m_options.fog_mode) {
-            case GL_LINEAR:
+            case FogMode::Linear:
                 factor = (m_options.fog_end - z) / (m_options.fog_end - m_options.fog_start);
                 break;
-            case GL_EXP:
+            case FogMode::Exp:
                 factor = exp(-((m_options.fog_density * z)));
                 break;
-            case GL_EXP2:
+            case FogMode::Exp2:
                 factor = exp(-((m_options.fog_density * z) * (m_options.fog_density * z)));
                 break;
             default:

Userland/Libraries/LibSoftGPU/Device.h

@@ -62,6 +62,12 @@ enum class DepthTestFunction {
     Greater,
 };
 
+enum FogMode {
+    Linear,
+    Exp,
+    Exp2
+};
+
 enum class WindingOrder {
     Clockwise,
     CounterClockwise,
@@ -84,7 +90,7 @@ struct RasterizerOptions {
     GLenum polygon_mode { GL_FILL };
     FloatVector4 fog_color { 0.0f, 0.0f, 0.0f, 0.0f };
     float fog_density { 1.0f };
-    GLenum fog_mode { GL_EXP };
+    FogMode fog_mode { FogMode::Exp };
     bool fog_enabled { false };
     float fog_start { 0.0f };
     float fog_end { 1.0f };