LibGL: Implement glDepthFunc

Userland/Libraries/LibGL/GL/gl.h

@@ -370,6 +370,7 @@ GLAPI void glTexCoordPointer(GLint size, GLenum type, GLsizei stride, const void
 GLAPI void glDrawArrays(GLenum mode, GLint first, GLsizei count);
 GLAPI void glDrawElements(GLenum mode, GLsizei count, GLenum type, const void* indices);
 GLAPI void glDepthRange(GLdouble nearVal, GLdouble farVal);
+GLAPI void glDepthFunc(GLenum func);
 
 #ifdef __cplusplus
 }

Userland/Libraries/LibGL/GLContext.h

@@ -75,6 +75,7 @@ public:
     virtual void gl_get_booleanv(GLenum pname, GLboolean* data) = 0;
     virtual void gl_get_integerv(GLenum pname, GLint* data) = 0;
     virtual void gl_depth_range(GLdouble min, GLdouble max) = 0;
+    virtual void gl_depth_func(GLenum func) = 0;
 
     virtual void present() = 0;
 };

Userland/Libraries/LibGL/GLUtils.cpp

@@ -124,3 +124,8 @@ void glDepthRange(GLdouble min, GLdouble max)
 {
     g_gl_context->gl_depth_range(min, max);
 }
+
+void glDepthFunc(GLenum func)
+{
+    g_gl_context->gl_depth_func(func);
+}

Userland/Libraries/LibGL/SoftwareGLContext.cpp

@@ -1653,6 +1653,27 @@ void SoftwareGLContext::gl_depth_range(GLdouble min, GLdouble max)
     m_rasterizer.set_options(options);
 }
 
+void SoftwareGLContext::gl_depth_func(GLenum func)
+{
+    APPEND_TO_CALL_LIST_AND_RETURN_IF_NEEDED(gl_depth_func, func);
+
+    RETURN_WITH_ERROR_IF(m_in_draw_state, GL_INVALID_OPERATION);
+
+    RETURN_WITH_ERROR_IF(!(func == GL_NEVER
+                             || func == GL_LESS
+                             || func == GL_EQUAL
+                             || func == GL_LEQUAL
+                             || func == GL_GREATER
+                             || func == GL_NOTEQUAL
+                             || func == GL_GEQUAL
+                             || func == GL_ALWAYS),
+        GL_INVALID_ENUM);
+
+    auto options = m_rasterizer.options();
+    options.depth_func = func;
+    m_rasterizer.set_options(options);
+}
+
 // General helper function to read arbitrary vertex attribute data into a float array
 void SoftwareGLContext::read_from_vertex_attribute_pointer(VertexAttribPointer const& attrib, int index, float* elements, bool normalize)
 {

Userland/Libraries/LibGL/SoftwareGLContext.h

@@ -85,6 +85,7 @@ public:
     virtual void gl_get_booleanv(GLenum pname, GLboolean* data) override;
     virtual void gl_get_integerv(GLenum pname, GLint* data) override;
     virtual void gl_depth_range(GLdouble min, GLdouble max) override;
+    virtual void gl_depth_func(GLenum func) override;
     virtual void present() override;
 
 private:

Userland/Libraries/LibGL/SoftwareRasterizer.cpp

@@ -261,8 +261,36 @@ static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& re
                         auto barycentric = FloatVector3(coords.x(), coords.y(), coords.z()) * one_over_area;
                         float z = interpolate(triangle.vertices[0].z, triangle.vertices[1].z, triangle.vertices[2].z, barycentric);
                         z = options.depth_min + (options.depth_max - options.depth_min) * (z + 1) / 2;
-                        
-                        if (z >= *depth) {
+
+                        bool pass = false;
+                        switch (options.depth_func) {
+                        case GL_ALWAYS:
+                            pass = true;
+                            break;
+                        case GL_NEVER:
+                            pass = false;
+                            break;
+                        case GL_GREATER:
+                            pass = z > *depth;
+                            break;
+                        case GL_GEQUAL:
+                            pass = z >= *depth;
+                            break;
+                        case GL_NOTEQUAL:
+                            pass = z != *depth;
+                            break;
+                        case GL_EQUAL:
+                            pass = z == *depth;
+                            break;
+                        case GL_LEQUAL:
+                            pass = z <= *depth;
+                            break;
+                        case GL_LESS:
+                            pass = z < *depth;
+                            break;
+                        }
+
+                        if (!pass) {
                             pixel_mask[y] ^= 1 << x;
                             continue;
                         }

Userland/Libraries/LibGL/SoftwareRasterizer.h

@@ -31,6 +31,7 @@ struct RasterizerOptions {
     u32 color_mask { 0xffffffff };
     float depth_min { 0 };
     float depth_max { 1 };
+    GLenum depth_func { GL_LESS };
 };
 
 class SoftwareRasterizer final {