LibGL+LibWeb: Remove WebGL-specific API from GLContext

The OpenGL API has ways to retrieve these values, so let's make sure to
implement them. :^)

Author: gmta

Tests/LibGL/TestAPI.cpp

@@ -61,3 +61,51 @@ TEST_CASE(0003_gl_bind_buffer_names_must_be_allocated)
     glBindBuffer(GL_ARRAY_BUFFER, 123);
     EXPECT_EQ(glGetError(), static_cast<GLenum>(GL_INVALID_VALUE));
 }
+
+TEST_CASE(0004_gl_color_clear_value)
+{
+    auto context = create_testing_context();
+
+    Array<GLdouble, 4> clear_color;
+    glGetDoublev(GL_COLOR_CLEAR_VALUE, clear_color.data());
+    EXPECT_EQ(clear_color[0], 0.);
+    EXPECT_EQ(clear_color[1], 0.);
+    EXPECT_EQ(clear_color[2], 0.);
+    EXPECT_EQ(clear_color[3], 0.);
+
+    glClearColor(.1f, .2f, .3f, .4f);
+
+    glGetDoublev(GL_COLOR_CLEAR_VALUE, clear_color.data());
+    EXPECT_APPROXIMATE(clear_color[0], .1);
+    EXPECT_APPROXIMATE(clear_color[1], .2);
+    EXPECT_APPROXIMATE(clear_color[2], .3);
+    EXPECT_APPROXIMATE(clear_color[3], .4);
+}
+
+TEST_CASE(0005_gl_depth_clear_value)
+{
+    auto context = create_testing_context();
+
+    GLdouble clear_depth;
+    glGetDoublev(GL_DEPTH_CLEAR_VALUE, &clear_depth);
+    EXPECT_EQ(clear_depth, 1.);
+
+    glClearDepth(.1f);
+
+    glGetDoublev(GL_DEPTH_CLEAR_VALUE, &clear_depth);
+    EXPECT_APPROXIMATE(clear_depth, .1);
+}
+
+TEST_CASE(0006_gl_stencil_clear_value)
+{
+    auto context = create_testing_context();
+
+    GLint clear_stencil;
+    glGetIntegerv(GL_STENCIL_CLEAR_VALUE, &clear_stencil);
+    EXPECT_EQ(clear_stencil, 0);
+
+    glClearStencil(255);
+
+    glGetIntegerv(GL_STENCIL_CLEAR_VALUE, &clear_stencil);
+    EXPECT_EQ(clear_stencil, 255);
+}

Userland/Libraries/LibGL/ContextParameter.cpp

@@ -30,6 +30,18 @@ Optional<ContextParameter> GLContext::get_context_parameter(GLenum name)
         return ContextParameter { .type = GL_INT, .value = { .integer_value = sizeof(u8) * 8 } };
     case GL_CLIENT_ACTIVE_TEXTURE:
         return ContextParameter { .type = GL_INT, .value = { .integer_value = static_cast<GLint>(GL_TEXTURE0 + m_client_active_texture) } };
+    case GL_COLOR_CLEAR_VALUE:
+        return ContextParameter {
+            .type = GL_DOUBLE,
+            .count = 4,
+            .value = {
+                .double_list = {
+                    static_cast<GLdouble>(m_clear_color.x()),
+                    static_cast<GLdouble>(m_clear_color.y()),
+                    static_cast<GLdouble>(m_clear_color.z()),
+                    static_cast<GLdouble>(m_clear_color.w()),
+                } }
+        };
     case GL_COLOR_MATERIAL:
         return ContextParameter { .type = GL_BOOL, .is_capability = true, .value = { .boolean_value = m_color_material_enabled } };
     case GL_COLOR_MATERIAL_FACE:
@@ -52,6 +64,8 @@ Optional<ContextParameter> GLContext::get_context_parameter(GLenum name)
         return ContextParameter { .type = GL_BOOL, .is_capability = true, .value = { .boolean_value = m_cull_faces } };
     case GL_DEPTH_BITS:
         return ContextParameter { .type = GL_INT, .value = { .integer_value = sizeof(float) * 8 } };
+    case GL_DEPTH_CLEAR_VALUE:
+        return ContextParameter { .type = GL_DOUBLE, .value = { .double_value = static_cast<GLdouble>(m_clear_depth) } };
     case GL_DEPTH_TEST:
         return ContextParameter { .type = GL_BOOL, .is_capability = true, .value = { .boolean_value = m_depth_test_enabled } };
     case GL_DITHER:

Userland/Libraries/LibGL/GL/gl.h

@@ -103,10 +103,12 @@ extern "C" {
 #define GL_COLOR_MATERIAL 0x0B57
 #define GL_FOG_START 0x0B63
 #define GL_FOG_END 0x0B64
+#define GL_DEPTH_CLEAR_VALUE 0x0B73
 #define GL_STENCIL_CLEAR_VALUE 0x0B91
 #define GL_MATRIX_MODE 0x0BA0
 #define GL_NORMALIZE 0x0BA1
 #define GL_VIEWPORT 0x0BA2
+#define GL_COLOR_CLEAR_VALUE 0x0C22
 #define GL_DOUBLEBUFFER 0x0C32
 #define GL_TEXTURE_GEN_S 0x0C60
 #define GL_TEXTURE_GEN_T 0x0C61

Userland/Libraries/LibGL/GLContext.h

@@ -107,12 +107,6 @@ class GLContext final {
     NonnullRefPtr<Gfx::Bitmap> frontbuffer() const { return m_frontbuffer; };
     void present();
 
-    // Used by WebGL to preserve the clear values when implicitly clearing the front buffer.
-    // FIXME: Add ContextParameters for these and expose them through methods such as gl_get_floatv instead of having a public API like this.
-    FloatVector4 current_clear_color() const { return m_clear_color; }
-    GLdouble current_clear_depth() const { return m_clear_depth; }
-    GLint current_clear_stencil() const { return m_clear_stencil; }
-
     void gl_begin(GLenum mode);
     void gl_clear(GLbitfield mask);
     void gl_clear_color(GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha);

Userland/Libraries/LibWeb/WebGL/WebGLRenderingContextBase.cpp

@@ -52,9 +52,14 @@ void WebGLRenderingContextBase::present()
     // This default behavior can be changed by setting the preserveDrawingBuffer attribute of the WebGLContextAttributes object.
     // If this flag is true, the contents of the drawing buffer shall be preserved until the author either clears or overwrites them."
     if (!m_context_creation_parameters.preserve_drawing_buffer) {
-        auto current_clear_color = m_context->current_clear_color();
-        auto current_clear_depth = m_context->current_clear_depth();
-        auto current_clear_stencil = m_context->current_clear_stencil();
+        Array<GLdouble, 4> current_clear_color;
+        m_context->gl_get_doublev(GL_COLOR_CLEAR_VALUE, current_clear_color.data());
+
+        GLdouble current_clear_depth;
+        m_context->gl_get_doublev(GL_DEPTH_CLEAR_VALUE, &current_clear_depth);
+
+        GLint current_clear_stencil;
+        m_context->gl_get_integerv(GL_STENCIL_CLEAR_VALUE, &current_clear_stencil);
 
         // The implicit clear value for the color buffer is (0, 0, 0, 0)
         m_context->gl_clear_color(0, 0, 0, 0);