LibGL: Implement glDrawElements

Userland/Libraries/LibGL/GL/gl.h

@@ -362,6 +362,7 @@ GLAPI void glVertexPointer(GLint size, GLenum type, GLsizei stride, const void*
 GLAPI void glColorPointer(GLint size, GLenum type, GLsizei stride, const void* pointer);
 GLAPI void glTexCoordPointer(GLint size, GLenum type, GLsizei stride, const void* pointer);
 GLAPI void glDrawArrays(GLenum mode, GLint first, GLsizei count);
+GLAPI void glDrawElements(GLenum mode, GLsizei count, GLenum type, const void* indices);
 
 #ifdef __cplusplus
 }

Userland/Libraries/LibGL/GLContext.h

@@ -70,6 +70,7 @@ public:
     virtual void gl_color_pointer(GLint size, GLenum type, GLsizei stride, const void* pointer) = 0;
     virtual void gl_tex_coord_pointer(GLint size, GLenum type, GLsizei stride, const void* pointer) = 0;
     virtual void gl_draw_arrays(GLenum mode, GLint first, GLsizei count) = 0;
+    virtual void gl_draw_elements(GLenum mode, GLsizei count, GLenum type, const void* indices) = 0;
 
     virtual void present() = 0;
 };

Userland/Libraries/LibGL/GLVertexArrays.cpp

@@ -28,3 +28,8 @@ void glDrawArrays(GLenum mode, GLint first, GLsizei count)
 {
     g_gl_context->gl_draw_arrays(mode, first, count);
 }
+
+void glDrawElements(GLenum mode, GLsizei count, GLenum type, const void* indices)
+{
+    g_gl_context->gl_draw_elements(mode, count, type, indices);
+}

Userland/Libraries/LibGL/SoftwareGLContext.cpp

@@ -1542,6 +1542,64 @@ void SoftwareGLContext::gl_draw_arrays(GLenum mode, GLint first, GLsizei count)
     glEnd();
 }
 
+void SoftwareGLContext::gl_draw_elements(GLenum mode, GLsizei count, GLenum type, const void* indices)
+{
+    APPEND_TO_CALL_LIST_AND_RETURN_IF_NEEDED(gl_draw_elements, mode, count, type, indices);
+    RETURN_WITH_ERROR_IF(m_in_draw_state, GL_INVALID_OPERATION);
+
+    // FIXME: Some modes are still missing (GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES,GL_QUAD_STRIP)
+    RETURN_WITH_ERROR_IF(!(mode == GL_TRIANGLE_STRIP
+                             || mode == GL_TRIANGLE_FAN
+                             || mode == GL_TRIANGLES
+                             || mode == GL_QUADS
+                             || mode == GL_POLYGON),
+        GL_INVALID_ENUM);
+
+    RETURN_WITH_ERROR_IF(!(type == GL_UNSIGNED_BYTE
+                             || type == GL_UNSIGNED_SHORT
+                             || type == GL_UNSIGNED_INT),
+        GL_INVALID_ENUM);
+
+    RETURN_WITH_ERROR_IF(count < 0, GL_INVALID_VALUE);
+
+    // At least the vertex array needs to be enabled
+    if (!m_client_side_vertex_array_enabled)
+        return;
+
+    glBegin(mode);
+    for (int index = 0; index < count; index++) {
+        int i = 0;
+        switch (type) {
+        case GL_UNSIGNED_BYTE:
+            i = reinterpret_cast<const GLubyte*>(indices)[index];
+            break;
+        case GL_UNSIGNED_SHORT:
+            i = reinterpret_cast<const GLushort*>(indices)[index];
+            break;
+        case GL_UNSIGNED_INT:
+            i = reinterpret_cast<const GLuint*>(indices)[index];
+            break;
+        }
+
+        if (m_client_side_texture_coord_array_enabled) {
+            float tex_coords[4] { 0, 0, 0, 0 };
+            read_from_vertex_attribute_pointer(m_client_tex_coord_pointer, i, tex_coords, false);
+            glTexCoord4fv(tex_coords);
+        }
+
+        if (m_client_side_color_array_enabled) {
+            float color[4] { 0, 0, 0, 1 };
+            read_from_vertex_attribute_pointer(m_client_color_pointer, i, color, true);
+            glColor4fv(color);
+        }
+
+        float vertex[4] { 0, 0, 0, 1 };
+        read_from_vertex_attribute_pointer(m_client_vertex_pointer, i, vertex, false);
+        glVertex4fv(vertex);
+    }
+    glEnd();
+}
+
 // 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

@@ -80,6 +80,7 @@ public:
     virtual void gl_color_pointer(GLint size, GLenum type, GLsizei stride, const void* pointer) override;
     virtual void gl_tex_coord_pointer(GLint size, GLenum type, GLsizei stride, const void* pointer) override;
     virtual void gl_draw_arrays(GLenum mode, GLint first, GLsizei count) override;
+    virtual void gl_draw_elements(GLenum mode, GLsizei count, GLenum type, const void* indices) override;
 
     virtual void present() override;
 
@@ -210,7 +211,8 @@ private:
             decltype(&SoftwareGLContext::gl_read_buffer),
             decltype(&SoftwareGLContext::gl_tex_parameter),
             decltype(&SoftwareGLContext::gl_depth_mask),
-            decltype(&SoftwareGLContext::gl_draw_arrays)>;
+            decltype(&SoftwareGLContext::gl_draw_arrays),
+            decltype(&SoftwareGLContext::gl_draw_elements)>;
 
         using ExtraSavedArguments = Variant<
             FloatMatrix4x4>;