LibGL: Add defines and stubs for glBlendFunc()

Userland/Libraries/LibGL/CMakeLists.txt

@@ -1,5 +1,6 @@
 set(SOURCES
     Clipper.cpp
+    GLBlend.cpp
     GLColor.cpp
     GLContext.cpp
     GLLists.cpp

Userland/Libraries/LibGL/GL/gl.h

@@ -42,6 +42,19 @@ extern "C" {
 #define GL_RENDERER 0x1F01
 #define GL_VERSION 0x1F02
 
+/* Blend factors */
+#define GL_ZERO 0
+#define GL_ONE 1
+#define GL_SRC_COLOR 0x0300
+#define GL_ONE_MINUS_SRC_COLOR 0x0301
+#define GL_SRC_ALPHA 0x0302
+#define GL_ONE_MINUS_SRC_ALPHA 0x0303
+#define GL_DST_ALPHA 0x0304
+#define GL_ONE_MINUS_DST_ALPHA 0x0305
+#define GL_DST_COLOR 0x0306
+#define GL_ONE_MINUS_DST_COLOR 0x0307
+#define GL_SRC_ALPHA_SATURATE 0x0308
+
 // Culled face side
 #define GL_FRONT 0x0404
 #define GL_BACK 0x0405
@@ -65,6 +78,12 @@ extern "C" {
 #define GL_COMPILE 0x1300
 #define GL_COMPILE_AND_EXECUTE 0x1301
 
+// More blend factors
+#define GL_CONSTANT_COLOR 0x8001
+#define GL_ONE_MINUS_CONSTANT_COLOR 0x8002
+#define GL_CONSTANT_ALPHA 0x8003
+#define GL_ONE_MINUS_CONSTANT_ALPHA 0x8004
+
 //
 // OpenGL typedefs
 //
@@ -126,6 +145,7 @@ GLAPI void glEndList(void);
 GLAPI void glNewList(GLuint list, GLenum mode);
 GLAPI void glFlush();
 GLAPI void glFinish();
+GLAPI void glBlendFunc(GLenum sfactor, GLenum dfactor);
 
 #ifdef __cplusplus
 }

Userland/Libraries/LibGL/GLBlend.cpp

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "GL/gl.h"
+#include "GLContext.h"
+
+extern GL::GLContext* g_gl_context;
+
+void glBlendFunc(GLenum sfactor, GLenum dfactor)
+{
+    return g_gl_context->gl_blend_func(sfactor, dfactor);
+}

Userland/Libraries/LibGL/GLContext.h

@@ -49,6 +49,7 @@ public:
     virtual void gl_new_list(GLuint list, GLenum mode) = 0;
     virtual void gl_flush() = 0;
     virtual void gl_finish() = 0;
+    virtual void gl_blend_func(GLenum src_factor, GLenum dst_factor) = 0;
 
     virtual void present() = 0;
 };

Userland/Libraries/LibGL/SoftwareGLContext.cpp

@@ -859,6 +859,57 @@ void SoftwareGLContext::gl_finish()
     // No-op since SoftwareGLContext is completely synchronous at the moment
 }
 
+void SoftwareGLContext::gl_blend_func(GLenum src_factor, GLenum dst_factor)
+{
+    if (m_in_draw_state) {
+        m_error = GL_INVALID_OPERATION;
+        return;
+    }
+
+    // FIXME: The list of allowed enums differs between API versions
+    // This was taken from the 2.0 spec on https://docs.gl/gl2/glBlendFunc
+
+    if (!(src_factor == GL_ZERO
+            || src_factor == GL_ONE
+            || src_factor == GL_SRC_COLOR
+            || src_factor == GL_ONE_MINUS_SRC_COLOR
+            || src_factor == GL_DST_COLOR
+            || src_factor == GL_ONE_MINUS_DST_COLOR
+            || src_factor == GL_SRC_ALPHA
+            || src_factor == GL_ONE_MINUS_SRC_ALPHA
+            || src_factor == GL_DST_ALPHA
+            || src_factor == GL_ONE_MINUS_DST_ALPHA
+            || src_factor == GL_CONSTANT_COLOR
+            || src_factor == GL_ONE_MINUS_CONSTANT_COLOR
+            || src_factor == GL_CONSTANT_ALPHA
+            || src_factor == GL_ONE_MINUS_CONSTANT_ALPHA
+            || src_factor == GL_SRC_ALPHA_SATURATE)) {
+        m_error = GL_INVALID_ENUM;
+        return;
+    }
+
+    if (!(dst_factor == GL_ZERO
+            || dst_factor == GL_ONE
+            || dst_factor == GL_SRC_COLOR
+            || dst_factor == GL_ONE_MINUS_SRC_COLOR
+            || dst_factor == GL_DST_COLOR
+            || dst_factor == GL_ONE_MINUS_DST_COLOR
+            || dst_factor == GL_SRC_ALPHA
+            || dst_factor == GL_ONE_MINUS_SRC_ALPHA
+            || dst_factor == GL_DST_ALPHA
+            || dst_factor == GL_ONE_MINUS_DST_ALPHA
+            || dst_factor == GL_CONSTANT_COLOR
+            || dst_factor == GL_ONE_MINUS_CONSTANT_COLOR
+            || dst_factor == GL_CONSTANT_ALPHA
+            || dst_factor == GL_ONE_MINUS_CONSTANT_ALPHA)) {
+        m_error = GL_INVALID_ENUM;
+        return;
+    }
+
+    m_blend_source_factor = src_factor;
+    m_blend_destination_factor = dst_factor;
+}
+
 void SoftwareGLContext::present()
 {
     m_rasterizer.blit_to(*m_frontbuffer);

Userland/Libraries/LibGL/SoftwareGLContext.h

@@ -55,6 +55,7 @@ public:
     virtual void gl_new_list(GLuint list, GLenum mode) override;
     virtual void gl_flush() override;
     virtual void gl_finish() override;
+    virtual void gl_blend_func(GLenum src_factor, GLenum dst_factor) override;
 
     virtual void present() override;
 
@@ -105,6 +106,9 @@ private:
     GLenum m_front_face = GL_CCW;
     GLenum m_culled_sides = GL_BACK;
 
+    GLenum m_blend_source_factor = GL_ONE;
+    GLenum m_blend_destination_factor = GL_ZERO;
+
     NonnullRefPtr<Gfx::Bitmap> m_frontbuffer;
 
     Clipper m_clipper;