LibGL: Implement basic texture units

These are merely a way to hold the different texture target bind
points that a texture can be bound to.

Userland/Libraries/LibGL/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(SOURCES
     Tex/NameAllocator.cpp
     Tex/Texture2D.cpp
+    Tex/TextureUnit.cpp
     Clipper.cpp
     GLBlend.cpp
     GLColor.cpp

Userland/Libraries/LibGL/SoftwareGLContext.h

@@ -12,6 +12,7 @@
 #include "SoftwareRasterizer.h"
 #include "Tex/NameAllocator.h"
 #include "Tex/Texture.h"
+#include "Tex/TextureUnit.h"
 #include <AK/HashMap.h>
 #include <AK/RefPtr.h>
 #include <AK/Tuple.h>
@@ -138,6 +139,8 @@ private:
     // Texture objects
     TextureNameAllocator m_name_allocator;
     HashMap<GLuint, RefPtr<Texture>> m_allocated_textures;
+    Array<TextureUnit, 32> m_texture_units;
+    TextureUnit* m_active_texture_unit { &m_texture_units[0] };
 
     SoftwareRasterizer m_rasterizer;
 

Userland/Libraries/LibGL/Tex/TextureUnit.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibGL/GL/gl.h>
+#include <LibGL/Tex/TextureUnit.h>
+
+namespace GL {
+
+void TextureUnit::bind_texture_to_target(GLenum texture_target, const RefPtr<Texture>& texture)
+{
+    switch (texture_target) {
+    case GL_TEXTURE_2D:
+        m_texture_target_2d = texture;
+        m_currently_bound_texture = texture;
+        m_currently_bound_target = GL_TEXTURE_2D;
+        break;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+void TextureUnit::unbind_texture(GLenum texture_target)
+{
+    switch (texture_target) {
+    case GL_TEXTURE_2D:
+        m_texture_target_2d = nullptr;
+        m_currently_bound_target = 0;
+        break;
+    default:
+        VERIFY_NOT_REACHED();
+    }
+
+    m_currently_bound_texture = nullptr;
+}
+
+}

Userland/Libraries/LibGL/Tex/TextureUnit.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/OwnPtr.h>
+#include <LibGL/Tex/Texture2D.h>
+
+namespace GL {
+
+class TextureUnit {
+public:
+    TextureUnit() = default;
+
+    void bind_texture_to_target(GLenum texture_target, const RefPtr<Texture>& texture);
+    void unbind_texture(GLenum texture_target);
+    const RefPtr<Texture>& get_bound_texture() const { return m_currently_bound_texture; }
+
+    GLenum currently_bound_target() const { return m_currently_bound_target; }
+    bool is_bound() const { return m_currently_bound_texture != nullptr; }
+
+private:
+    RefPtr<Texture2D> m_texture_target_2d { nullptr };
+    RefPtr<Texture> m_currently_bound_texture { nullptr };
+    GLenum m_currently_bound_target;
+};
+
+}