LibGL+LibSoftGPU: Implement fixed pipeline support for `GL_COMBINE`

`GL_COMBINE` is basically a fixed function calculator to perform simple
arithmetics on configurable fragment sources. This patch implements a
number of texture env parameters with support for the RGBA internal
format.

2 files changed, 51 insertions, 3 deletions

diff --git a/Userland/Libraries/LibGPU/DeviceInfo.h b/Userland/Libraries/LibGPU/DeviceInfo.h
index 3693bc820d..6e39a0001e 100644
--- a/Userland/Libraries/LibGPU/DeviceInfo.h
+++ b/Userland/Libraries/LibGPU/DeviceInfo.h
@@ -16,6 +16,7 @@ struct DeviceInfo final {
     unsigned num_texture_units;
     unsigned num_lights;
     unsigned max_clip_planes;
+    float max_texture_lod_bias;
     u8 stencil_bits;
     bool supports_npot_textures;
     bool supports_texture_env_add;
diff --git a/Userland/Libraries/LibGPU/SamplerConfig.h b/Userland/Libraries/LibGPU/SamplerConfig.h
index a4b5b140d6..898bdfb3b0 100644
--- a/Userland/Libraries/LibGPU/SamplerConfig.h
+++ b/Userland/Libraries/LibGPU/SamplerConfig.h
@@ -1,11 +1,13 @@
 /*
  * Copyright (c) 2022, Stephan Unverwerth <s.unverwerth@serenityos.org>
+ * Copyright (c) 2022, Jelle Raaijmakers <jelle@gmta.nl>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #pragma once
 
+#include <AK/Array.h>
 #include <LibGPU/Image.h>
 #include <LibGfx/Vector4.h>
 
@@ -31,22 +33,67 @@ enum class TextureWrapMode {
 };
 
 enum class TextureEnvMode {
+    Add,
+    Blend,
+    Combine,
+    Decal,
     Modulate,
     Replace,
-    Decal,
+};
+
+enum class TextureCombinator {
     Add,
+    AddSigned,
+    Dot3RGB,
+    Dot3RGBA,
+    Interpolate,
+    Modulate,
+    Replace,
+    Subtract,
+};
+
+enum class TextureOperand {
+    OneMinusSourceAlpha,
+    OneMinusSourceColor,
+    SourceAlpha,
+    SourceColor,
+};
+
+enum class TextureSource {
+    Constant,
+    Previous,
+    PrimaryColor,
+    Texture,
+    TextureStage,
+};
+
+struct FixedFunctionTextureEnvironment final {
+    TextureCombinator alpha_combinator { TextureCombinator::Modulate };
+    Array<TextureOperand, 3> alpha_operand { TextureOperand::SourceAlpha, TextureOperand::SourceAlpha, TextureOperand::SourceAlpha };
+    float alpha_scale { 1.f };
+    Array<TextureSource, 3> alpha_source { TextureSource::Texture, TextureSource::Previous, TextureSource::Constant };
+    u8 alpha_source_texture_stage { 0 };
+    // FIXME: color is never actually updated
+    FloatVector4 color { 0.f, 0.f, 0.f, 0.f };
+    TextureEnvMode env_mode { TextureEnvMode::Modulate };
+    TextureCombinator rgb_combinator { TextureCombinator::Modulate };
+    Array<TextureOperand, 3> rgb_operand { TextureOperand::SourceColor, TextureOperand::SourceColor, TextureOperand::SourceAlpha };
+    float rgb_scale { 1.f };
+    Array<TextureSource, 3> rgb_source { TextureSource::Texture, TextureSource::Previous, TextureSource::Constant };
+    u8 rgb_source_texture_stage { 0 };
 };
 
 struct SamplerConfig final {
     RefPtr<Image> bound_image;
+    float level_of_detail_bias { 0.f };
     MipMapFilter mipmap_filter { MipMapFilter::Nearest };
     TextureFilter texture_mag_filter { TextureFilter::Linear };
     TextureFilter texture_min_filter { TextureFilter::Linear };
     TextureWrapMode texture_wrap_u { TextureWrapMode::Repeat };
     TextureWrapMode texture_wrap_v { TextureWrapMode::Repeat };
     TextureWrapMode texture_wrap_w { TextureWrapMode::Repeat };
-    FloatVector4 border_color { 0, 0, 0, 1 };
-    TextureEnvMode fixed_function_texture_env_mode { TextureEnvMode::Modulate };
+    FloatVector4 border_color { 0.f, 0.f, 0.f, 1.f };
+    FixedFunctionTextureEnvironment fixed_function_texture_environment {};
 };
 
 }