renderer: add area sampling scaling method (#201)

Adds Area Sampling to the list of scaling options. Works well to achieve a high-quality, smooth super-sampling effect. Dolphin has had this for a while and so has Ryujinx, so lui decided to port it.

Adapted from these two PRs:
https://github.com/Ryujinx/Ryujinx/pull/7304
https://github.com/dolphin-emu/dolphin/pull/11999

Credit: Torzu, lui

Reviewed-on: http://vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion/torzu-emu/torzu/pulls/57
Co-authored-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>
Co-committed-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>

Co-authored-by: lui <lui@vub63vv26q6v27xzv2dtcd25xumubshogm67yrpaz2rculqxs7jlfqad.onion>
Co-authored-by: crueter <swurl@swurl.xyz>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/201
Co-authored-by: JPikachu <jpikachu.eden@gmail.com>
Co-committed-by: JPikachu <jpikachu.eden@gmail.com>

src/video_core/renderer_opengl/gl_blit_screen.cpp

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -86,6 +92,9 @@ void BlitScreen::CreateWindowAdapt() {
     case Settings::ScalingFilter::ScaleForce:
         window_adapt = MakeScaleForce(device);
         break;
+    case Settings::ScalingFilter::Area:
+        window_adapt = MakeArea(device);
+        break;
     case Settings::ScalingFilter::Fsr:
     case Settings::ScalingFilter::Bilinear:
     default:

src/video_core/renderer_opengl/present/filters.cpp

@@ -1,8 +1,15 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "video_core/host_shaders/opengl_present_frag.h"
 #include "video_core/host_shaders/opengl_present_scaleforce_frag.h"
+#include "video_core/host_shaders/present_area_frag.h"
 #include "video_core/host_shaders/present_bicubic_frag.h"
 #include "video_core/host_shaders/present_gaussian_frag.h"
 #include "video_core/renderer_opengl/present/filters.h"
@@ -36,4 +43,9 @@ std::unique_ptr<WindowAdaptPass> MakeScaleForce(const Device& device) {
         fmt::format("#version 460\n{}", HostShaders::OPENGL_PRESENT_SCALEFORCE_FRAG));
 }
 
+std::unique_ptr<WindowAdaptPass> MakeArea(const Device& device) {
+    return std::make_unique<WindowAdaptPass>(device, CreateBilinearSampler(),
+                                             HostShaders::PRESENT_AREA_FRAG);
+}
+
 } // namespace OpenGL

src/video_core/renderer_opengl/present/filters.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -13,5 +19,6 @@ std::unique_ptr<WindowAdaptPass> MakeBilinear(const Device& device);
 std::unique_ptr<WindowAdaptPass> MakeBicubic(const Device& device);
 std::unique_ptr<WindowAdaptPass> MakeGaussian(const Device& device);
 std::unique_ptr<WindowAdaptPass> MakeScaleForce(const Device& device);
+std::unique_ptr<WindowAdaptPass> MakeArea(const Device& device);
 
 } // namespace OpenGL

src/video_core/renderer_opengl/present/present_uniforms.h

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -10,6 +16,7 @@ namespace OpenGL {
 constexpr GLint PositionLocation = 0;
 constexpr GLint TexCoordLocation = 1;
 constexpr GLint ModelViewMatrixLocation = 0;
+constexpr GLint ScreenSizeLocation = 1;
 
 struct ScreenRectVertex {
     constexpr ScreenRectVertex() = default;

src/video_core/renderer_opengl/present/window_adapt_pass.cpp

@@ -1,3 +1,9 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: Copyright 2024 Torzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2024 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -110,6 +116,9 @@ void WindowAdaptPass::DrawToFramebuffer(ProgramManager& program_manager, std::li
         glBindTextureUnit(0, textures[i]);
         glProgramUniformMatrix3x2fv(vert.handle, ModelViewMatrixLocation, 1, GL_FALSE,
                                     matrices[i].data());
+        glProgramUniform2ui(frag.handle, ScreenSizeLocation,
+                            static_cast<GLuint>(layout.screen.GetWidth()),
+                            static_cast<GLuint>(layout.screen.GetHeight()));
         glNamedBufferSubData(vertex_buffer.handle, 0, sizeof(vertices[i]), std::data(vertices[i]));
         glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
     }