Implement texture filters in GL renderer

include/config.hpp

@@ -16,6 +16,8 @@ struct EmulatorConfig {
 	bool shaderJitEnabled = shaderJitDefault;
 	bool discordRpcEnabled = false;
 	RendererType rendererType = RendererType::OpenGL;
+	TextureFilter textureFilter = TextureFilter::Auto;
+
 	Audio::DSPCore::Type dspType = Audio::DSPCore::Type::Null;
 
 	bool sdCardInserted = true;
@@ -34,4 +36,7 @@ struct EmulatorConfig {
 	EmulatorConfig(const std::filesystem::path& path);
 	void load();
 	void save();
+
+	static TextureFilter textureFilterFromString(std::string str);
+	static std::string textureFilterToString(TextureFilter filter);
 };

include/renderer.hpp

@@ -19,6 +19,12 @@ enum class RendererType : s8 {
 	Software = 3,
 };
 
+enum class TextureFilter {
+	Auto = 0,
+	ForceNearest,
+	ForceBilinear,
+};
+
 class GPU;
 struct SDL_Window;
 
@@ -44,6 +50,7 @@ class Renderer {
 	// We initialize it to the 3DS resolution by default and the frontend can notify us if it changes via the setOutputSize function
 	u32 outputWindowWidth = 400;
 	u32 outputWindowHeight = 240 * 2;
+	TextureFilter filterSetting = TextureFilter::Auto;
 
   public:
 	Renderer(GPU& gpu, const std::array<u32, regNum>& internalRegs, const std::array<u32, extRegNum>& externalRegs);
@@ -91,4 +98,6 @@ class Renderer {
 		outputWindowWidth = width;
 		outputWindowHeight = height;
 	}
+
+	void setFiltering(TextureFilter value) { filterSetting = value; }
 };

src/config.cpp

@@ -1,5 +1,7 @@
 #include "config.hpp"
 
+#include <algorithm>
+#include <cctype>
 #include <cmath>
 #include <fstream>
 #include <map>
@@ -61,6 +63,9 @@ void EmulatorConfig::load() {
 
 			shaderJitEnabled = toml::find_or<toml::boolean>(gpu, "EnableShaderJIT", shaderJitDefault);
 			vsyncEnabled = toml::find_or<toml::boolean>(gpu, "EnableVSync", true);
+
+			auto textureFilterName = toml::find_or<std::string>(gpu, "TextureFilter", "Auto");
+			textureFilter = textureFilterFromString(textureFilterName);
 		}
 	}
 
@@ -122,6 +127,7 @@ void EmulatorConfig::save() {
 	data["General"]["UsePortableBuild"] = usePortableBuild;
 	data["GPU"]["EnableShaderJIT"] = shaderJitEnabled;
 	data["GPU"]["Renderer"] = std::string(Renderer::typeToString(rendererType));
+	data["GPU"]["TextureFilter"] = textureFilterToString(textureFilter);
 	data["GPU"]["EnableVSync"] = vsyncEnabled;
 	data["Audio"]["DSPEmulation"] = std::string(Audio::DSPCore::typeToString(dspType));
 	data["Audio"]["EnableAudio"] = audioEnabled;
@@ -136,3 +142,30 @@ void EmulatorConfig::save() {
 	file << data;
 	file.close();
 }
+
+std::string EmulatorConfig::textureFilterToString(TextureFilter filter) {
+	switch (filter) {
+		case TextureFilter::Auto: return "auto";
+		case TextureFilter::ForceNearest: return "nearest";
+		case TextureFilter::ForceBilinear: return "bilinear";
+		default: Helpers::warn("Invalid texture filter type"); return "auto";
+	}
+}
+
+TextureFilter EmulatorConfig::textureFilterFromString(std::string str) {
+	// Transform to lower-case to make the setting case-insensitive
+	std::transform(str.begin(), str.end(), str.begin(), [](unsigned char c) { return std::tolower(c); });
+
+	static const std::unordered_map<std::string, TextureFilter> map = {
+		{"auto", TextureFilter::Auto},
+		{"nearest", TextureFilter::ForceNearest},
+		{"bilinear", TextureFilter::ForceBilinear},
+	};
+
+	if (auto search = map.find(str); search != map.end()) {
+		return search->second;
+	}
+
+	printf("Invalid texture filtering type. Defaulting to auto\n");
+	return TextureFilter::Auto;
+}

src/core/PICA/gpu.cpp

@@ -106,6 +106,7 @@ void GPU::reset() {
 	externalRegs[Framebuffer1Select] = 0;
 
 	renderer->reset();
+	renderer->setFiltering(config.textureFilter);
 }
 
 // Call the correct version of drawArrays based on whether this is an indexed draw (first template parameter)

src/core/renderer_gl/renderer_gl.cpp

@@ -616,7 +616,15 @@ OpenGL::Texture RendererGL::getTexture(Texture& tex) {
 	if (buffer.has_value()) {
 		return buffer.value().get().texture;
 	} else {
-		const auto textureData = std::span{gpu.getPointerPhys<u8>(tex.location), tex.sizeInBytes()};  // Get pointer to the texture data in 3DS memory
+		// Get pointer to the texture data in 3DS memory
+		const auto textureData = std::span{gpu.getPointerPhys<u8>(tex.location), tex.sizeInBytes()};
+		// Override texture filtering if necessary by adjust the texunit config before uploading the texture
+		if (filterSetting == TextureFilter::ForceNearest) {
+			tex.config &= ~(0b110);  // Force nearest filtering
+		} else if (filterSetting == TextureFilter::ForceBilinear) {
+			tex.config |= 0b110;  // Force bilinear
+		}
+
 		Texture& newTex = textureCache.add(tex);
 		newTex.decodeTexture(textureData);