Libretro: build the core on PRs too, and ship its info file (#8)

* Libretro: build the core on PRs too, and ship its info file

The libretro core build is only wired into nightly_release.yml, so a PR or a
push can break pcsx2-libretro while Linux CI stays green -- you find out the
next morning. Call the same reusable workflow from linux_build_matrix.yml, so
the core is built alongside the Qt and SDL flavours on every PR and push.

Also add yaps2_libretro.info. Frontends read it for the core name, extensions,
BIOS requirements and feature flags, and it has to sit next to the .so, but it
never landed in the repo -- so the nightly ships a core with no info file.
Every field comes from pcsx2-libretro/Main.cpp: hw_render/required_hw_api
reflect the mandatory Vulkan context sharing (no software or GL fallback
toward the frontend), disk_control the .m3u and tray-swap support, and cheats
/memory_descriptors/input_descriptors are false because those interfaces are
not registered. The same file is proposed for libretro-super in
libretro/libretro-super#2013, so the two stay in sync.

* Libretro: dithering, trilinear, mipmapping and FXAA core options

Fill the graphics-option gap vs the pcee2/lrps2 cores: yaps2_dithering
(dithering_ps2 0/1/2), yaps2_trilinear_filtering (TriFilter enum, Automatic=-1),
yaps2_mipmapping (hw_mipmap) and yaps2_fxaa (fxaa), defaults matching the
base config. Both the v2 table and the legacy variables list carry them.

.github/workflows/linux_build_matrix.yml

@@ -2,8 +2,9 @@ name: 🐧 Linux Builds (aarch64)
 
 # yaps2 fork: we ship for ARM Linux handhelds only, so CI builds a single
 # platform — native aarch64 — in two flavours:
-#   * yaps2-qt   AppImage + tarball (desktop / dev + Rocknix / Batocera, which run Wayland)
-#   * yaps2-sdl  handheld tarball    (bare-kmsdrm handhelds; VK_KHR_display direct-display)
+#   * yaps2-qt        AppImage + tarball (desktop / dev + Rocknix / Batocera, which run Wayland)
+#   * yaps2-sdl       handheld tarball    (bare-kmsdrm handhelds; VK_KHR_display direct-display)
+#   * yaps2-libretro  core .so            (RetroArch and other libretro frontends)
 
 on:
   push:
@@ -32,3 +33,11 @@ jobs:
       jobName: "SDL Handheld Build (arm64)"
       artifactPrefixName: "yaps2-linux-arm64-sdl"
     secrets: inherit
+
+  build_linux_libretro:
+    name: "libretro Core"
+    uses: ./.github/workflows/linux_build_libretro.yml
+    with:
+      jobName: "libretro Core Build (arm64)"
+      artifactPrefixName: "yaps2-linux-arm64-libretro"
+    secrets: inherit

pcsx2-libretro/Main.cpp

@@ -872,6 +872,20 @@ static struct retro_core_option_v2_definition kOptionDefinitions[] = {
 		nullptr, "video",
 		{{"Minimum", nullptr}, {"Basic", nullptr}, {"Medium", nullptr}, {"High", nullptr},
 			{"Full", nullptr}, {"Maximum", nullptr}, {nullptr, nullptr}}, "Basic"},
+	{"yaps2_dithering", "Dithering", "Dithering",
+		"Unscaled replicates PS2 dithering; Off can reduce banding artifacts at higher internal resolutions.",
+		nullptr, "video",
+		{{"Unscaled", nullptr}, {"Off", nullptr}, {"Scaled", nullptr}, {nullptr, nullptr}}, "Unscaled"},
+	{"yaps2_trilinear_filtering", "Trilinear Filtering", "Trilinear Filtering",
+		nullptr, nullptr, "video",
+		{{"Automatic", nullptr}, {"Off", nullptr}, {"Trilinear (PS2)", nullptr},
+			{"Trilinear (Forced)", nullptr}, {nullptr, nullptr}}, "Automatic"},
+	{"yaps2_mipmapping", "Hardware Mipmapping", "Hardware Mipmapping",
+		nullptr, nullptr, "video",
+		{{"enabled", nullptr}, {"disabled", nullptr}, {nullptr, nullptr}}, "enabled"},
+	{"yaps2_fxaa", "FXAA", "FXAA",
+		"Cheap post-process anti-aliasing.", nullptr, "video",
+		{{"disabled", nullptr}, {"enabled", nullptr}, {nullptr, nullptr}}, "disabled"},
 	{"yaps2_texture_filtering", "Texture Filtering", "Texture Filtering",
 		"Bilinear (PS2) filters as the game requests. Forced filters everything, which smooths textures "
 		"but can blur 2D elements; the sprite-excluding variant protects UI sprites.",
@@ -947,6 +961,10 @@ static struct retro_variable kCoreVariables[] = {
 	{"yaps2_no_interlacing_patches", "No-interlacing patches (restart); disabled|enabled"},
 	{"yaps2_widescreen_patches", "Widescreen patches (restart); disabled|enabled"},
 	{"yaps2_blending_accuracy", "Blending accuracy; Basic|Minimum|Medium|High|Full|Maximum"},
+	{"yaps2_dithering", "Dithering; Unscaled|Off|Scaled"},
+	{"yaps2_trilinear_filtering", "Trilinear filtering; Automatic|Off|Trilinear (PS2)|Trilinear (Forced)"},
+	{"yaps2_mipmapping", "Hardware mipmapping; enabled|disabled"},
+	{"yaps2_fxaa", "FXAA; disabled|enabled"},
 	{"yaps2_texture_filtering", "Texture filtering; Bilinear (PS2)|Nearest|Bilinear (Forced)|Bilinear (Forced excluding sprites)"},
 	{"yaps2_anisotropic_filtering", "Anisotropic filtering; 0|2|4|8|16"},
 	{"yaps2_sw_threads", "Software renderer threads; 2|0|1|3|4"},
@@ -1097,6 +1115,45 @@ static void ApplyCoreOptions(bool startup)
 			}
 		}
 
+		var = {"yaps2_dithering", nullptr};
+		if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+		{
+			// Values match the Dithering config field: 0=Off, 1=Scaled, 2=Unscaled.
+			static constexpr std::pair<const char*, int> kDither[] = {{"Off", 0}, {"Scaled", 1}, {"Unscaled", 2}};
+			for (const auto& [name, value] : kDither)
+			{
+				if (!std::strcmp(var.value, name))
+				{
+					s_base_settings->SetIntValue("EmuCore/GS", "dithering_ps2", value);
+					break;
+				}
+			}
+		}
+
+		var = {"yaps2_trilinear_filtering", nullptr};
+		if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+		{
+			// Values match the TriFiltering enum (Automatic=-1).
+			static constexpr std::pair<const char*, int> kTri[] = {
+				{"Automatic", -1}, {"Off", 0}, {"Trilinear (PS2)", 1}, {"Trilinear (Forced)", 2}};
+			for (const auto& [name, value] : kTri)
+			{
+				if (!std::strcmp(var.value, name))
+				{
+					s_base_settings->SetIntValue("EmuCore/GS", "TriFilter", value);
+					break;
+				}
+			}
+		}
+
+		var = {"yaps2_mipmapping", nullptr};
+		if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+			s_base_settings->SetBoolValue("EmuCore/GS", "hw_mipmap", !std::strcmp(var.value, "enabled"));
+
+		var = {"yaps2_fxaa", nullptr};
+		if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+			s_base_settings->SetBoolValue("EmuCore/GS", "fxaa", !std::strcmp(var.value, "enabled"));
+
 		var = {"yaps2_ee_cycle_rate", nullptr};
 		if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
 		{

yaps2_libretro.info

@@ -0,0 +1,44 @@
+# Software Information
+display_name = "Sony - PlayStation 2 (yaps2)"
+authors = "PCSX2 Team|bmdhacks|WizzardSK"
+supported_extensions = "elf|iso|ciso|chd|cso|zso|bin|mdf|nrg|dump|gz|img|irx|m3u"
+corename = "yaps2"
+categories = "Emulator"
+license = "GPLv3"
+permissions = ""
+display_version = "Git"
+
+# Hardware Information
+manufacturer = "Sony"
+systemname = "Sony PlayStation 2"
+systemid = "playstation2"
+
+# Libretro Features
+database = "Sony - PlayStation 2"
+supports_no_game = "false"
+savestate = "true"
+savestate_features = "basic"
+cheats = "false"
+input_descriptors = "false"
+memory_descriptors = "false"
+libretro_saves = "false"
+core_options = "true"
+core_options_version = "2.0"
+load_subsystem = "false"
+hw_render = "true"
+required_hw_api = "Vulkan >= 1.1"
+needs_fullpath = "true"
+disk_control = "true"
+is_experimental = "true"
+
+# Firmware / BIOS
+firmware_count = 2
+firmware0_desc = "'pcsx2/bios' folder (any valid PS2 BIOS dump, e.g. scph39001.bin)"
+firmware0_path = "pcsx2/bios"
+firmware0_opt = "false"
+firmware1_desc = "'pcsx2/resources' folder (shaders, GameIndex.yaml, fonts)"
+firmware1_path = "pcsx2/resources"
+firmware1_opt = "false"
+notes = "[1] This only checks that the folders exist in the correct location.|[2] The core does not require a specific BIOS filename, so this info file|[^] cannot tell you whether the content of your 'bios' folder is correct.|[3] The 'resources' folder must be copied from a matching yaps2/PCSX2 build;|[^] the core will not boot without it.|[4] The core is Vulkan-only: the frontend's Vulkan context is shared with the|[^] emulator through the hardware-render negotiation interface."
+
+description = "A libretro port of yaps2, a PlayStation 2 emulator forked from PCSX2 and aimed at ARM handhelds (working arm64 recompilers, Adreno fixes). The core renders through the frontend's own Vulkan context -- it takes the VkInstance and VkPhysicalDevice from the hardware-render context-negotiation interface and hands finished frames back through set_image -- so a Vulkan-capable driver is required and no other video driver will work. Place a PS2 BIOS dump in 'system/pcsx2/bios' and a copy of the emulator's 'resources' directory in 'system/pcsx2/resources'. Save states, .m3u disc swapping and the usual renderer/upscale/speedhack core options are implemented. This core is experimental."