From 95dba598268f82ffe0d1b180893cd2759d7a5827 Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Sat, 31 Oct 2020 14:39:38 +1000
Subject: [PATCH] libretro: Add MSAA options

---
 README.md                                     |  1 +
 src/common/string_util.h                      |  5 ++++
 .../libretro_host_interface.cpp               | 24 ++++++++++++++++++-
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 797d40801..1237c36e2 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@ A "BIOS" ROM image is required to to start the emulator and to play games. You c
 
 ## Latest News
 
+- 2020/10/31: Multisample antialiasing added as an enhancement.
 - 2020/10/30: Option to use analog stick as d-pad for analog controller added.
 - 2020/10/20: New cheat manager with memory scanning added. More features will be added over time.
 - 2020/10/05: CD-ROM read speedup enhancement added.
diff --git a/src/common/string_util.h b/src/common/string_util.h
index 891c689b8..f1a43111c 100644
--- a/src/common/string_util.h
+++ b/src/common/string_util.h
@@ -112,6 +112,11 @@ ALWAYS_INLINE static bool StartsWith(const std::string_view& str, const char* pr
 {
   return (str.compare(0, std::strlen(prefix), prefix) == 0);
 }
+ALWAYS_INLINE static bool EndsWith(const std::string_view& str, const char* suffix)
+{
+  const std::size_t suffix_length = std::strlen(suffix);
+  return (str.length() >= suffix_length && str.compare(str.length() - suffix_length, suffix_length, suffix) == 0);
+}
 
 #ifdef WIN32
 
diff --git a/src/duckstation-libretro/libretro_host_interface.cpp b/src/duckstation-libretro/libretro_host_interface.cpp
index 38d7f62f6..18e0699ba 100644
--- a/src/duckstation-libretro/libretro_host_interface.cpp
+++ b/src/duckstation-libretro/libretro_host_interface.cpp
@@ -457,7 +457,7 @@ void LibretroHostInterface::OnSystemDestroyed()
   m_using_hardware_renderer = false;
 }
 
-static std::array<retro_core_option_definition, 40> s_option_definitions = {{
+static std::array<retro_core_option_definition, 41> s_option_definitions = {{
   {"duckstation_Console.Region",
    "Console Region",
    "Determines which region/hardware to emulate. Auto-Detect will use the region of the disc inserted.",
@@ -559,6 +559,23 @@ static std::array<retro_core_option_definition, 40> s_option_definitions = {{
     {"15", "15x"},
     {"16", "16x"}},
    "1"},
+  {"duckstation_GPU.MSAA",
+   "Multisample Antialiasing",
+   "Uses multisample antialiasing for rendering 3D objects. Can smooth out jagged edges on polygons at a lower "
+   "cost to performance compared to increasing the resolution scale, but may be more likely to cause rendering "
+   "errors in some games.",
+   {{"1", "Disabled"},
+    {"2", "2x MSAA"},
+    {"4", "4x MSAA"},
+    {"8", "8x MSAA"},
+    {"16", "16x MSAA"},
+    {"32", "32x MSAA"},
+    {"2-ssaa", "2x SSAA"},
+    {"4-ssaa", "4x SSAA"},
+    {"8-ssaa", "8x SSAA"},
+    {"16-ssaa", "16x SSAA"},
+    {"32-ssaa", "32x SSAA"}},
+   "1"},
   {"duckstation_GPU.TrueColor",
    "True Color Rendering",
    "Disables dithering and uses the full 8 bits per channel of color information. May break rendering in some games.",
@@ -781,6 +798,11 @@ void LibretroHostInterface::LoadSettings()
   g_settings.cpu_overclock_enable = (overclock_percent != 100);
   g_settings.UpdateOverclockActive();
 
+  // convert msaa settings
+  const std::string msaa = si.GetStringValue("GPU", "MSAA", "1");
+  g_settings.gpu_multisamples = StringUtil::FromChars<u32>(msaa).value_or(1);
+  g_settings.gpu_per_sample_shading = StringUtil::EndsWith(msaa, "-ssaa");
+
   // Ensure we don't use the standalone memcard directory in shared mode.
   for (u32 i = 0; i < NUM_CONTROLLER_AND_CARD_PORTS; i++)
     g_settings.memory_card_paths[i] = GetSharedMemoryCardPath(i);