Micscellaneous cleanup/fixes:

machine/z80scc.cpp: Fixed a cast-to-bool that broke detection of changes
to one register bit.

formats/fsmeta.cpp: Use visitors with variants where it makes sense.

docs: Updated minimum required SDL version to 2.0.6 for all targets,
added note that Python 3 is included with Xcode and updated instructions
for downloading stand-alone Python 3 for macOS.

ksys573.cpp: Don't create an insane number of textures for fghtmn and
pnchman internal artwork.

Tidied another batch of slot machine layouts.

docs/source/initialsetup/compilingmame.rst

@@ -72,7 +72,7 @@ building MAME on a 64-bit system.  Instructions may need to be adjusted for
   use the portable SDL (Simple DirectMedia Layer) interfaces instead, you can
   add **OSD=sdl** to the make options.  The main emulator binary will have an
   ``sdl`` prefix prepended (e.g. ``sdlmame.exe``).  You
-  will need to install the MSYS2 packages for SDL 2 version 2.0.3 or later.
+  will need to install the MSYS2 packages for SDL 2 version 2.0.6 or later.
 * By default, MAME will include the native Windows debugger.  To also include
   the portable Qt debugger, add **USE_QTDEBUG=1** to the make options.  You
   will need to install the MSYS2 packages for Qt 5.
@@ -224,7 +224,7 @@ Fedora Linux
 ------------
 
 You’ll need a few prerequisites from your Linux distribution.  Make sure you get
-SDL2 2.0.4 or later as earlier versions are buggy::
+SDL2 2.0.6 or later as earlier versions lack required functionality::
 
     sudo dnf install gcc gcc-c++ SDL2-devel SDL2_ttf-devel libXi-devel libXinerama-devel qt5-qtbase-devel qt5-qttools expat-devel fontconfig-devel alsa-lib-devel pulseaudio-libs-devel
 
@@ -246,7 +246,7 @@ Debian and Ubuntu (including Raspberry Pi and ODROID devices)
 -------------------------------------------------------------
 
 You’ll need a few prerequisites from your Linux distribution.  Make sure you get
-SDL2 2.0.4 or later as earlier versions are buggy::
+SDL2 2.0.6 or later as earlier versions lack required functionality::
 
     sudo apt-get install git build-essential python libsdl2-dev libsdl2-ttf-dev libfontconfig-dev libpulse-dev qt5-default
 
@@ -274,8 +274,10 @@ Apple macOS
 
 You’ll need a few prerequisites to get started. Make sure you’re on OS X 10.14
 Mojave or later for Intel Macs or macOS 11.0 Big Sur for Apple Silicon. You will
-need SDL2 2.0.4 or later for Intel or SDL2 2.0.14 on Apple Silicon.  You’ll also
-need to install Python 3.
+need SDL2 2.0.6 or later for Intel or SDL2 2.0.14 on Apple Silicon.  You’ll also
+need to install Python 3 – it’s currently included with the Xcode command line
+tools, but you can also install a stand-alone version or get it via the Homebrew
+package manager.
 
 * Install **Xcode** from the Mac App Store or
   `ADC <https://developer.apple.com/download/more/>`_ (AppleID required).
@@ -298,12 +300,13 @@ Next you’ll need to get SDL2 installed.
   **SDL2.framework** folder from the SDL disk image into the **Frameworks**
   folder. You will have to authenticate with your user password.
 
-Now get Python 3 set up:
+If you don’t already have it, get Python 3 set up:
 
-* Go to the `official Python site <https://www.python.org/>`_ and click the link
-  to the download page for the current version (this was
-  `Python 3.10.0 <https://www.python.org/downloads/release/python-3100/>`_ at
-  the time of writing).
+* Go to the official Python site, navigate to the
+  `releases for macOS <https://www.python.org/downloads/macos/>`_, and click the
+  link to download the installer for the latest stable release (this was
+  `Python 3.10.4 <https://www.python.org/ftp/python/3.10.4/python-3.10.4-macos11.pkg>`_
+  at the time of writing).
 * Scroll down to the “Files” section, and download the macOS version (called
   “macOS 64-bit universal2 installer” or similar).
 * Once the package downloads, open it and follow the standard installation

src/devices/machine/z80scc.cpp

@@ -2287,7 +2287,7 @@ void z80scc_channel::do_sccreg_wr15(uint8_t data)
 	LOG("Tx underr./EOM ints: %s\n", data & WR15_TX_EOM      ? WR15NO : "disabled");
 	LOG("Break/Abort ints   : %s\n", data & WR15_BREAK_ABORT ? WR15NO : "disabled");
 
-	const bool old_reg = m_wr15;
+	const uint8_t old_reg = m_wr15;
 	m_wr15 = data;
 	if ((old_reg & WR15_ZEROCOUNT) != (m_wr15 & WR15_ZEROCOUNT))
 	{

src/lib/formats/fsmeta.cpp

@@ -34,48 +34,37 @@ const char *meta_data::entry_name(meta_name name)
 	return "";
 }
 
-template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
-template<class... Ts> overloaded(Ts...)->overloaded<Ts...>;
+template <class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
+template <class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 
 meta_type meta_value::type() const
 {
 	std::optional<meta_type> result;
-	std::visit(overloaded
-	{
-		[&result](const std::string &)              { result = meta_type::string; },
-		[&result](std::uint64_t)                    { result = meta_type::number; },
-		[&result](bool)                             { result = meta_type::flag; },
-		[&result](const util::arbitrary_datetime &) { result = meta_type::date; }
-	}, value);
+	std::visit(
+			overloaded{
+				[&result] (const std::string &)              { result = meta_type::string; },
+				[&result] (std::uint64_t)                    { result = meta_type::number; },
+				[&result] (bool)                             { result = meta_type::flag; },
+				[&result] (const util::arbitrary_datetime &) { result = meta_type::date; } },
+			value);
 	return *result;
 }
 
 std::string meta_value::to_string() const
 {
 	std::string result;
-
-	switch (type())
-	{
-	case meta_type::string:
-		result = as_string();
-		break;
-	case meta_type::number:
-		result = util::string_format("0x%x", as_number());
-		break;
-	case meta_type::flag:
-		result = as_flag() ? "t" : "f";
-		break;
-	case meta_type::date:
-		{
-			auto dt = as_date();
-			result = util::string_format("%04d-%02d-%02d %02d:%02d:%02d",
-				dt.year, dt.month, dt.day_of_month,
-				dt.hour, dt.minute, dt.second);
-		}
-		break;
-	default:
-		throw false;
-	}
+	std::visit(
+			overloaded{
+				[&result] (const std::string &val)              { result = val; },
+				[&result] (std::uint64_t val)                   { result = util::string_format("0x%x", val); },
+				[&result] (bool val)                            { result = val ? "t" : "f"; },
+				[&result] (const util::arbitrary_datetime &val)
+				{
+					result = util::string_format("%04d-%02d-%02d %02d:%02d:%02d",
+						val.year, val.month, val.day_of_month,
+						val.hour, val.minute, val.second);
+				} },
+			value);
 	return result;
 }
 

src/lib/formats/fsmeta.h

@@ -103,10 +103,11 @@ struct meta_description {
 	meta_name m_name;
 	meta_value m_default;
 	bool m_ro;
-	std::function<void(const meta_value &)> m_validator;
+	std::function<void (const meta_value &)> m_validator;
 	const char *m_tooltip;
 
-	template<typename T> meta_description(meta_name name, T def, bool ro, std::function<void(meta_value)> validator, const char *tooltip) :
+	template <typename T>
+	meta_description(meta_name name, T def, bool ro, std::function<void(meta_value)> validator, const char *tooltip) :
 		meta_description(name, meta_value(def), ro, std::move(validator), tooltip)
 	{}