Gens/GS r7

Copyright (c) 1999-2002 by Stéphane Dallongeville
Copyright (c) 2003-2004 by Stéphane Akhoun
Copyright (c) 2008-2009 by David Korth

This version of Gens is maintained by David Korth.
E-mail: gerbilsoft@verizon.net

For news on Gens/GS, visit Sonic Retro:
http://www.sonicretro.org

================================================================

What is Gens/GS?

Gens/GS r7 is David Korth's fork of Gens, initially based on
Gens for Linux v2.15.2. The number after the "r" indicates the
Gens/GS release. Releases are usually made after a significant new
feature has been added, with minor releases if a major bug is found.

================================================================

This file contains information about previous versions of Gens/GS.
See NEWS.txt for information about the current version.

================================================================

What's new in Gens/GS v2.15.5/GS-m6?

Milestone 6 introduces the following new features:

- Mega Drive Plugins v0.1.0. The initial version of the plugin system
  only supports render plugins and only if they're built into the
  main executable. A later version will add support for external
  plugins (.dll on Windows, .so on Linux), as well as more types of
  plugins, such as netplay, debugging, and movie recording.

- doc/MDP.txt contains the MDP Interface Specifiction Version 0.1.0.
  This document is licensed under the GNU Free Documentation License v1.3.

- All renderers now support 32-bit color.

- [Win32] hq2x has been fixed.

- Scale2x now has optimized C and x86 mmx implementations.

- New renderers: Scale3x, Scale4x, hq3x, hq4x.

- Added a 32-bit color asm version of the Fast Blur effect, with mmx
  optimizations if available.

Milestone 6 fixes the following bugs:

- [SDL] Ctrl+Q did not work in fullscreen mode.

Milestone 6 has the following low-level code changes:

- Many x86 assembler files have been cleaned up. In particular, many of them
  no longer depend on the "nasmhead.inc" macro file. This macro file provided
  alignment macros (which nasm has built-in) and "DECL" macros, which provide
  both underscored and non-underscored symbol declarations. Only one of these
  is needed per symbol, and it depends on the executable format. Removing
  "DECL" and manually redefining symbols reduced the total symbol count.

- Adjusted alignment values for many x86 asm functions.

- Added alpha transparency support to ImageUtil::writePNG().

- Major overhaul for the ImageUtil::writeBMP() code. Changes include using
  a templated function for different color depths, using pointer arithmetic
  instead of recalculating array indexes for every iteration, and fixing a
  bug that caused bitmaps to be 54 bytes larger than they should have been.

- The "Render Fullscreen" and "Render Windowed" values in the gens.cfg file
  now contain the renderer tag instead of an ID number. For example, instead
  of saying "1" for the Normal renderer, the value would be "Normal".

================================================================

What's new in Gens/GS v2.15.5/GS-m5.3?

Milestone 5.3 fixes the following bugs:

- PIC compilation was broken due to the new CPU Flags code.

- nasm's -O3 optimization doesn't work properly on the Gens code with older
  versions of nasm. Gens now uses the -O1 optimization instead.

Milestone 5.3 has the following miscellaneous changes:

- [GTK+] Removed some unnecessary GDK includes.

================================================================

What's new in Gens/GS v2.15.5/GS-m5.2?

Milestone 5.2 introduces the following new features:

- Updates to the most-used renderers:

  - The C++ 1x, 2x, and 2x scanline renderers are now much faster.

  - The asm and mmx 1x and 2x renderers have been updated to support
    32-bit color.

  - The scanline and interpolated scanline asm renderers now correctly
    black out empty lines, which fixes a "leftover garbage" problem
    caused by the new text drawing function.

- [Linux] The OpenGL renderer now supports border color emulation.

- The "Stretch" option now allows you to set Horizontal Stretch and
  Vertical Stretch independently.

- New "General Options" window layout. The new layout takes up a lot less
  space than the old layout, and allows for more options.

- The "General Options" window now allows you to enable or disable
  border color emulation and the pause tint.

- [GTK+] The design of the "Controller Configuration" window has been
  improved.

- The "Auto Pause" feature has been reimplemented.

Milestone 5.2 has the following miscellaneous changes:

- The "BIOS/Misc Files" entries for "GCOffline" and "Gens Manual" have been
  removed. There are no functions in Gens/GS that make use of these, and both
  documents haven't been updated in several years.

- The 16 kHz, 32 kHz, and 48 kHz sound rates have been removed. They never
  worked properly and ended up causing lag.

- The built-in debugger now sleeps for 100 ms between frames. Previously, it
  would attempt to redraw frames as fast as possible, which led to high CPU
  usage if VSync wasn't turned on.

- [Win32] hq2x is broken, so it has been disabled for now.	

Milestone 5.2 fixes the following bugs:

- Fixed compilation with --disable-cdrom.

- Fixed some PWM regressions introduced in m5.1.

- [Win32] Savestates were sometimes not saved to the correct directory.

Milestone 5.2 has the following low-level code changes:

- VDraw_DDraw: CORRECT_256_ASPECT_RATIO and ALT_X_RATIO_RES have been removed.
  These were originally used in Gens Rerecording to specify if the horizontal
  resolution should always be stretched, but is no longer necessary due to the
  improved "Stretch" mode options.

- nasm now generates debugging symbols for all asm code.

- Many functions and variables that don't need global visibility have been
  marked as static.

- New CPU flag system to determine all available instruction sets instead of
  just MMX. This will allow for more optimizations later on.

- Fixed an issue where a segment override prefix was specified in Starscream,
  which broke Valgrind. (Valgrind is still broken for SegaCD and 32X emulation,
  unfortunately.)

================================================================

What's new in Gens/GS v2.15.5/GS-m5.1?

Milestone 5.1 introduces the following new features:

- RAR archives can now be used via an external RAR binary. You must have RAR
  installed in order to use this feature. (Windows users can install WinRAR,
  which includes the command-line rar.exe.)

- You can now drag a ROM file onto the Gens window to open it.

- [GTK+] Many of the bundled icons have been updated with KDE 4 Oxygen icons.
  See http://www.oxygen-icons.org/ for more information.

Milestone 5.1 has the following miscellaneous changes:

- "PSG Improved" has been renamed to "PSG (Sine Wave)", which more accurately
  describes its functionality.

Milestone 5.1 fixes the following bugs:

- [Win32] The lag issue seen on some computers should be fixed.

- [Win32] Fixed joystick POV support.

- [32X] PWM audio no longer "clicks" when it isn't in use.

- [Debugger] The VDP debugger now scrolls all the way to the last VRAM line,
  0xFE00-0xFFFF. Previously, it would only scroll to line 0xFC00-0xFDFF. This
  bug was reported by djohe in #retro.

- [Regression from m5] Gens no longer creates blank SRAM files for games that
  don't use SRAM. This bug was reported by Delta on the Sonic Retro forums.

- Fixed compilation with --disable-cdrom.

Milestone 5.1 has the following low-level code changes:

- The menu system has been rewritten such that both the Win32 and GTK+
  versions now share the same menu data. Not only does this reduce the
  amount of duplicated code, it makes it easier to add menu items and
  it reduces the amount of code needed to build and synchronize the menus.

- The PWM audio emulator has been rewritten in C. This rewrite was based on
  pwm.c from Gens Rerecording.

- The build system has been updated so that it automatically detects MacOS X
  and Cygwin, and adjusts compilation settings for those two platforms as
  necessary. Thanks to Sonicblur on the Sonic Retro forums for the MacOS X
  compatibility fixes.

- The About window has been converted to a C++ class.
  Eventually, all of the windows will be converted to C++ classes.

- The configure script will now check what hash table implementations are
  available at compile time. Previously, Gens/GS only used the relatively
  new TR1 unordered_map, which is only available in gcc-4.x and later. Not
  only did this cause problems for gcc-3.x users, it caused problems for
  gcc-4.0 users, since unordered_map was broken in gcc-4.0. The configure
  script will now check to make sure unordered_map is working, and if it
  isn't, it will fall back to either __gnu_cxx::hash_map or std::map. If
  it falls back to std::map, it will print a warning, since std::map is
  not a hash table and is thus considerably slower than both unordered_map
  and hash_map.

- The configure script will now check if the linker supports --as-needed.
  Previously, the configure script always added --as-needed to LDFLAGS, which
  caused a problem on systems that didn't support it.

================================================================

What's new in Gens/GS v2.15.5/GS-m5?

Milestone 5 introduces the following new features:

- The Windows UI and DirectX code has been integrated into the codebase.
  The Gens/GS codebase can now be used to compile both the Linux versions
  and the Windows versions.

- [Linux] The frame counter code has been updated to work a lot better.
  In particular, it no longer uses the x86 instruction "rdtsc", so it
  should be more accurate on multiprocessor and multicore systems.

- 7z: A warning dialog is now shown if the 7z binary cannot be run. This
  usually occurs if 7-Zip isn't installed.

- [GTK+] The "General Options" dialog now has regular buttons instead of
  radio buttons for selecting colors. It seems that most GTK+ themes don't
  properly support changing the colors of radio buttons, so changing them
  to regular buttons enables proper color support.

Milestone 5 fixes the following bugs:

- [32X] PWM audio volume has been increased by a factor of 4, making it audible.

- [SegaCD] The 8th PCM audio channel now works.

- [Linux] If Gens is started in a terminal window, Ctrl-C now correctly
  shuts down the program. Earlier versions ignored Ctrl-C. Apparently,
  SDL catches the Ctrl-C (SIGINT) and adds it to the SDL event queue as
  an SDL_QUIT message.

- The "Save Config" and "Load Config As" functions incorrectly passed a
  NULL value to the GensUI class when a C++ string was expected, resulting
  in a crash.

- Clicking "OK" in the "Archive File Selection" dialog with no file selected
  resulted in a crash.

- [32X] Some 32X ROMs were misdetected as Genesis ROMs. In particular, drx's
  "Sonic 32X" does not say "SEGA 32X" in the header. However, the ROM does
  have "MARS" at 0x040E. The detection function has been updated to take
  this into account, so "Sonic 32X" is now properly detected as a 32X ROM.

- [GTK+] Fixed GTK+ 2.4 compatibility issues.

- [GTK+] Added accelerators for the "Cancel" and "Save" buttons in the
  Game Genie window.

- Color Adjust: If both Contrast and Brightness are set to 0, then no color
  adjustment calculations will take place. This prevents inaccuracies due to
  rounding errors.

Milestone 5 has the following low-level code changes:

- -Wl,--as-needed has been added to LDFLAGS. This eliminates unnecessary
  library dependencies.

- Internal copies of zlib and libpng have been added. These internal copies
  are not used by default on the Linux build, since most Linux systems have
  zlib and libpng already installed, but are used by default on the Windows
  build. Use of these internal copies can be configured using the ./configure
  script.

- MP3 playback support can now be disabled in the ./configure script.

- rom.cpp, save.cpp, and imageutil.cpp (formerly scrshot.c) have been
  converted to static C++ classes.

- The INI parser now supports hexadecimal and octal numbers. These numbers
  are identified by prefixes. (Hexadecimal: "0x" or "0X"; Octal: "0".)
  
- Controller mappings are now saved as hexadecimal numbers in gens.cfg.

Milestone 5 has the following known issues:

- [Win32] MP3 support is currently disabled due to problems with the MP3
  library. ASPI support is available though, so you can use an ASPI library
  with a CD-ROM emulator, such as Daemon Tools.

- [Win32] Stretched rendering may not work properly in fullscreen mode.

- [Linux] Monaural sound is broken.

================================================================

What's new in Gens for Linux v2.15.4/GS-m4.2?

Milestone 4.2 fixes the following bugs:

- Joystick input was still completely broken due to an accidental swapping
  of "which" (device number) and "axis" (axis number). This bug was
  reported by Techokami in #retro.

================================================================

What's new in Gens for Linux v2.15.4/GS-m4.1?

Milestone 4.1 introduces the following new features:

- The Fast Forward feature has been re-enabled. It is mapped to F1.
  Note that Fast Forward doesn't work if VSync is enabled.

Milestone 4.1 fixes the following bugs:

- SDL's joystick handler wasn't being initialized properly. Joysticks
  were properly detected in the Controller Configuration window, but
  didn't work in-game. This bug was reported by Techokami in #retro.

- A missing #include <stdlib.h> line has been added to g_main_linux.hpp.
  Lack of this line led to compilation failures on some machines.
  This bug was reported by SOTI in #retro.

- zlib support can now be conditionally compiled. This only affects the
  GZip and Zip functionality; PNG support implies zlib, but enabling PNG
  support will not implicitly enable zlib support.

================================================================

What's new in Gens for Linux v2.15.4/GS-m4?

Milestone 4 introduces the following new features:

- The SegaCD GFX debugger now shows all 16 virtual palette lines. The
  virtual palette lines include highlight and shadow. Previously, these
  lines were selectable, and the patterns did reflect the palettes, but
  the color lines didn't actually show up.

- MAME CHD and CCnet support have been removed. They weren't used for
  anything and simply took up extra space.

- The scanline renderer is now available in 32-bit color. Note that the
  x86 asm scanline renderers don't erase the scanlines on every frame,
  so garbage is left behind by the new text drawing function.

- OpenGL linear filtering can now be enabled/disabled via a menu item.

- New generic input and audio layers, which are located in src/gens/input/
  and src/gens/audio/. Like VDraw, which was implemented in Milestone 3,
  this will make it easier to add support for DirectInput and DirectSound,
  respectively. src/gens/sdllayer/ is now completely gone.

- New onscreen text drawing function. The new function draws text to the
  display framebuffer rather than to the emulated framebuffer. Among other
  things, this means that messages and the FPS counter no longer show up
  in screenshots. The font currently used is the Commodore 64 font, but
  more fonts may be added later on.

- 32-bit color support in the VDP debugger.

- Improved OpenGL renderer. The improved renderer takes some fixes from
  Gens/Linux 2.15.4, as well as improving the VSync functionality. VSync
  uses the GLX_SGI_swap_control extension, so it may not work on all
  systems. Support for other VSync extensions will be added later on.

- The GTK+ window border is now set to 0. This allows a window manager to
  remove the window border for pseudo-full-screen.

Milestone 4 fixes the following bugs:

- Shadow/Highlight colors were incorrect in 16-bit color.

- If the country code was set to US, Gens/GS would incorrectly attempt to
  load the EU MegaCD BIOS if a SegaCD game was loaded, resulting in a
  region code error. This has been fixed.

- Physical CD-ROM support via ASPI works again. I accidentally broke it
  when CD-ROM support was made conditional.

Milestone 4 has the following low-level code changes:

- C99 mode is now used by default for C-language code.

- The new INI handler has been converted to a C++ class.

- Deprecated GTK+ functions have been disabled via the
  -DGTK_DISABLE_DEPRECATED CFLAG.

- New GensUI C++ class, which replaces the old ui-common.c and
  ui-common_gtk.c files.

- Minizip has been upgraded to the latest version (v1.01e) and is now in
  a separate subdirectory in src/.

================================================================

What's new in Gens for Linux v2.15.2/GS-m3?

Milestone 3 introduces the following new features:

- Completely rewritten video rendering subsystem. The new video rendering
  subsystem abstracts the differences between plain SDL and SDL+OpenGL
  and presents a standard interface to the rest of Gens. This will make
  it easier to add in DirectDraw support later on.

- The configuration file handler has been rewritten such that it no longer
  fails to read or write certain configuration entries. Additionally,
  section names and key names are now case-insensitive.

- The OpenGL renderer now supports 15-bit and 32-bit color modes.

- Improved Fast Blur function, written in C, that supports 15, 16, and 32-bit
  color modes. The old Fast Blur function is still used for 15 and 16-bit color
  if x86 asm is enabled via --enable-x86-asm in the ./configure script.

- 7z archives can now be used via an external 7z binary. You must have
  p7zip installed in order to use this feature.

- SegaCD LED code has been updated to work correctly in all color modes.

Milestone 3 fixes the following bugs:

- The built-in debugger now properly updates the screen in 32-bit color.

- Horizontal positioning for 256x224 video modes in 32-bit color was off
  by 32 pixels.

Milestone 3 has the following low-level code changes:

- Standard controller I/O functionality has been ported to C. Additionally,
  controller button presses are now stored in bitfields rather than reserving
  an entire 32-bit int per button. Unfortunately, I could not figure out how
  to port over the TeamPlayer code correctly, so that remains in x86 asm for
  now, with compatibility wrappers with regards to the button format.

- Compression handlers have been rewritten using C++ classes.

- C++ code has been introduced into the Gens/GS codebase. With this change,
  all header files have been updated to include "#ifdef __cplusplus"
  barriers, so older C-only code will link correctly.

================================================================

What's new in Gens for Linux v2.15.2/GS-m2.2?

Milestone 2.2 fixes the following bugs:

- Fixed several bugs with savestate support, including matching struct alignment
  with Gens/Rerecording (Win32) and incorrectly reading x86 memory pointers
  for the emulated Z80 CPU. Please note that savestates from previous versions
  of Gens/GS will not work correctly on m2.2; however, you can load the
  savestates in another emulator, such as the original Gens, and resave it in
  the older format. The older format savestate will then work on Gens/GS.

- CD-ROM drive support is now conditional via the ./configure script.

- 32-bit color now works for 32X games.

================================================================

What's new in Gens for Linux v2.15.2/GS-m2.1?

Milestone 2.1 fixes the following bugs:

- 32X VDP rendering was accidentally broken completely in m2. It's fixed
  now, at least for 15-bit and 16-bit color. 32-bit color mode still needs
  to be fixed.

- The window title for 32X games was always set to "32X (PAL)", even if
  the game is NTSC. This is fixed.

================================================================

What's new in Gens for Linux v2.15.2/GS-m2?

Milestone 2 introduces the following new features:

- PNG screenshot support via libpng. This was apparently a wishlist item
  for Gens for the past several years, but no one bothered to add it.

- Screenshots now save the unfiltered image at the correct resolution.
  For example, Sonic CD special stages now save as a 256x224 image.

- Rewrite of the way compressed files are handled. Compressed files are
  now handled using a generic COMPRESS_Handler interface. Currently, only
  GZip and Zip files are supported (the same as before), but it's now
  much easier and simpler to add new formats.

- The new compression handler detects compressed files by checking the
  file's header instead of relying on the file's extension. This may help
  in cases where a file is misnamed.

- Multi-file Zip support. If a Zip file containing multiple files is
  selected, Gens will prompt you to select which file to open. The UI
  for selecting a file is currently not polished, but it will be improved
  later on.

- Rewrite of the way renderers are handled. The new rendering system uses
  the same rendering code, but has a much simpler calling interface.

- Initial 32-bit color support, ported from Gens Rerecording. Most of the
  32-bit color renderers haven't been ported from Gens Rerecording yet,
  so only three are available in 32-bit: Normal, Double, and Scale2x.
  15-bit or 16-bit color is necessary for the others. To change color modes,
  select Graphics, Bits Per Pixel, and the appropriate color mode.

- Conditional compilation support for OpenGL, PNG, and x86 asm renderers.
  If PNG support is not enabled, screenshots will be taken in BMP format.

- Border color emulation. The border color is set to color 0 of palette 0
  from the MD's VDP.

Milestone 2 fixes the following bugs:

- Fixed a bug where the 32X VDP overlay disappeared when Gens was paused via
  the Escape key. The overlay reappeared when Gens was unpaused, though.

================================================================

What's new in Gens for Linux v2.15.2/GS-m1?

Milestone 1 introduces the following new features:

- Massive code cleanup throughout the entire Gens codebase. Many
  functions with duplicated code have been consolidated so that
  the duplicated code is now shared between the functions. Also,
  several large files have been split into smaller files. For instance,
  gens.c has been split into gens.c, g_md.c, g_mcd.c, g_32x.c,
  and g_palette.c.

- Introduction of OS-independent functions, which will allow for the
  integration of the Win32 version of Gens later on, so that one codebase
  can be used to build a Gens executable for either operating system.

- Gens v7 savestate format, ported from Gens Rerecording. This adds,
  among other things, proper Sega CD savestate support.

- Fixed the built-in debugger, which was broken due to changes in
  the way text was written to the emulated screen.

- Added enhanced Sega CD GFX debugging from Gens Rerecording.

- VDP/GFX debugging now outlines the selected palette.

- Initial attempt to consoldidate global variables into structs.
  This will make it easier to figure out where everything is located.

- Complete rewrite of the GTK+ UI. Among other things, the new UI
  has much improved synchronization, so when a menu item is checked,
  it actually means that item is enabled.
  
- Rewrite of the byteswapping functions so that they describe what is
  being swapped (e.g. be16_to_cpu_array()).

- Extra spaces in game names in ROM headers are removed when the
  game name is displayed on Gens' title bar.
  
- Fixed tons of compiler warnings.