         ______   ___    ___
        /\  _  \ /\_ \  /\_ \
        \ \ \L\ \\//\ \ \//\ \      __     __   _ __   ___
         \ \  __ \ \ \ \  \ \ \   /'__`\ /'_ `\/\`'__\/ __`\
          \ \ \/\ \ \_\ \_ \_\ \_/\  __//\ \L\ \ \ \//\ \L\ \
           \ \_\ \_\/\____\/\____\ \____\ \____ \ \_\\ \____/
            \/_/\/_/\/____/\/____/\/____/\/___L\ \/_/ \/___/
                                           /\____/
                                           \_/__/

                    API compatibility information.

             See readme.txt for a more general overview.

# Introduction

Once Allegro 4.0 is released, we plan to maintain backward compatibility at the Application Programming Interface level for the subsequent stable releases of the 4.x series, that is for the releases with an even minor version number. For example, that means you will be able to compile your program written for version 4.0.0 with version 4.0.23 or version 4.2.1 of the library. However, in order to fix some minor inconsistencies of the original 4.0 API, we may make exceptions to the rule and break strict backward compatibility in a few cases. But this is guaranteed to never happen in a stable series for which major and minor version numbers are fixed; in other words, two stable versions that differ from each other only by the revision (3rd) number will be strictly backward compatible.

# Changes between 4.0.x and 4.2.x series

- The 'aspect' parameter of get_camera_matrix() and get_camera_matrix_f() strictly conforms to the documentation; in particular, setting it to 1 instructs the functions to do no scaling. This was not the case before, because the functions multiplied this aspect ratio by 4/3.
- Menus created from a DIALOG array (by using d_menu_proc for the proc pointer) now correctly use the w and h fields as a minimum for their inclusive dimensions (in the same way as all other GUI elements). Before, they would draw the border outside of this dimension (1 pixel overdraw with other GUI elements), and also add an additional 'shadow' to the right and the bottom (2 pixels overdraw with other GUI elements).
- The 'retrace_count' variable and the 'retrace_proc' callback function take into account the refresh rate (if it is known) when the retrace simulator is not installed. This was not the case before, except under Windows.
- The default value for the mouse configuration variable 'emulate_three' has been changed to 'no' in all cases (even if you have a 2-button mouse).
- The COLORCONV_KEEP_TRANS flag strictly conforms to the documentation now. This was not the case before, because it was ignored when loading bitmaps from datafiles. fixup_datafile() was modified to preserve transparency when this flag is set, which was not guaranteed before in rare cases.
- create_sub_bitmap() is now less tolerant about receiving bad arguments. For example, it used to compensate for negative values for the origin and return NULL if the parent bitmap was NULL. These cases are now ASSERTed in the debug version, but unchecked in the release version.
- install_allegro() and allegro_init() now return an error code if unable to initialise a system driver. Previously they would have aborted the program in such cases. Consequently you should check their return values.
- The preprocessor symbol USE_CONSOLE is deprecated. Define instead the symbol ALLEGRO_USE_CONSOLE prior to including Allegro headers in order to set up Allegro for building a console application.
- The constructors of the fix class from integer and floating point values are now explicit.
- All BeOS gfx driver IDs and constants have been replaced by more meaningful ones. You may have to modify your allegro.cfg to reflect the change, or update and recompile your programs if you used BeOS specific gfx drivers.
- The behaviour of the GFX_SAFE driver has changed: it doesn't try to first set up GFX_AUTODETECTed drivers anymore and is now guaranteed to be a windowed driver when the platform has got a windowing system.
- A datafile object returned by load_datafile_object() used not to contain the properties attached to the object. This has been fixed.
- object_message() now takes care of scaring and unscaring the mouse if the message to be sent is MSG_DRAW.
- file_select_ex() now treats '(+)d' as it does for any other attributes in the extension string which is passed to it: only directories are included and, among them, only those with the correct set of attributes.
- d_ctext_proc() now behaves like d_text_proc() and d_rtext_proc(), that is it takes into account the bounding box to calculate the position which the string is centered around. It previously used only the x field. And, as a consequence, gui_ctext_proc is now expected to behave the same.
- dialog_message() now passes user messages to hidden objects.
- set_volume() doesn't use the hardware mixer anymore to alter the global volume. Use set_hardware_volume() instead to get the old behaviour.
- The default sound volume of Allegro was raised, since there no longer is the risk of wrapping with the new mixer. To restore the volume level to that of previous versions, look at the set_volume_per_voice function. Programs already using set_volume_per_voice are not affected.
- The semantics of rest are clarified so rest(0) does yielding when possible.
- The get_align_matrix[_f] functions would return mirrored matrices in some cases, this was fixed.
- In many places 'unsigned long' variables were used to hold memory addresses. These have been changed to use the 'uintptr_t' type instead.
- 15-bit and 16-bit bitmaps used to be arrays of unsigned shorts, and 32-bit bitmaps used to be arrays of unsigned longs. They have been changed to be arrays of 16-bit and 32-bit integers respectively. This makes a difference on platforms where an unsigned long is not 32-bits wide (e.g. some 64-bit platforms).

# Deprecated materials

The following items have been deprecated and the main documentation was purged of any references to them. If you are still using any of those, now might be a good time to get rid of them (within parentheses is the symbol most likely to be a replacement for the obsolete one, if any). However they are still supported for the sake of backwards compatibility, unless you define the symbol ALLEGRO_NO_COMPATIBILITY prior to including Allegro headers.

- clear (clear_bitmap).
- cpu_fpu (cpu_capabilities, in combination with CPU_FPU).
- cpu_mmx (cpu_capabilities, in combination with CPU_MMX).
- cpu_3dnow (cpu_capabilities, in combination with CPU_3DNOW).
- cpu_cpuid (cpu_capabilities, in combination with CPU_ID).
- draw_character (draw_character_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- fadd (fixadd).
- fsub (fixsub).
- fmul (fixmul).
- fdiv (fixdiv).
- fceil (fixceil).
- ffloor (fixfloor).
- fcos (fixcos).
- fsin (fixsin).
- ftan (fixtan).
- facos (fixacos).
- fasin (fixasin).
- fatan (fixatan).
- fatan2 (fixatan2).
- fsqrt (fixsqrt).
- fhypot (fixhypot).
- file_size (file_size_ex)
- file_select (file_select_ex, passing the two constants OLD_FILESEL_WIDTH and OLD_FILESEL_HEIGHT if you want the file selector to be displayed with the dimensions of the old file selector).
- fix_filename_path (canonicalize_filename).
- for_each_file (for_each_file_ex).
- gui_textout (gui_textout_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- initialise_joystick (install_joystick).
- joy_x (joy).
- joy_y (joy).
- joy_left (joy).
- joy_right (joy).
- joy_up (joy).
- joy_down (joy).
- joy_b1 (joy).
- joy_b2 (joy).
- joy_b3 (joy).
- joy_b4 (joy).
- joy_b5 (joy).
- joy_b6 (joy).
- joy_b7 (joy).
- joy_b8 (joy).
- joy2_x (joy).
- joy2_y (joy).
- joy2_left (joy).
- joy2_right (joy).
- joy2_up (joy).
- joy2_down (joy).
- joy2_b1 (joy).
- joy2_b2 (joy).
- joy_throttle (joy).
- joy_hat (joy).
- JOY_HAT_CENTER.
- JOY_HAT_CENTRE.
- JOY_HAT_LEFT.
- JOY_HAT_RIGHT.
- JOY_HAT_DOWN.
- JOY_HAT_UP.
- KB_EXTENDED.
- KB_NORMAL.
- SEND_MESSAGE (object_message).
- set_window_close_button.
- set_window_close_hook (set_close_button_callback).
- text_mode.
- textout (textout_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textout_centre (textout_centre_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textout_right (textout_right_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textout_justify (textout_justify_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textprintf (textprintf_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textprintf_centre (textprintf_centre_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textprintf_right (textprintf_right_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- textprintf_justify (textprintf_justify_ex, passing the mode you would have passed to text_mode() as the 'bg' parameter).
- PALLETE (PALETTE).
- DAT_PALLETE (DAT_PALETTE).
- black_pallete (black_palette).
- desktop_pallete (desktop_palette)
- get_pallete (get_palette).
- set_pallete (set_palette).
- get_pallete_range (get_palette_range)
- set_pallete_range (set_palette_range).
- fli_pallete (fli_palette).
- pallete_color (palette_color).
- select_pallete (select_palette).
- set_clip (set_clip_rect).
- unselect_pallete (unselect_palette).
- generate_332_pallete (generate_332_palette).
- generate_optimized_pallete (generate_optimized_palette).
- yield_timeslice (rest, passing 0 as parameter)
- retrace_proc (retrace_count or install_int).
- timer_can_simulate_retrace.
- timer_is_using_retrace.
- timer_simulate_retrace (when enable_triple_buffer is called, the mode-X driver still enables retrace simulation automatically where possible).
- split_modex_screen.