glfw/docs/moving.dox

/*!

@page moving Moving from GLFW 2 to 3

@tableofcontents

This is a transition guide for moving from GLFW 2 to 3.  It describes what has
changed or been removed, but does *not* include
[new features](@ref news) unless they are required when moving an existing code
base onto the new API.  For example, use of the new multi-monitor functions are
required to create full screen windows with GLFW 3.


@section moving_removed Removed features

@subsection moving_threads Threading functions

The threading functions have been removed, including the sleep function.  They
were fairly primitive, under-used, poorly integrated and took time away from the
focus of GLFW (i.e.  context, input and window).  There are better threading
libraries available and native threading support is available in both C++11 and
C11, both of which are gaining traction. 

If you wish to use the C++11 or C11 facilities but your compiler doesn't yet
support them, see the
[TinyThread++](https://gitorious.org/tinythread/tinythreadpp) and
[TinyCThread](https://gitorious.org/tinythread/tinycthread) projects created by
the original author of GLFW.  These libraries implement a usable subset of the
threading APIs in C++11 and C11, and in fact some GLFW 3 test programs use
TinyCThread.

However, GLFW 3 has better support for *use from multiple threads* than GLFW
2 had.  Contexts can be made current on and rendered with from secondary
threads, and the documentation explicitly states which functions may be used
from secondary threads and which may only be used from the main thread, i.e. the
thread that calls main.


@subsection moving_image Image and texture loading

The image and texture loading functions have been removed.  They only supported
the Targa image format, making them mostly useful for beginner level examples.
To become of sufficiently high quality to warrant keeping them in GLFW 3, they
would need not only to support other formats, but also modern extensions to the
OpenGL texturing facilities.  This would either add a number of external
dependencies (libjpeg, libpng, etc.), or force GLFW to ship with inline versions
of these libraries. 

As there already are libraries doing this, it seems unnecessary both to
duplicate this work and to tie this duplicate to GLFW.  Projects similar to
GLFW, such as freeglut, could also gain from such a library.  Also, would be no
platform-specific part of such a library, as both OpenGL and stdio are available
wherever GLFW is.


@subsection moving_char_up Character actions

The action parameter of the [character callback](@ref GLFWcharfun) has been
removed.  This was an artefact of the origin of GLFW, i.e. being developed in
English by a Swede.  However, many keyboard layouts require more than one key to
produce characters with diacritical marks. Even the Swedish keyboard layout
requires this for uncommon cases like ü.

Note that this is only the removal of the *action parameter* of the character
callback, *not* the removal of the character callback itself. 


@subsection moving_wheel Mouse wheel position

The `glfwGetMouseWheel` function has been removed.  Scroll events do not
represent an absolute state, but is instead an interpretation of a relative
change in state, like character input.  So, like character input, there is no
sane 'current state' to return.  The mouse wheel callback has been replaced by
a [scroll callback](@ref GLFWscrollfun) that receives two-dimensional scroll
offsets.


@subsection moving_stdcall GLFWCALL macro

The `GLFWCALL` macro, which made callback functions use
[__stdcall](http://msdn.microsoft.com/en-us/library/zxk0tw93.aspx) on Windows,
has been removed.  GLFW is written in C, not Pascal.  Removing this macro means
there's one less thing for users of GLFW to remember, i.e. the requirement to
mark all callback functions with `GLFWCALL`.  It also simplifies the creation of
DLLs and DLL link libraries, as there's no need to explicitly disable `@n` entry
point suffixes. 


@subsection moving_mbcs Win32 MBCS support

The Win32 port of GLFW 3 will not compile in
[MBCS mode](http://msdn.microsoft.com/en-us/library/5z097dxa.aspx).
However, because the use of the Unicode version of the Win32 API doesn't affect
the process as a whole, but only those windows created using it, it's perfectly
possible to call MBCS functions from other parts of the same application.
Therefore, even if an application using GLFW has MBCS mode code, there's no need
for GLFW itself to support it.


@subsection moving_windows Support for versions of Windows older than XP

All explicit support for version of Windows older than XP has been removed.
There is no code that actively prevents GLFW 3 from running on these earlier
versions, but it uses Win32 functions that those versions lack.

Windows XP was released in 2001, and by now (2013) it has not only
replaced almost all earlier versions of Windows, but is itself rapidly being
replaced by Windows 7 and 8.  The MSDN library doesn't even provide
documentation for version older than Windows 2000, making it difficult to
maintain compatibility with these versions even if it was deemed worth the
effort.

The Win32 API has also not stood still, and GLFW 3 uses many functions only
present on Windows XP or later.  Even supporting an OS as new as XP (new
from the perspective of GLFW 2, which still supports Windows 95) requires
runtime checking for a number of functions that are present only on modern
version of Windows.


@subsection moving_syskeys Capture of system-wide hotkeys

The ability to disable and capture system-wide hotkeys like Alt+Tab has been
removed.  Modern applications, whether they're games, scientific visualisations
or something else, are nowadays expected to be good desktop citizens and allow
these hotkeys to function even when running in full screen mode.


@subsection moving_opened Window open parameter

The `GLFW_OPENED` window parameter has been removed.  As long as the
[window object](@ref window_object) is around, the window is "open".  To detect
when the user attempts to close the window, see @ref glfwWindowShouldClose and
the [close callback](@ref GLFWwindowclosefun).


@subsection moving_autopoll Automatic polling of events

GLFW 3 does not automatically poll for events on @ref glfwSwapBuffers, which
means you need to call @ref glfwPollEvents or @ref glfwWaitEvents yourself.
Unlike buffer swap, the event processing functions act on all windows at once.


@subsection moving_terminate Automatic termination

GLFW 3 does not register @ref glfwTerminate with `atexit` at initialization.  To
properly release all resources allocated by GLFW, you should therefore call @ref
glfwTerminate yourself before exiting.


@subsection moving_glu GLU header inclusion

GLFW 3 does not include the GLU header by default and GLU itself has been
deprecated, but you can request that the GLFW 3 header includes it by defining
`GLFW_INCLUDE_GLU` before the inclusion of the GLFW 3 header.


@section moving_changed Changes to existing features

@subsection moving_window_handles Window handles

Because GLFW 3 supports multiple windows, window handle parameters have been
added to all window-related GLFW functions and callbacks.  The handle of
a newly created window is returned by @ref glfwCreateWindow (formerly
`glfwOpenWindow`).  Window handles are of the `GLFWwindow*` type, i.e. a pointer
to an opaque struct.


@subsection moving_monitor Multi-monitor support

GLFW 3 provides support for multiple monitors, adding the `GLFWmonitor*` handle
type and a set of related functions.  To request a full screen mode window,
instead of passing `GLFW_FULLSCREEN` you specify which monitor you wish the
window to use.  There is @ref glfwGetPrimaryMonitor that provides behaviour
similar to that of GLFW 2.


@subsection moving_hidpi Separation of window and framebuffer sizes

Window positions and sizes now use screen coordinates, which may not be the same
as pixels on machines with high-DPI monitors.  This is important as OpenGL uses
pixels, not screen coordinates.  Most commonly, the rectangle specified with
`glViewport` needs to use pixels.  Therefore, framebuffer size functions have
been added.  You can retrieve the size of the framebuffer of a window with @ref
glfwGetFramebufferSize function.  A framebuffer size callback has been added,
which can be set with @ref glfwSetFramebufferSizeCallback.


@subsection moving_window_close Window closing

Window closing initiated by the user is now just an event like any other.
Unlike GLFW 2, windows and contexts created with GLFW 3 will not disappear from
underfoot.  Each window now has a close flag, which is set when the user
attempts to close it.  By default, nothing else happens and the window stays
open and visible.  It is then up to you to either destroy the window, take some
other action or simply ignore the request.  You can query the close flag at any
time with @ref glfwWindowShouldClose and set it at any time with @ref
glfwSetWindowShouldClose.

The close callback no longer returns a value.  Instead, it is called after the
close flag has been set so it can override its value, if it chooses to, before
event processing completes.  You may however not call @ref glfwDestroyWindow
from the close callback (or any other window related callback).

GLFW itself never clears the close flag, allowing you to set it for other
reasons for the window to close as well, for example the user choosing Quit from
the main menu.


@subsection moving_context Explicit context management

Each GLFW 3 window has its own OpenGL context and only you, the user, can know
which context should be current on which thread at any given time.  Therefore,
GLFW 3 makes no assumptions about when you want a certain context to be current,
leaving that decision to you.

This means, among other things, that you need to call @ref
glfwMakeContextCurrent after creating a window before you can call any OpenGL
functions.


@subsection moving_repeat Key repeat

The `GLFW_KEY_REPEAT` enable has been removed and key repeat is always enabled
for both keys and characters.  A new key action, `GLFW_REPEAT`, has been added
to allow the [key callback](@ref GLFWkeyfun) to distinguish an initial key press
from a repeat.  Note that @ref glfwGetKey still returns only `GLFW_PRESS` or
`GLFW_RELEASE`.


@subsection moving_keys Physical key input

GLFW 3 key tokens map to physical keys, unlike in GLFW 2 where they mapped to
the values generated by the current keyboard layout.  The tokens are named
according to the values they would have using the standard US layout, but this
is only a convenience, as most programmers are assumed to know that layout.
This means that (for example) `GLFW_KEY_LEFT_BRACKET` is always a single key and
is the same key in the same place regardless of what keyboard layouts the users
of your program has.

The key input facility was never meant for text input, although using it that
way worked slightly better in GLFW 2.  If you were using it to input text, you
should be using the character callback instead, on both GLFW 2 and 3.  This will
give you the characters being input, as opposed to the keys being pressed.

GLFW 3 has key tokens for all keys on a standard 105 key keyboard, so instead of
having to remember whether to check for `'a'` or `'A'`, you now check for
`GLFW_KEY_A`.


@subsection moving_joystick Joystick input

The `glfwGetJoystickPos` function has been renamed to @ref glfwGetJoystickAxes.

The `glfwGetJoystickParam` function and the `GLFW_PRESENT`, `GLFW_AXES` and
`GLFW_BUTTONS` tokens have been replaced by the @ref glfwJoystickPresent
function as well as axis and button counts returned by the @ref
glfwGetJoystickAxes and @ref glfwGetJoystickButtons functions.


@subsection moving_video_modes Video mode enumeration

Video mode enumeration is now per-monitor.  The @ref glfwGetVideoModes function
now returns all available modes for a specific monitor instead of requiring you
to guess how large an array you need.  The `glfwGetDesktopMode` function, which
had poorly defined behavior, has been replaced by @ref glfwGetVideoMode, which
returns the current mode of a monitor.


@subsection moving_cursor Cursor positioning

GLFW 3 only allows you to position the cursor within a window using @ref
glfwSetCursorPos (formerly `glfwSetMousePos`) when that window is active.
Unless the window is active, the function fails silently.


@subsection moving_hints Persistent window hints

Window hints are no longer reset to their default values on window creation, but
instead retain their values until modified by @ref glfwWindowHint (formerly
`glfwOpenWindowHint`) or @ref glfwDefaultWindowHints, or until the library is
terminated and re-initialized.


@section moving_renamed Name changes

@subsection moving_renamed_files Library and header file

The GLFW 3 header is named @ref glfw3.h and moved to the `GLFW` directory, to
avoid collisions with the headers of other major versions.  Similarly, the GLFW
3 library is named `glfw3,` except when it's installed as a shared library on
Unix-like systems, where it uses the
[soname](https://en.wikipedia.org/wiki/soname) `libglfw.so.3`.


@subsection moving_renamed_functions Functions

| GLFW 2                      | GLFW 3                        | Notes |
| --------------------------- | ----------------------------- | ----- |
| `glfwOpenWindow`            | @ref glfwCreateWindow         | All channel bit depths are now hints
| `glfwCloseWindow`           | @ref glfwDestroyWindow        |       |
| `glfwOpenWindowHint`        | @ref glfwWindowHint           | Now accepts all `GLFW_*_BITS` tokens |
| `glfwEnable`                | @ref glfwSetInputMode         |       |
| `glfwDisable`               | @ref glfwSetInputMode         |       |
| `glfwGetMousePos`           | @ref glfwGetCursorPos         |       |
| `glfwSetMousePos`           | @ref glfwSetCursorPos         |       |
| `glfwSetMousePosCallback`   | @ref glfwSetCursorPosCallback |       |
| `glfwSetMouseWheelCallback` | @ref glfwSetScrollCallback    | Accepts two-dimensional scroll offsets as doubles |
| `glfwGetJoystickPos`        | @ref glfwGetJoystickAxes      |       |
| `glfwGetWindowParam`        | @ref glfwGetWindowAttrib      |       |
| `glfwGetGLVersion`          | @ref glfwGetWindowAttrib      | Use `GLFW_CONTEXT_VERSION_MAJOR`, `GLFW_CONTEXT_VERSION_MINOR` and `GLFW_CONTEXT_REVISION` |
| `glfwGetDesktopMode`        | @ref glfwGetVideoMode         | Returns the current mode of a monitor |
| `glfwGetJoystickParam`      | @ref glfwJoystickPresent      | The axis and button counts are provided by @ref glfwGetJoystickAxes and @ref glfwGetJoystickButtons |

@subsection moving_renamed_tokens Tokens

| GLFW 2                      | GLFW 3                       | Notes |
| --------------------------- | ---------------------------- | ----- |
| `GLFW_OPENGL_VERSION_MAJOR` | `GLFW_CONTEXT_VERSION_MAJOR` | Renamed as it applies to OpenGL ES as well |
| `GLFW_OPENGL_VERSION_MINOR` | `GLFW_CONTEXT_VERSION_MINOR` | Renamed as it applies to OpenGL ES as well |
| `GLFW_FSAA_SAMPLES`         | `GLFW_SAMPLES`               | Renamed to match the OpenGL API |
| `GLFW_ACTIVE`               | `GLFW_FOCUSED`               | Renamed to match the window focus callback |
| `GLFW_WINDOW_NO_RESIZE`     | `GLFW_RESIZABLE`             | The default has been inverted |
| `GLFW_MOUSE_CURSOR`         | `GLFW_CURSOR`                | Used with @ref glfwSetInputMode |
| `GLFW_KEY_ESC`              | `GLFW_KEY_ESCAPE`            |       |
| `GLFW_KEY_DEL`              | `GLFW_KEY_DELETE`            |       |
| `GLFW_KEY_PAGEUP`           | `GLFW_KEY_PAGE_UP`           |       |
| `GLFW_KEY_PAGEDOWN`         | `GLFW_KEY_PAGE_DOWN`         |       |
| `GLFW_KEY_KP_NUM_LOCK`      | `GLFW_KEY_NUM_LOCK`          |       |
| `GLFW_KEY_LCTRL`            | `GLFW_KEY_LEFT_CONTROL`      |       |
| `GLFW_KEY_LSHIFT`           | `GLFW_KEY_LEFT_SHIFT`        |       |
| `GLFW_KEY_LALT`             | `GLFW_KEY_LEFT_ALT`          |       |
| `GLFW_KEY_LSUPER`           | `GLFW_KEY_LEFT_SUPER`        |       |
| `GLFW_KEY_RCTRL`            | `GLFW_KEY_RIGHT_CONTROL`     |       |
| `GLFW_KEY_RSHIFT`           | `GLFW_KEY_RIGHT_SHIFT`       |       |
| `GLFW_KEY_RALT`             | `GLFW_KEY_RIGHT_ALT`         |       |
| `GLFW_KEY_RSUPER`           | `GLFW_KEY_RIGHT_SUPER`       |       |

*/