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/*!
@page quick Getting started — A quick introduction
@page quick Getting started
@tableofcontents
This guide will show how to write simple OpenGL applications using GLFW 3. It
will introduce a few of the most commonly used functions, but there are many
others. To see detailed documentation on any GLFW function, just click on its
name.
This guide takes you through writing a simple application using GLFW 3. The
application will create a window and OpenGL context, render a rotating triangle
and exit when the user closes the window or presses Escape. This guide will
introduce a few of the most commonly used functions, but there are many more.
This guide assumes no experience with earlier versions of GLFW. If you
have used GLFW 2.x in the past, you should also read the
[transition guide](@ref moving).
have used GLFW 2 in the past, read the @ref moving guide, as some functions
behave differently in GLFW 3.
@section quick_include Including the GLFW header
@section quick_steps Step by step
In the files of your program where you use OpenGL or GLFW, you need to include
the GLFW 3 header file.
@subsection quick_include Including the GLFW header
In the source files of your application where you use OpenGL or GLFW, you need
to include the GLFW 3 header file.
@code
#include <GLFW/glfw3.h>
@@ -54,40 +56,39 @@ inclusion of the GLFW header.
@endcode
@section quick_init_term Initializing and terminating GLFW
@subsection quick_init_term Initializing and terminating GLFW
Before you can use most GLFW functions, the library must be initialized. This
is done with @ref glfwInit, which returns non-zero if successful, or zero if an
error occurred.
Before you can use most GLFW functions, the library must be initialized. On
successful initialization, non-zero is returned. If an error occurred, zero is
returned.
@code
if (!glfwInit())
exit(EXIT_FAILURE);
@endcode
When you are done using GLFW, typically at the very end of the program, you need
to call @ref glfwTerminate.
When you are done using GLFW, typically just before the application exits, you
need to terminate GLFW.
@code
glfwTerminate();
@endcode
This destroys any remaining windows and releases any other resources allocated by
GLFW. After this call, you must call @ref glfwInit again before using any GLFW
GLFW. After this call, you must initialize GLFW again before using any GLFW
functions that require it.
@section quick_capture_error Setting an error callback
@subsection quick_capture_error Setting an error callback
Most events are reported through callbacks, whether it's a key being pressed,
a GLFW window being moved, or an error occurring. Callbacks are simply
C functions (or C++ static methods) that are called by GLFW with arguments
describing the event.
In case @ref glfwInit or any other GLFW function fails, an error is reported to
the GLFW error callback. You can receive these reports by setting the error
callback. The callback function itself should match the signature of @ref
GLFWerrorfun. Here is a simple error callback that just prints the error
In case a GLFW function fails, an error is reported to the GLFW error callback.
You can receive these reports with an error callback. This function must have
the signature below. This simple error callback just prints the error
description to `stderr`.
@code
@@ -97,28 +98,28 @@ void error_callback(int error, const char* description)
}
@endcode
Setting the callback, so GLFW knows to call it, is done with @ref
glfwSetErrorCallback. This is one of the few GLFW functions that may be called
before @ref glfwInit, which lets you be notified of errors during
initialization, so you should set it before you do anything else with GLFW.
Callback functions must be set, so GLFW knows to call them. The function to set
the error callback is one of the few GLFW functions that may be called before
initialization, which lets you be notified of errors both during and after
initialization.
@code
glfwSetErrorCallback(error_callback);
@endcode
@section quick_create_window Creating a window and context
@subsection quick_create_window Creating a window and context
The window (and its context) is created with @ref glfwCreateWindow, which
returns a handle to the created window. For example, this creates a 640 by 480
windowed mode window:
The window and its OpenGL context are created with a single call, which returns
a handle to the created combined window and context object. For example, this
creates a 640 by 480 windowed mode window with an OpenGL context:
@code
GLFWwindow* window = glfwCreateWindow(640, 480, "My Title", NULL, NULL);
@endcode
If window creation fails, `NULL` will be returned, so you need to check whether
it did.
If window or context creation fails, `NULL` will be returned, so it is necessary
to check the return value.
@code
if (!window)
@@ -128,24 +129,11 @@ if (!window)
}
@endcode
This handle is then passed to all window related functions, and is provided to
you along with input events, so you know which window received the input.
The window handle is passed to all window related functions and is provided to
along to all window related callbacks, so they can tell which window received
the event.
To create a full screen window, you need to specify which monitor the window
should use. In most cases, the user's primary monitor is a good choice. You
can get this with @ref glfwGetPrimaryMonitor. To make the above window
full screen, just pass along the monitor handle:
@code
GLFWwindow* window = glfwCreateWindow(640, 480, "My Title", glfwGetPrimaryMonitor(), NULL);
@endcode
Full screen windows cover the entire display area of a monitor, have no border
or decorations, and change the monitor's resolution to the one most closely
matching the requested window size.
When you are done with the window, destroy it with the @ref glfwDestroyWindow
function.
When a window is no longer needed, destroy it.
@code
glfwDestroyWindow(window);
@@ -155,22 +143,22 @@ Once this function is called, no more events will be delivered for that window
and its handle becomes invalid.
@section quick_context_current Making the OpenGL context current
@subsection quick_context_current Making the OpenGL context current
Before you can use the OpenGL API, it must have a current OpenGL context. You
make a window's context current with @ref glfwMakeContextCurrent. It will then
remain as the current context until you make another context current or until
the window owning it is destroyed.
make a window's context current.
@code
glfwMakeContextCurrent(window);
@endcode
The context will then remain as current until you make another context current
or until the window owning the current context is destroyed.
@section quick_window_close Checking the window close flag
Each window has a flag indicating whether the window should be closed. This can
be checked with @ref glfwWindowShouldClose.
@subsection quick_window_close Checking the window close flag
Each window has a flag indicating whether the window should be closed.
When the user attempts to close the window, either by pressing the close widget
in the title bar or using a key combination like Alt+F4, this flag is set to 1.
@@ -194,11 +182,11 @@ useful if you want to interpret other kinds of input as closing the window, like
for example pressing the escape key.
@section quick_key_input Receiving input events
@subsection quick_key_input Receiving input events
Each window has a large number of callbacks that can be set to receive all the
various kinds of events. To receive key press and release events, a
[key callback](@ref GLFWkeyfun) is set using @ref glfwSetKeyCallback.
various kinds of events. To receive key press and release events, create a key
callback function.
@code
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
@@ -208,16 +196,21 @@ static void key_callback(GLFWwindow* window, int key, int scancode, int action,
}
@endcode
For event callbacks to actually be called when an event occurs, you need to
process events as described below.
The key callback, like other window related callbacks, are set per-window.
@code
glfwSetKeyCallback(window, key_callback);
@endcode
In order for event callbacks to be called when events occur, you need to process
events as described below.
@section quick_render Rendering with OpenGL
@subsection quick_render Rendering with OpenGL
Once you have a current OpenGL context, you can use OpenGL normally. In this
tutorial, a multi-colored rotating triangle will be rendered. The framebuffer
size, needed by this example for `glViewport` and `glOrtho`, is retrieved with
@ref glfwGetFramebufferSize.
size needs to be retrieved for `glViewport`.
@code
int width, height;
@@ -225,72 +218,80 @@ glfwGetFramebufferSize(window, &width, &height);
glViewport(0, 0, width, height);
@endcode
However, you can also set a framebuffer size callback using @ref
You can also set a framebuffer size callback using @ref
glfwSetFramebufferSizeCallback and call `glViewport` from there.
@code
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
@endcode
@subsection quick_timer Reading the timer
@section quick_timer Reading the timer
For the triangle to rotate properly, a time source is needed. GLFW provides
@ref glfwGetTime, which returns the number of seconds since @ref glfwInit as
a `double`. The time source used is the most accurate on each platform and
generally has micro- or nanosecond resolution.
To create smooth animation, a time source is needed. GLFW provides a timer that
returns the number of seconds since initialization. The time source used is the
most accurate on each platform and generally has micro- or nanosecond
resolution.
@code
double time = glfwGetTime();
@endcode
@section quick_swap_buffers Swapping buffers
@subsection quick_swap_buffers Swapping buffers
GLFW windows by default use double buffering. That means that you have two
rendering buffers; a front buffer and a back buffer. The front buffer is the
one being displayed and the back buffer the one you render to.
GLFW windows by default use double buffering. That means that each window has
two rendering buffers; a front buffer and a back buffer. The front buffer is
the one being displayed and the back buffer the one you render to.
When the entire frame has been rendered, it is time to swap the back and the
front buffers in order to display the rendered frame, and begin rendering a new
frame. This is done with @ref glfwSwapBuffers.
When the entire frame has been rendered, the buffers need to be swapped with one
another, so the back buffer becomes the front buffer and vice versa.
@code
glfwSwapBuffers(window);
@endcode
The swap interval indicates how many frames to wait until swapping the buffers,
commonly known as *vsync*. By default, the swap interval is zero, meaning
buffer swapping will occur immediately. On fast machines, many of those frames
will never be seen, as the screen is still only updated typically 60-75 times
per second, so this wastes a lot of CPU and GPU cycles.
@section quick_process_events Processing events
Also, because the buffers will be swapped in the middle the screen update,
leading to [screen tearing](https://en.wikipedia.org/wiki/Screen_tearing).
For these reasons, applications will typically want to set the swap interval to
one. It can be set to higher values, but this is usually not recommended,
because of the input latency it leads to.
@code
glfwSwapInterval(1);
@endcode
This function acts on the current context and will fail unless a context is
current.
@subsection quick_process_events Processing events
GLFW needs to communicate regularly with the window system both in order to
receive events and to show that it hasn't locked up. Event processing must be
done regularly and is normally done each frame before rendering but after buffer
swap.
receive events and to show that the application hasn't locked up. Event
processing must be done regularly while you have visible windows and is normally
done each frame after buffer swapping.
There are two ways to process pending events. @ref glfwPollEvents processes
only those events that have already been received and then returns immediately.
This is the best choice when rendering continually, like most games do.
There are two methods for processing pending events; polling and waiting. This
example will use event polling, which processes only those events that have
already been received and then returns immediately.
@code
glfwPollEvents();
@endcode
If instead you only need to update your rendering once you have received new
input, @ref glfwWaitEvents is a better choice. It waits until at least one
event has been received, putting the thread to sleep in the meantime, and then
processes all received events just like @ref glfwPollEvents does. This saves
a great deal of CPU cycles and is useful for, for example, many kinds of editing
tools.
@code
glfwWaitEvents();
@endcode
This is the best choice when rendering continually, like most games do. If
instead you only need to update your rendering once you have received new input,
@ref glfwWaitEvents is a better choice. It waits until at least one event has
been received, putting the thread to sleep in the meantime, and then processes
all received events. This saves a great deal of CPU cycles and is useful for,
for example, many kinds of editing tools.
@section quick_example Putting it together: A simple application
@section quick_example Putting it together
Now that you know how to initialize GLFW, create a window and poll for
keyboard input, it's possible to create a simple program.