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tearing.c
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tearing.c
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//========================================================================
// Vsync enabling test
// Copyright (c) Camilla Berglund <elmindreda@elmindreda.org>
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software. If you use this software
// in a product, an acknowledgment in the product documentation would
// be appreciated but is not required.
//
// 2. Altered source versions must be plainly marked as such, and must not
// be misrepresented as being the original software.
//
// 3. This notice may not be removed or altered from any source
// distribution.
//
//========================================================================
//
// This test renders a high contrast, horizontally moving bar, allowing for
// visual verification of whether the set swap interval is indeed obeyed
//
//========================================================================
#include <GLFW/glfw3.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
static int swap_interval;
static double frame_rate;
static void update_window_title(GLFWwindow* window)
{
char title[256];
sprintf(title, "Tearing detector (interval %i, %0.1f Hz)",
swap_interval, frame_rate);
glfwSetWindowTitle(window, title);
}
static void set_swap_interval(GLFWwindow* window, int interval)
{
swap_interval = interval;
glfwSwapInterval(swap_interval);
update_window_title(window);
}
static void error_callback(int error, const char* description)
{
fprintf(stderr, "Error: %s\n", description);
}
static void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_SPACE && action == GLFW_PRESS)
set_swap_interval(window, 1 - swap_interval);
}
int main(void)
{
float position;
unsigned long frame_count = 0;
double last_time, current_time;
GLFWwindow* window;
glfwSetErrorCallback(error_callback);
if (!glfwInit())
exit(EXIT_FAILURE);
window = glfwCreateWindow(640, 480, "", NULL, NULL);
if (!window)
{
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwMakeContextCurrent(window);
set_swap_interval(window, 0);
last_time = glfwGetTime();
frame_rate = 0.0;
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
glfwSetKeyCallback(window, key_callback);
glMatrixMode(GL_PROJECTION);
glOrtho(-1.f, 1.f, -1.f, 1.f, 1.f, -1.f);
glMatrixMode(GL_MODELVIEW);
while (!glfwWindowShouldClose(window))
{
glClear(GL_COLOR_BUFFER_BIT);
position = cosf((float) glfwGetTime() * 4.f) * 0.75f;
glRectf(position - 0.25f, -1.f, position + 0.25f, 1.f);
glfwSwapBuffers(window);
glfwPollEvents();
frame_count++;
current_time = glfwGetTime();
if (current_time - last_time > 1.0)
{
frame_rate = frame_count / (current_time - last_time);
frame_count = 0;
last_time = current_time;
update_window_title(window);
}
}
glfwTerminate();
exit(EXIT_SUCCESS);
}

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tearing.c (3 KB)

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