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#include <epoxy/gl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "client.h"
#include "gl.h"
#include "log.h"
#define max(a, b) ((a) > (b) ? (a) : (b))
static void load_shader(GLuint shader, const char *filename);
static GLuint create_shader_program(const char *vert, const char *frag);
void gl_initialise(struct client_state *state)
{
if (state->window.background_image.buffer == NULL) {
return;
}
struct gl *gl = &state->window.surface.gl;
/* Compile and link the shader programs */
gl->shader = create_shader_program(
SHADER_PATH "vert.vert",
SHADER_PATH "frag.frag"
);
glUseProgram(gl->shader);
glUniform1i(glGetUniformLocation(gl->shader, "tex"), 0);
/* Create a vertex buffer for a quad filling the screen */
float vertices[] = {
// Position Texcoords
-1.0f, 1.0f, 0.0f, 0.0f, // Top-left
1.0f, 1.0f, 1.0f, 0.0f, // Top-right
1.0f, -1.0f, 1.0f, 1.0f, // Bottom-right
-1.0f, -1.0f, 0.0f, 1.0f // Bottom-left
};
glGenBuffers(1, &gl->vbo);
glBindBuffer(GL_ARRAY_BUFFER, gl->vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
/* Create a vertex array and enable vertex attributes for the shaders. */
glGenVertexArrays(1, &gl->vao);
glBindVertexArray(gl->vao);
GLint posAttrib = glGetAttribLocation(gl->shader, "position");
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 4*sizeof(float), 0);
glEnableVertexAttribArray(posAttrib);
GLint texAttrib = glGetAttribLocation(gl->shader, "texcoord");
glVertexAttribPointer(texAttrib, 2, GL_FLOAT, GL_FALSE, 4*sizeof(float), (void *)(2*sizeof(float)));
glEnableVertexAttribArray(texAttrib);
glBindVertexArray(0);
/* Create the element buffer object that will actually be drawn via
* glDrawElements(). */
GLuint elements[] = {
0, 1, 2,
2, 3, 0
};
glGenBuffers(1, &gl->ebo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, gl->ebo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
/* Create the texture we'll draw to */
glGenTextures(1, &gl->texture);
glBindTexture(GL_TEXTURE_2D, gl->texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, state->window.background_image.width, state->window.background_image.height, 0, GL_RGBA,
GL_UNSIGNED_BYTE, (GLvoid *)state->window.background_image.buffer);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
/* Bind the actual bits we'll be using to render */
glBindVertexArray(gl->vao);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, gl->ebo);
}
void gl_draw(struct client_state *state)
{
glClearColor(
state->window.background_color.r,
state->window.background_color.g,
state->window.background_color.b,
state->window.background_color.a
);
glClear(GL_COLOR_BUFFER_BIT);
if (state->window.background_image.buffer == NULL) {
return;
}
double scale = max(
(double)state->window.surface.width / state->window.background_image.width,
(double)state->window.surface.height / state->window.background_image.height
);
uint32_t width = (uint32_t)(scale * state->window.background_image.width);
uint32_t height = (uint32_t)(scale * state->window.background_image.height);
int32_t x = -((int32_t)width - (int32_t)state->window.surface.width) / 2;
int32_t y = -((int32_t)height - (int32_t)state->window.surface.height) / 2;
glViewport(x, y, width, height);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
}
void load_shader(GLuint shader, const char *filename)
{
errno = 0;
FILE *fp = fopen(filename, "rb");
if (!fp) {
log_error("Failed to load shader %s: %s.\n", filename, strerror(errno));
exit(EXIT_FAILURE);
}
if (fseek(fp, 0, SEEK_END) != 0) {
log_error("Failed to load shader %s: %s.\n", filename, strerror(errno));
fclose(fp);
exit(EXIT_FAILURE);
}
long size = ftell(fp);
if (size <= 0) {
log_error("Failed to load shader %s: %s.\n", filename, strerror(errno));
fclose(fp);
exit(EXIT_FAILURE);
}
unsigned long usize = (unsigned long) size;
GLchar *source = malloc(usize + 1);
rewind(fp);
if (fread(source, 1, usize, fp) != usize) {
log_error("Failed to load shader %s: %s.\n", filename, strerror(errno));
fclose(fp);
exit(EXIT_FAILURE);
}
fclose(fp);
source[usize] = '\0';
glShaderSource(shader, 1, (const GLchar *const *)&source, NULL);
free(source);
glCompileShader(shader);
GLint status;
glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
if (status != GL_TRUE) {
log_error("Failed to compile shader %s!\n", filename);
GLint info_length = 0;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &info_length);
if (info_length > 1) {
char *log = malloc((unsigned)info_length * sizeof(*log));
glGetShaderInfoLog(shader, info_length, NULL, log);
log_error("\t%s\n", log);
free(log);
}
exit(EXIT_FAILURE);
}
}
GLuint create_shader_program(const char *vert, const char *frag)
{
GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
load_shader(vertex_shader, vert);
GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
load_shader(fragment_shader, frag);
GLuint shader = glCreateProgram();
glAttachShader(shader, vertex_shader);
glAttachShader(shader, fragment_shader);
glLinkProgram(shader);
return shader;
}
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