DashGL

Brickout Invaders Astroids Information
By Kion Nov. 5, 2017
View Source On Github

Now that we can move the player left and right, we will prepare for our program to allow the player to shoot. To start we draw a stationary bullet in the middle of the screen.

#include <stdlib.h>
#include <epoxy/gl.h>
#include <epoxy/glx.h>
#include <gtk/gtk.h>
#include "DashGL/dashgl.h"

static void on_realize(GtkGLArea *area);
static void on_render(GtkGLArea *area, GdkGLContext *context);
static gboolean on_idle(gpointer data);
static gboolean on_keydown(GtkWidget *widget, GdkEventKey *event);
static gboolean on_keyup(GtkWidget *widget, GdkEventKey *event);

#define WIDTH 640.0f
#define HEIGHT 480.0f

GLuint program;
GLuint vao;
GLint attribute_texcoord, attribute_coord2d;
GLint uniform_mytexture, uniform_mvp;

struct {
	GLuint vbo;
	GLuint tex;
	mat4 mvp;
} background;

struct {
	GLuint vbo;
	GLuint tex;
	vec3 pos;
	mat4 mvp;
	gboolean left;
	gboolean right;
	int num_bullets;
	vec3 *bullets;
	gboolean *active;
} player;

struct {
	GLuint vbo;
	GLuint tex;
	mat4 mvp;
} bullet;

int main(int argc, char *argv[]) {

	GtkWidget *window;
	GtkWidget *glArea;

	gtk_init(&argc, &argv);

	// Initialize Window

	window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	gtk_window_set_title(GTK_WINDOW(window), "Invaders Tutorial");
	gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
	gtk_window_set_default_size(GTK_WINDOW(window), 640, 480);
	gtk_window_set_type_hint(GTK_WINDOW(window), GDK_WINDOW_TYPE_HINT_UTILITY);
	g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
	g_signal_connect(window, "key-press-event", G_CALLBACK(on_keydown), NULL);
	g_signal_connect(window, "key-release-event", G_CALLBACK(on_keyup), NULL);

	// Initialize GTK GL Area

	glArea = gtk_gl_area_new();
	gtk_widget_set_vexpand(glArea, TRUE);
	gtk_widget_set_hexpand(glArea, TRUE);
	g_signal_connect(glArea, "realize", G_CALLBACK(on_realize), NULL);
	g_signal_connect(glArea, "render", G_CALLBACK(on_render), NULL);
	gtk_container_add(GTK_CONTAINER(window), glArea);

	// Show widgets

	gtk_widget_show_all(window);
	gtk_main();

	return 0;

}

static void on_realize(GtkGLArea *area) {

	// Debug Message

	g_print("on realize     0\n");

	gtk_gl_area_make_current(area);
	if(gtk_gl_area_get_error(area) != NULL) {
		fprintf(stderr, "Unknown error\n");
		return;
	}

	const GLubyte *renderer = glGetString(GL_RENDER);
	const GLubyte *version = glGetString(GL_VERSION);

	g_print("Renderer: %s\n", renderer);
	g_print("OpenGL version supported %s\n", version);

	glClearColor(1.0f, 1.0f, 1.0f, 1.0f);

	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);

	// Background Sprite

	GLfloat background_vertices[] = {
		0.0, 0.0, 0.0, 0.0, 
		0.0, HEIGHT, 0.0, 1.0,
		WIDTH, HEIGHT, 1.0, 1.0,
		
		0.0, 0.0, 0.0, 0.0,
		WIDTH, HEIGHT, 1.0, 1.0,
		WIDTH, 0.0, 1.0, 0.0
	};
	
	glGenBuffers(1, &background.vbo);
	glBindBuffer(GL_ARRAY_BUFFER, background.vbo);
	glBufferData(
		GL_ARRAY_BUFFER,
		sizeof(background_vertices),
		background_vertices,
		GL_STATIC_DRAW
	);
	
	mat4_identity(background.mvp);
	background.tex = shader_load_texture("sprites/background.png");
	
	// Player Sprite

	GLfloat player_vertices[] = {
		-22.0, -22.0, 0.0, 0.0, 
		-22.0,  22.0, 0.0, 1.0,
		 22.0,  22.0, 1.0, 1.0,
		
		-22.0, -22.0, 0.0, 0.0,
		 22.0,  22.0, 1.0, 1.0,
		 22.0, -22.0, 1.0, 0.0
	};
	
	glGenBuffers(1, &player.vbo);
	glBindBuffer(GL_ARRAY_BUFFER, player.vbo);
	glBufferData(
		GL_ARRAY_BUFFER,
		sizeof(player_vertices),
		player_vertices,
		GL_STATIC_DRAW
	);
	
	player.pos[0] = WIDTH / 2;
	player.pos[1] = 30.0f;
	player.pos[2] = 0.0;
	player.left = FALSE;
	player.right = FALSE;
	
	mat4_translate(player.pos, player.mvp);
	player.tex = shader_load_texture("sprites/player.png");

	player.num_bullets = 5;
	player.bullets = malloc(player.num_bullets * sizeof(vec3));
	player.active = malloc(player.num_bullets * sizeof(gboolean));

	int i;
	for(i = 0; i < player.num_bullets; i++) {
		player.active[i] = FALSE;
	}

	player.active[0] = TRUE;
	player.bullets[0][0] = WIDTH / 2.0f;
	player.bullets[0][1] = HEIGHT / 2.0f;
	player.bullets[0][2] = 0.0f;

	// Bullet Sprite

	GLfloat bullet_vertices[] = {
		-6.0, -12.0, 0.0, 0.0, 
		-6.0,  12.0, 0.0, 1.0,
		 6.0,  12.0, 1.0, 1.0,
		
		-6.0, -12.0, 0.0, 0.0,
		 6.0,  12.0, 1.0, 1.0,
		 6.0, -12.0, 1.0, 0.0
	};
	
	glGenBuffers(1, &bullet.vbo);
	glBindBuffer(GL_ARRAY_BUFFER, bullet.vbo);
	glBufferData(
		GL_ARRAY_BUFFER,
		sizeof(bullet_vertices),
		bullet_vertices,
		GL_STATIC_DRAW
	);
	
	bullet.tex = shader_load_texture("sprites/bullet.png");

	// Compile Shader Program

	GLint compile_ok = GL_FALSE;
	GLint link_ok = GL_FALSE;

	const char *vs = "shader/vertex.glsl";
	const char *fs = "shader/fragment.glsl";
	program = shader_load_program(vs, fs);

	const char *attribute_name = "coord2d";
	attribute_coord2d = glGetAttribLocation(program, attribute_name);
	if(attribute_coord2d == -1) {
		fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
		return;
	}

	attribute_name = "uv_coord";
	attribute_texcoord = glGetAttribLocation(program, attribute_name);
	if(attribute_texcoord == -1) {
		fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
		return;
	}

	const char *uniform_name = "orthograph";
	GLint uniform_ortho = glGetUniformLocation(program, uniform_name);
	if(uniform_ortho == -1) {
		fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
		return;
	}

	uniform_name = "mvp";
	uniform_mvp = glGetUniformLocation(program, uniform_name);
	if(uniform_mvp == -1) {
		fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
		return;
	}

	uniform_name = "mytexture";
	uniform_mytexture = glGetUniformLocation(program, uniform_name);
	if(uniform_mytexture == -1) {
		fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
		return;
	}

	glUseProgram(program);

	mat4 orthograph;
	mat4_orthagonal(WIDTH, HEIGHT, orthograph);
	glUniformMatrix4fv(uniform_ortho, 1, GL_FALSE, orthograph);

	g_timeout_add(20, on_idle, (void*)area);

}

static void on_render(GtkGLArea *area, GdkGLContext *context) {

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glUseProgram(program);
	glBindVertexArray(vao);

	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, background.tex);
	glUniform1i(uniform_mytexture, 0);

	glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, background.mvp);

	glEnableVertexAttribArray(attribute_coord2d);
	glEnableVertexAttribArray(attribute_texcoord);

	glBindBuffer(GL_ARRAY_BUFFER, background.vbo);
	glVertexAttribPointer(
		attribute_coord2d,
		2,
		GL_FLOAT,
		GL_FALSE,
		sizeof(float) * 4,
		0
	);

	glVertexAttribPointer(
		attribute_texcoord,
		2,
		GL_FLOAT,
		GL_FALSE,
		sizeof(float) * 4,
		(void*)(sizeof(float) * 2)
	);
	glDrawArrays(GL_TRIANGLES, 0, 6);

	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, player.tex);
	glUniform1i(uniform_mytexture, 0);

	mat4_translate(player.pos, player.mvp);
	glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, player.mvp);

	glBindBuffer(GL_ARRAY_BUFFER, player.vbo);
	glVertexAttribPointer(
		attribute_coord2d,
		2,
		GL_FLOAT,
		GL_FALSE,
		sizeof(float) * 4,
		0
	);

	glVertexAttribPointer(
		attribute_texcoord,
		2,
		GL_FLOAT,
		GL_FALSE,
		sizeof(float) * 4,
		(void*)(sizeof(float) * 2)
	);
	glDrawArrays(GL_TRIANGLES, 0, 6);

	glActiveTexture(GL_TEXTURE0);
	glBindTexture(GL_TEXTURE_2D, bullet.tex);
	glUniform1i(uniform_mytexture, 0);

	int i;
	for(i = 0; i < player.num_bullets; i++) {
		
		if(!player.active[0]) {
			continue;
		}

		mat4_translate(player.bullets[i], bullet.mvp);
		glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, bullet.mvp);

		glBindBuffer(GL_ARRAY_BUFFER, bullet.vbo);
		glVertexAttribPointer(
			attribute_coord2d,
			2,
			GL_FLOAT,
			GL_FALSE,
			sizeof(float) * 4,
			0
		);

		glVertexAttribPointer(
			attribute_texcoord,
			2,
			GL_FLOAT,
			GL_FALSE,
			sizeof(float) * 4,
			(void*)(sizeof(float) * 2)
		);
		glDrawArrays(GL_TRIANGLES, 0, 6);

	}

	glDisableVertexAttribArray(attribute_coord2d);
	glDisableVertexAttribArray(attribute_texcoord);

}

static gboolean on_idle(gpointer data) {

	if(player.right) {
		player.pos[0] += 6.0f;
	}

	if(player.left) {
		player.pos[0] -= 6.0f;
	}

	if(player.pos[0] < 0) {
		player.pos[0] = 0.0f;
	} else if(player.pos[0] > WIDTH) {
		player.pos[0] = WIDTH;
	}

	gtk_widget_queue_draw(GTK_WIDGET(data));
	return TRUE;

}

static gboolean on_keydown(GtkWidget *widget, GdkEventKey *event) {

	switch(event->keyval) {
		case GDK_KEY_Left:
			player.left = TRUE;
		break;
		case GDK_KEY_Right:
			player.right = TRUE;
		break;
	}

}

static gboolean on_keyup(GtkWidget *widget, GdkEventKey *event) {

	switch(event->keyval) {
		case GDK_KEY_Left:
			player.left = FALSE;
		break;
		case GDK_KEY_Right:
			player.right = FALSE;
		break;
	}

}

Compile with:

$ gcc -c -o DashGL/dashgl.o DashGL/dashgl.c -lepoxy -lpng -lm
$ gcc `pkg-config --cflags gtk+-3.0` main.c DashGL/dashgl.o `pkg-config --libs gtk+-3.0` \
-lepoxy -lm -lpng

Run with:

$ ./a.out