WIP fragment shader demo

8 files changed, 133 insertions, 31 deletions

diff --git a/draw.c b/draw.c
deleted file mode 100644
index 0dfa09c..0000000
--- a/draw.c
+++ /dev/null
@@ -1,6 +0,0 @@
-#include "draw.h"
-
-void draw(GLFWwindow* window) {
-	glClearColor(1.f, 0.f, 1.f, 1.0f);
-	glClear(GL_COLOR_BUFFER_BIT);
-}
diff --git a/draw.h b/draw.h
deleted file mode 100644
index 617569b..0000000
--- a/draw.h
+++ /dev/null
@@ -1,7 +0,0 @@
-#pragma once
-
-#include <GLFW/glfw3.h>
-
-/** @brief draw loop iteration, called once for every frame */
-void draw(GLFWwindow*);
-
diff --git a/hello.frag b/hello.frag
index b88dc43..a804a77 100644
--- a/hello.frag
+++ b/hello.frag
@@ -1,6 +1,13 @@
 #version 330 core
+out vec4 FragColor;
 
 void main() {
-  gl_FragColor = vec4(gl_FragCoord.xy, 0, 1);
+	FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
 }
 
+// #version 330 core
+//
+// void main() {
+//   gl_FragColor = vec4(gl_FragCoord.xy, 0, 1);
+// }
+//
diff --git a/hello.vert b/hello.vert
index e69de29..4af0bdf 100644
--- a/hello.vert
+++ b/hello.vert
@@ -0,0 +1,7 @@
+#version 330 core
+layout (location = 0) in vec3 aPos;
+
+void main() {
+	gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+}
+
diff --git a/main.c b/main.c
index ab5f97b..8ac0ca2 100644
--- a/main.c
+++ b/main.c
@@ -1,40 +1,77 @@
 #include <stdlib.h>
+#include <GL/glew.h>
 #include <GLFW/glfw3.h>
 
-#include "draw.h"
+#include "shader.h"
 #include "die.h"
 
-void resize_handler(GLFWwindow* window, int width, int height) {
-	glViewport(0, 0, width, height);
+#include "hello_vert.h"
+#include "hello_frag.h"
+
+void prepare_tri(GLuint* VBO, GLuint* VAO) {
+	const float vertices[] = {
+		-0.5f, -0.5f, 0.0f,
+		0.5f, -0.5f, 0.0f,
+		0.0f,  0.5f, 0.0f,
+	};
+
+	// initialize vertex {buffer,attribute} object buffers
+	glGenBuffers(1, VBO);
+	glBindBuffer(GL_ARRAY_BUFFER, *VBO);
+	glGenBuffers(1, VAO);
+	glBindVertexArray(*VAO);
+
+	// copy vertex data into VBO
+	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+	// set VAO pointers
+	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+	glEnableVertexAttribArray(0);
 }
 
 int main(int argc, char** argv) {
 	glfwInit();
-
 	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
 	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
-
 	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 
-	int width = 800, height = 600;
-	GLFWwindow* window = glfwCreateWindow(width, height, "vis", NULL, NULL);
+	// force floating window w/ i3
+	glfwWindowHint(GLFW_FLOATING, GL_TRUE);
+	glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
 
-	if (window == NULL) {
-		glfwTerminate();
+	// initialize window
+	GLFWwindow* window = glfwCreateWindow(800, 600, "vis", NULL, NULL);
+	if (window == NULL)
 		die("error: could not create window\n");
-	}
-
 	glfwMakeContextCurrent(window);
-	glfwSetFramebufferSizeCallback(window, resize_handler);
-	resize_handler(window, width, height);
 
+	// initialize GLEW
+	glewInit();
+
+	// create single triangle
+	GLuint VBO, VAO;
+	prepare_tri(&VBO, &VAO);
+
+	// prepare shaders
+	GLuint shader = link_shaders(
+		vert_shader(hello_vert, hello_vert_size),
+		frag_shader(hello_frag, hello_frag_size)
+	);
+
+	// main draw loop
 	while (!glfwWindowShouldClose(window)) {
-		draw(window);
-		glfwSwapBuffers(window);
 		glfwPollEvents();
+
+		glClearColor(1.f, 0.f, 1.f, 1.0f);
+		glClear(GL_COLOR_BUFFER_BIT);
+
+		glUseProgram(shader);
+		glBindVertexArray(VAO);
+		glDrawArrays(GL_TRIANGLES, 0, 3);
+
+		glfwSwapBuffers(window);
 	}
 
-	glfwTerminate();
 	return EXIT_SUCCESS;
 }
 
diff --git a/makefile b/makefile
index 539ac68..42f4e1a 100644
--- a/makefile
+++ b/makefile
@@ -1,5 +1,8 @@
 LDFLAGS += -lglfw
 LDFLAGS += -lOpenGL
+LDFLAGS += -lGLEW
+
+CFLAGS += -g
 
 .PHONY: FORCE
 
@@ -7,7 +10,7 @@ all: main FORCE
 
 main: main.o
 main: die.o
-main: draw.o
+main: shader.o
 main: hello_frag.o
 main: hello_vert.o
 
diff --git a/shader.c b/shader.c
new file mode 100644
index 0000000..df17d5d
--- /dev/null
+++ b/shader.c
@@ -0,0 +1,48 @@
+#include "shader.h"
+
+#include "die.h"
+
+void check_shader(GLuint shader) {
+	int success;
+	char debug[LOG_MAX];
+	glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
+	if (success) return;
+	glGetShaderInfoLog(shader, LOG_MAX, NULL, debug);
+	die("error: shader compilation failed:\n%s\n", debug);
+}
+
+void check_program(GLuint program) {
+	int success;
+	char debug[LOG_MAX];
+	glGetProgramiv(program, GL_LINK_STATUS, &success);
+	if (success) return;
+	glGetProgramInfoLog(program, LOG_MAX, NULL, debug);
+	die("error: shader linking failed:\n%s\n", debug);
+}
+
+GLuint load_shader(GLenum type, const char* const src, size_t src_size) {
+	GLuint shader = glCreateShader(type);
+	glShaderSource(shader, 1, &src, (const int*) &src_size);
+	glCompileShader(shader);
+	check_shader(shader);
+	return shader;
+}
+
+GLuint frag_shader(const char* const src, size_t src_size) {
+	return load_shader(GL_FRAGMENT_SHADER, src, src_size);
+}
+GLuint vert_shader(const char* const src, size_t src_size) {
+	return load_shader(GL_VERTEX_SHADER, src, src_size);
+}
+
+GLuint link_shaders(GLuint vert, GLuint frag) {
+	GLuint shader = glCreateProgram();
+	glAttachShader(shader, vert);
+	glAttachShader(shader, frag);
+	glLinkProgram(shader);
+	check_program(shader);
+	glDeleteShader(vert);
+	glDeleteShader(frag);
+	return shader;
+}
+
diff --git a/shader.h b/shader.h
new file mode 100644
index 0000000..6a4739e
--- /dev/null
+++ b/shader.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <stdlib.h>
+#include <GL/glew.h>
+#include <GL/gl.h>
+#include <GLFW/glfw3.h>
+
+#define LOG_MAX 512
+
+GLuint frag_shader(const char* const src, size_t src_size);
+GLuint vert_shader(const char* const src, size_t src_size);
+GLuint link_shaders(GLuint vert, GLuint frag);
+