From 213e7046d1ceca7591dc6d66e68a227421a508c5 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Mon, 1 Feb 2016 10:19:13 +0100
Subject: Initial commit

---
 .gitignore |   1 +
 Makefile   |   2 +
 glslview.c | 149 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 152 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 glslview.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3acbfea
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+glslview
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..aa6d2b1
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+glslview : glslview.c
+	gcc -o glslview glslview.c -lSDL2 -lGL -lGLEW -Wall
diff --git a/glslview.c b/glslview.c
new file mode 100644
index 0000000..843319f
--- /dev/null
+++ b/glslview.c
@@ -0,0 +1,149 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <GL/glew.h>
+
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_opengl.h>
+
+
+
+static GLint time;
+static GLint res;
+
+
+char * readfile(const char *filename) {
+        FILE *f = fopen(filename, "r");
+        if (!f)
+                return NULL;
+
+        size_t size = 1024;
+        char *buffer = malloc(size+1);
+        size_t count = 0, r;
+
+        do {
+                if (count == size) {
+                        size *= 2;
+                        buffer = realloc(buffer, size+1);
+                }
+
+                r = fread(buffer+count, 1, size-count, f);
+                count += r;
+        } while (r);
+
+        fclose(f);
+
+        buffer[count] = 0;
+
+        return buffer;
+}
+
+void printShaderInfoLog(GLuint obj) {
+        GLint length = 0;
+
+        glGetShaderiv(obj, GL_INFO_LOG_LENGTH, &length);
+
+        if(length > 0) {
+                char log[length];
+
+                glGetShaderInfoLog(obj, sizeof(log), NULL, log);
+                fprintf(stderr, "%s\n", log);
+        }
+}
+
+void printProgramInfoLog(GLuint obj) {
+        GLint length = 0;
+
+        glGetProgramiv(obj, GL_INFO_LOG_LENGTH, &length);
+
+        if(length > 0) {
+                char log[length];
+
+                glGetProgramInfoLog(obj, sizeof(log), NULL, log);
+                fprintf(stderr, "%s\n", log);
+        }
+}
+
+void init(char *filename) {
+        glewInit();
+
+	glDisable(GL_DEPTH_TEST);
+
+        char *shader = readfile(filename);
+        if (!shader) {
+                fprintf(stderr, "Error: unable to read '%s'\n", filename);
+                exit(1);
+        }
+
+        GLuint frag = glCreateShader(GL_FRAGMENT_SHADER);
+        glShaderSource(frag, 1, (const GLchar **)&shader, NULL);
+        glCompileShader(frag);
+        printShaderInfoLog(frag);
+
+        GLuint program = glCreateProgram();
+        glAttachShader(program, frag);
+
+        glLinkProgram(program);
+        printProgramInfoLog(program);
+
+        glBindFragDataLocation(program, 0, "fragColor");
+        time = glGetUniformLocation(program, "time");
+        res = glGetUniformLocation(program, "res");
+
+        glUseProgram(program);
+
+
+}
+
+void render(SDL_Window *window) {
+        int width, height;
+        SDL_GetWindowSize(window, &width, &height);
+
+	glViewport(0, 0, (GLsizei)width, (GLsizei)height);
+
+        glUniform1f(time, SDL_GetTicks());
+        glUniform2f(res, width, height);
+
+	glBegin(GL_QUADS);
+	glVertex2f(-1, -1);
+	glVertex2f(1, -1);
+	glVertex2f(1, 1);
+	glVertex2f(-1, 1);
+	glEnd();
+
+	SDL_GL_SwapWindow(window);
+}
+
+
+int main(int argc, char *argv[]) {
+	bool running = true;
+
+        if (argc != 2) {
+                fprintf(stderr, "Usage: glslview <shader>\n");
+                exit(1);
+        }
+
+	SDL_Init(SDL_INIT_VIDEO);
+
+	SDL_Window *window = SDL_CreateWindow("glslview", 0, 0, 800, 800, SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
+        SDL_GL_CreateContext(window);
+
+        init(argv[1]);
+
+	while (running) {
+		SDL_Event e;
+
+		while( SDL_PollEvent(&e)) {
+			if(e.type == SDL_QUIT) {
+				running = false;
+                                break;
+			}
+		}
+
+		render(window);
+                //usleep(1);
+	}
+
+	return 0;
+}
-- 
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