2 files changed, 140 insertions, 0 deletions
diff --git a/include/render.h b/include/render.h
new file mode 100644
index 0000000..7b8a555
--- /dev/null
+++ b/include/render.h
@@ -0,0 +1,11 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include <SDL2/SDL_video.h>
+
+void render_begin(int w, int h);
+void render_end(SDL_Window* win);
+bool render_init(void);
+void render_rect(float x, float y, float w, float h, float r, float g, float b, float a);
+void render_shutdown(void);
diff --git a/src/render.c b/src/render.c
new file mode 100644
index 0000000..8220edb
--- /dev/null
+++ b/src/render.c
@@ -0,0 +1,129 @@
+#include <stdbool.h>
+#include <stdio.h>
+
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_opengles2.h>
+
+#include "quark.h"
+#include "render.h"
+
+/* shader handles */
+static GLuint prog = 0;
+static GLint u_res;
+static GLint u_color;
+static GLuint vbo = 0;
+
+/* helpers */
+static GLuint compile(GLenum type, const char* src);
+
+static GLuint compile(GLenum type, const char* src)
+{
+	GLuint s = glCreateShader(type);
+	glShaderSource(s, 1, &src, NULL);
+	glCompileShader(s);
+
+	GLint ok;
+	glGetShaderiv(s, GL_COMPILE_STATUS, &ok);
+	if (!ok) {
+		char log[512];
+		glGetShaderInfoLog(s, sizeof(log), NULL, log);
+		LOG_ERROR("renderer: shader error: %s", log);
+		glDeleteShader(s);
+		return 0;
+	}
+
+	return s;
+}
+
+void render_begin(int w, int h)
+{
+	glViewport(0, 0, w, h);
+	glClearColor(0.0, 0.0, 0.0, 1.0);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	glUseProgram(prog);
+	glUniform2f(u_res, w, h);
+}
+
+void render_end(SDL_Window* win)
+{
+	SDL_GL_SwapWindow(win);
+}
+
+bool render_init(void)
+{
+	const char* vs =
+		"attribute vec2 a_pos;"
+		"uniform vec2 u_res;"
+		"void main() {"
+		"vec2 p = a_pos / u_res;"
+		"p.y = 1.0 - p.y;"
+		"p = p * 2.0 - 1.0;"
+		"  gl_Position = vec4(p, 0.0, 1.0);"
+		"}";
+
+	const char* fs =
+		"precision mediump float;"
+		"uniform vec4 u_color;"
+		"void main()"
+		"{"
+		"  gl_FragColor = u_color;"
+		"}";
+
+	GLuint v = compile(GL_VERTEX_SHADER, vs);
+	GLuint f = compile(GL_FRAGMENT_SHADER, fs);
+	if (!v || !f)
+		return false;
+
+	prog = glCreateProgram();
+	glAttachShader(prog, v);
+	glAttachShader(prog, f);
+	glBindAttribLocation(prog, 0, "a_pos");
+	glLinkProgram(prog);
+
+	glDeleteShader(v);
+	glDeleteShader(f);
+
+	GLint ok;
+	glGetProgramiv(prog, GL_LINK_STATUS, &ok);
+	if (!ok) {
+		LOG_ERROR("renderer: program link failed");
+		return false;
+	}
+
+	u_res = glGetUniformLocation(prog, "u_res");
+	u_color = glGetUniformLocation(prog, "u_color");
+
+	glGenBuffers(1, &vbo);
+
+	return true;
+}
+
+void render_rect(float x, float y, float w, float h, float r, float g, float b, float a)
+{
+	float verts[12] = {
+		x,    y,
+		x+w,  y,
+		x+w,  y+h,
+
+		x,    y,
+		x+w,  y+h,
+		x,    y+h
+	};
+
+	glBindBuffer(GL_ARRAY_BUFFER, vbo);
+	glBufferData(GL_ARRAY_BUFFER, sizeof(verts), verts, GL_STREAM_DRAW);
+
+	glEnableVertexAttribArray(0);
+	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
+
+	glUniform4f(u_color, r, g, b, a);
+
+	glDrawArrays(GL_TRIANGLES, 0, 6);
+}
+
+void render_shutdown(void)
+{
+	glDeleteProgram(prog);
+	glDeleteBuffers(1, &vbo);
+}