add a rectangle shader

src/gui/Shaders/RectShader.cc

@@ -0,0 +1,18 @@
+#include "RectShader.h"
+#include "Runtime.h"
+
+RectShader::RectShader()
+{
+    std::string v_path = Runtime::find(Runtime::SHADER, "rect.v");
+    std::string f_path = Runtime::find(Runtime::SHADER, "rect.f");
+
+    m_program = glcxx::Program::create(
+            glcxx::Shader::create_from_file(GL_VERTEX_SHADER, v_path.c_str()),
+            glcxx::Shader::create_from_file(GL_FRAGMENT_SHADER, f_path.c_str()),
+            "coords", 0);
+
+    m_uniforms.viewport_size = m_program->get_uniform_location("viewport_size");
+    m_uniforms.color = m_program->get_uniform_location("color");
+    m_uniforms.position = m_program->get_uniform_location("position");
+    m_uniforms.size = m_program->get_uniform_location("size");
+}

src/gui/Shaders/RectShader.h

@@ -0,0 +1,46 @@
+#ifndef RECTSHADER_H
+#define RECTSHADER_H
+
+#include "glcxx.hpp"
+#include <memory>
+
+class RectShader
+{
+public:
+    RectShader();
+
+    void use() { m_program->use(); }
+
+    void set_viewport_size(int width, int height)
+    {
+        glUniform2i(m_uniforms.viewport_size, width, height);
+    }
+
+    void set_color(float r, float g, float b, float a)
+    {
+        glUniform4f(m_uniforms.color, r, g, b, a);
+    }
+
+    void set_position(int x, int y)
+    {
+        glUniform2i(m_uniforms.position, x, y);
+    }
+
+    void set_size(int x, int y)
+    {
+        glUniform2i(m_uniforms.size, x, y);
+    }
+
+protected:
+    std::shared_ptr<glcxx::Program> m_program;
+
+    struct
+    {
+        GLint viewport_size;
+        GLint color;
+        GLint position;
+        GLint size;
+    } m_uniforms;
+};
+
+#endif