Migrate to NanoGUI / Eigen for GUI and linear algebra.

Also introduce a GUI play/pause button.

vis/include/cgl/program.hpp

@@ -0,0 +1,65 @@
+#pragma once
+
+#include <string>
+#include <utility>
+
+#include <nanogui/opengl.h>
+
+#include <cgl/error.hpp>
+#include <cgl/shader.hpp>
+
+#include <util.hpp>
+
+namespace cgl {
+    class Program {
+    protected:
+        GLuint id{};
+
+    public:
+        Program() {
+            id = glCreateProgram();
+        }
+
+        Program(Program &) = delete;
+
+        Program(Program &&o) noexcept {
+            id = std::exchange(o.id, 0);
+        };
+
+        ~Program() {
+            glDeleteProgram(id);
+        }
+
+        operator GLuint() const {
+            return id;
+        }
+
+        [[nodiscard]] int get(GLenum pname) const {
+            GLint res;
+            glGetProgramiv(id, pname, &res);
+            return (int) res;
+        }
+
+        [[nodiscard]] std::string get_info_log() const {
+            auto len = (size_t) get(GL_INFO_LOG_LENGTH);
+            char buffer[len];
+            glGetProgramInfoLog(id, len, nullptr, buffer);
+            return std::string(buffer);
+        }
+
+        template<GLenum mode>
+        void attach(const Shader<mode> &sh) {
+            glAttachShader(id, sh);
+        }
+
+        template<GLenum mode>
+        void detach(const Shader<mode> &sh) {
+            glDetachShader(id, sh);
+        }
+
+        bool link() {
+            glLinkProgram(id);
+            return (bool) get(GL_LINK_STATUS);
+        }
+    };
+}