separating out the file for header

src/main.cpp

@@ -2,22 +2,15 @@
 #include <gtkmm.h>
 #include <iostream>
 
-class MyWindow : public Gtk::Window {
+#include "main.h"
-public:
-  MyWindow();
-  virtual ~MyWindow();
-
-public:
-  Gtk::Button button;
-  void startCapture();
-};
 
 MyWindow::MyWindow() {
   set_title("Basic application");
 
   Gtk::Button button("start capture");
 
-  button.signal_clicked().connect(sigc::mem_fun(*this, &MyWindow::startCapture));
+  button.signal_clicked().connect(
+      sigc::mem_fun(*this, &MyWindow::startCapture));
 
   set_default_size(800, 450);
 
@@ -26,12 +19,7 @@ MyWindow::MyWindow() {
 
 MyWindow::~MyWindow() {}
 
-void MyWindow::startCapture() {
+void MyWindow::startCapture() { std::cout << "start capture" << std::endl; }
-  std::cout << "start capture" << std::endl;
-
-
-}
-
 
 int main(int argc, char **argv) {
   auto app = Gtk::Application::create("org.gtkmm.examples.base");

src/main.h

@@ -0,0 +1,11 @@
+#include <gtkmm.h>
+
+class MyWindow : public Gtk::Window {
+public:
+  MyWindow();
+  virtual ~MyWindow();
+
+public:
+  Gtk::Button button;
+  void startCapture();
+};