Try out fmt which is a very nice printing/formatting library.

sfmldemo/main.cpp

@@ -1,5 +1,6 @@
 #include "imgui.h"
 #include "imgui-SFML.h"
+#include <fmt/core.h>
 
 #include <SFML/Graphics/CircleShape.hpp>
 #include <SFML/Graphics/RenderWindow.hpp>
@@ -7,10 +8,19 @@
 #include <SFML/Window/Event.hpp>
 
 int main() {
+
+  fmt::print("Setting up a window for you...\n");
+
   sf::RenderWindow window(sf::VideoMode(1920, 1080), "ImGui + SFML = <3");
   // window.setFramerateLimit(60);
   window.setVerticalSyncEnabled(true);
-  ImGui::SFML::Init(window);
+  int res = ImGui::SFML::Init(window);
+  if(res == 1) {
+    fmt::print("ImGui returned result {}\n", res);
+  } else {
+    fmt::print("ImGui returned an error code={}\n", res);
+    return -1;
+  }
 
   sf::CircleShape shape(100.f);
   shape.setFillColor(sf::Color::Green);
@@ -22,6 +32,7 @@ int main() {
       ImGui::SFML::ProcessEvent(window, event);
 
       if (event.type == sf::Event::Closed) {
+        fmt::print("Exiting...\n");
         window.close();
       }
     }

sfmldemo/meson.build

@@ -5,7 +5,8 @@ project('sfmldemo', 'cpp',
 
 sfml_dep = dependency('sfml')
 imgui_dep = dependency('imgui-sfml')
+fmt_dep = dependency('fmt')
 
 executable('sfmldemo', 'main.cpp',
   win_subsystem: 'windows',
-  dependencies: [sfml_dep, imgui_dep])
+  dependencies: [sfml_dep, imgui_dep, fmt_dep])