make the imgui window not be focused by default and put math_graphics into a namespace

src/main.cpp

@@ -2,6 +2,7 @@
 #include <stdint.h>
 #include <SDL3/SDL.h>
 #include <imgui.h>
+#include <imgui_internal.h>
 #include <imgui_impl_sdl3.h>
 #include <imgui_impl_sdlgpu3.h>
 
@@ -14,6 +15,8 @@
 #include "../assets/shader/basic_vertex_shader.h"
 #include "../assets/shader/basic_pixel_shader.h"
 
+using namespace M;
+
 SDL_GPUDevice *device;
 SDL_Window    *window;
 
@@ -750,6 +753,7 @@ int main(int argc, char **argv) {
     ImGui_ImplSDLGPU3_Init(&imgui_init_info);
 
     bool show_demo_window = true;
+    bool first_frame      = true;
 
     // MSG Message;
     while (Running) {
@@ -760,6 +764,11 @@ int main(int argc, char **argv) {
         if (show_demo_window)
             ImGui::ShowDemoWindow(&show_demo_window);
 
+        if (first_frame) {
+            ImGui::SetWindowFocus(NULL);
+            first_frame = false;
+        }
+
         SDL_GPUCommandBuffer *command_buffer = SDL_AcquireGPUCommandBuffer(device);
         if (!command_buffer) {
             log_error("Failed to acquire gpu command buffer (%s). Exiting.", SDL_GetError());