xo-imgui: ex4 refactor [wip]

xo-imgui/example/ex4/imgui_ex4.cpp

@@ -1,11 +1,46 @@
 /* imgui_ex4.cpp */
 
 #include "xo/imgui/VulkanApp.hpp"
+#include <backends/imgui_impl_sdl2.h>
+#include <backends/imgui_impl_vulkan.h>
 #include <iostream>
 
+namespace {
+    ImDrawData *
+    imgui_draw_frame(ImGuiContext * imgui_cx)
+    {
+        // Start the Dear ImGui frame
+        ImGui_ImplVulkan_NewFrame();
+        ImGui_ImplSDL2_NewFrame();
+        ImGui::NewFrame();
+
+        // Create a simple ImGui window
+        ImGui::Begin("Hello, Vulkan + SDL2!");
+        ImGui::Text("This is a minimal ImGui + Vulkan + SDL2 example!");
+        static float f = 0.0f;
+        static int counter = 0;
+        ImGui::SliderFloat("float", &f, 0.0f, 1.0f);
+        if (ImGui::Button("Button"))
+            ++counter;
+        ImGui::SameLine();
+        ImGui::Text("counter = %d", counter);
+        ImGui::Text("Application average %.3f ms/frame (%.1f FPS)",
+                    1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
+        ImGui::End();
+
+        // Rendering
+        ImGui::Render();
+        ImDrawData* draw_data = ImGui::GetDrawData();
+
+        return draw_data;
+    }
+}
+
 int main() {
     VulkanApp app;
 
+    app.assign_imgui_draw_frame(imgui_draw_frame);
+
     try {
         app.run();
     } catch (const std::exception& e) {

xo-imgui/include/xo/imgui/VulkanApp.hpp

@@ -16,6 +16,9 @@ public:
 public:
     VulkanApp() = default;
 
+    /** set imgui draw function **/
+    void assign_imgui_draw_frame(ImguiDrawFn fn);
+
     void run();
 
 private:
@@ -72,6 +75,9 @@ private:
     uint32_t current_frame_ = 0;
     uint32_t graphics_queue_family_ = 0;
     bool quit_ = false;
+
+    /** draw imgui **/
+    ImguiDrawFn imgui_draw_frame_;
 };
 
 /* end VulkanApp.hpp */

xo-imgui/src/imgui/VulkanApp.cpp

@@ -8,6 +8,12 @@
 
 constexpr std::size_t c_max_frames_in_flight = 2;
 
+void
+VulkanApp::assign_imgui_draw_frame(ImguiDrawFn fn)
+{
+    this->imgui_draw_frame_ = std::move(fn);
+}
+
 void
 VulkanApp::run() {
     this->init_window();