add handlers to allow imgui code with no access to main loop

include/NazaraImgui/NazaraImgui.hpp

@@ -8,6 +8,7 @@
 #include <NazaraImgui/Config.hpp>
 
 #include <imgui.h>
+#include <unordered_set>
 
 namespace Nz
 {
@@ -19,6 +20,12 @@ namespace Nz
     class Texture;
     class Window;
 
+    struct ImguiHandler
+    {
+    public:
+        virtual void OnRenderImgui() = 0;
+    };
+
     class Imgui : public Nz::ModuleBase<Imgui>
     {
         friend ModuleBase;
@@ -34,6 +41,10 @@ namespace Nz
         void Update(Nz::Window& window, float dt);
         void Render(Nz::RenderWindow& window, Nz::RenderFrame& frame);
 
+        // User-defined
+        void AddHandler(ImguiHandler* handler);
+        void RemoveHandler(ImguiHandler* handler);
+
         // Clipboard functions
         static void SetClipboardText(void* userData, const char* text);
         static const char* GetClipboardText(void* userData);
@@ -79,6 +90,8 @@ namespace Nz
         std::shared_ptr<Nz::RenderBuffer> m_uboBuffer;
         std::shared_ptr<Nz::Texture> m_fontTexture;
 
+        std::unordered_set<ImguiHandler*> m_handlers;
+
         static Imgui* s_instance;
     };
 }

src/NazaraImgui/NazaraImgui.cpp

@@ -312,10 +312,23 @@ namespace Nz
 
     void Imgui::Render(Nz::RenderWindow& window, Nz::RenderFrame& frame)
     {
+        for (auto* handler : m_handlers)
+            handler->OnRenderImgui();
+
         ImGui::Render();
         RenderDrawLists(window, frame, ImGui::GetDrawData());
     }
 
+    void Imgui::AddHandler(ImguiHandler* handler)
+    {
+        m_handlers.insert(handler);
+    }
+
+    void Imgui::RemoveHandler(ImguiHandler* handler)
+    {
+        m_handlers.erase(handler);
+    }
+
     void Imgui::SetClipboardText(void* userData, const char* text)
     {
         Imgui* backend = static_cast<Imgui*>(userData);