build and use imgui from externals, make the imgui demo work

external/CMakeLists.txt

@@ -2,3 +2,18 @@ option(NNG_SETSTACKSIZE "Use rlimit for thread stack size" ON)
 set(NNG_TESTS OFF)
 set(NNG_ENABLE_NNGCAT OFF)
 add_subdirectory(nng)
+
+find_package(SDL2 REQUIRED)
+
+add_library(imgui SHARED
+    imgui/imgui.cpp
+    imgui/imgui_demo.cpp
+    imgui/imgui_draw.cpp
+    imgui/imgui_tables.cpp
+    imgui/imgui_widgets.cpp
+    imgui/backends/imgui_impl_sdl.cpp
+    imgui/backends/imgui_impl_sdlrenderer.cpp
+)
+
+target_include_directories(imgui PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/imgui)
+target_link_libraries(imgui PUBLIC SDL2::SDL2)

external/imgui/imconfig.h

@@ -27,8 +27,8 @@
 //#define IMGUI_API __declspec( dllimport )
 
 //---- Don't define obsolete functions/enums/behaviors. Consider enabling from time to time after updating to avoid using soon-to-be obsolete function/names.
-//#define IMGUI_DISABLE_OBSOLETE_FUNCTIONS
+#define IMGUI_DISABLE_OBSOLETE_FUNCTIONS
-//#define IMGUI_DISABLE_OBSOLETE_KEYIO                      // 1.87: disable legacy io.KeyMap[]+io.KeysDown[] in favor io.AddKeyEvent(). This will be folded into IMGUI_DISABLE_OBSOLETE_FUNCTIONS in a few versions.
+#define IMGUI_DISABLE_OBSOLETE_KEYIO                      // 1.87: disable legacy io.KeyMap[]+io.KeysDown[] in favor io.AddKeyEvent(). This will be folded into IMGUI_DISABLE_OBSOLETE_FUNCTIONS in a few versions.
 
 //---- Disable all of Dear ImGui or don't implement standard windows/tools.
 // It is very strongly recommended to NOT disable the demo windows and debug tool during development. They are extremely useful in day to day work. Please read comments in imgui_demo.cpp.

src/CMakeLists.txt

@@ -20,12 +20,9 @@ find_package(SDL2 REQUIRED)
 
 add_executable(doompanning doompanning.cc)
 target_compile_features(doompanning PRIVATE cxx_std_17)
-#target_compile_options(doompanning PRIVATE ${IMGUI_CFLAGS})
-#target_include_directories(doompanning PRIVATE ${IMGUI_INCLUDE_DIRS})
 target_link_libraries(doompanning
     PRIVATE dp_common
-    #PRIVATE ${IMGUI_LIBRARIES}
+    PRIVATE imgui
-    PRIVATE SDL2::SDL2-static
     )
 
 add_executable(doomsim doomsim.cc)

src/doompanning.cc

@@ -1,8 +1,9 @@
 #include <cstdlib>
 #include <nng/nng.h>
 
-//#include <imgui.h>
+#include <imgui.h>
-//#include <backends/imgui_impl_sdl.h>
+#include <backends/imgui_impl_sdl.h>
+#include <backends/imgui_impl_sdlrenderer.h>
 #include <SDL.h>
 
 #include "dp_common.h"
@@ -10,7 +11,7 @@
 
 void dp_sdl_fatal(const char *const msg)
 {
-    log_fatal("%s: %s", SDL_GetError());
+    log_fatal("%s: %s", msg, SDL_GetError());
     abort();
 }
 
@@ -18,6 +19,10 @@ static const size_t NumDooms = 3;
 
 int doom_controller_loop(nng_socket pubSock, nng_socket subSock, SDL_Window *window, SDL_Renderer *renderer)
 {
+    bool show_demo_window = true;
+    bool show_another_window = false;
+    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
+
     bool done = false;
 
     while (!done)
@@ -25,11 +30,28 @@ int doom_controller_loop(nng_socket pubSock, nng_socket subSock, SDL_Window *win
         SDL_Event event;
         while (SDL_PollEvent(&event))
         {
+            ImGui_ImplSDL2_ProcessEvent(&event);
+
             if (event.type == SDL_QUIT)
                 done = true;
             if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
                 done = true;
         }
+
+        // Start the Dear ImGui frame
+        ImGui_ImplSDLRenderer_NewFrame();
+        ImGui_ImplSDL2_NewFrame();
+        ImGui::NewFrame();
+
+        if (show_demo_window)
+            ImGui::ShowDemoWindow(&show_demo_window);
+
+        // Rendering
+        ImGui::Render();
+        SDL_SetRenderDrawColor(renderer, (Uint8)(clear_color.x * 255), (Uint8)(clear_color.y * 255), (Uint8)(clear_color.z * 255), (Uint8)(clear_color.w * 255));
+        SDL_RenderClear(renderer);
+        ImGui_ImplSDLRenderer_RenderDrawData(ImGui::GetDrawData());
+        SDL_RenderPresent(renderer);
     }
 
     return 0;
@@ -64,10 +86,11 @@ int main(int argc, char *argv[])
     if (!renderer)
         dp_sdl_fatal("SDL_CreateRenderer");
 
-    //IMGUI_CHECKVERSION();
+    IMGUI_CHECKVERSION();
-    //ImGui::CreateContext();
+    ImGui::CreateContext();
-    //ImGui::StyleColorsDark();
+    ImGui::StyleColorsDark();
-    //ImGui_ImplSDL2_InitForSDLRenderer(window);
+    ImGui_ImplSDL2_InitForSDLRenderer(window, renderer);
+    ImGui_ImplSDLRenderer_Init(renderer);
 
     int ret = doom_controller_loop(pubSock, subSock, window, renderer);