Unable to render SDL logic under Dear ImGui.

[vict0rfr]

Similar issue to #4264, but I don't have a flickering problem, and I am not getting what I need under Dear ImGui. I can only have either one.

I am implementing this a bit differently. And the first area I would try looking at is the way I'm dereferencing pointers. I have not other way to initialize io after CreateContext() but still make it available to ImguiBackend::drawImgui. I have tried moving the this->_logic.draw() call everywhere in the method and it won't change a thing. Does SDL_GL_SwapWindow only present OpenGL stuff? Hence why I'm not seeing any SDL logic?

void ImguiBackend::drawImgui(Graphics &p_graphics) {
    int display_w, display_h;
    SDL_GetWindowSizeInPixels(this->_window, &display_w, &display_h);
    io->DisplaySize = ImVec2((float)display_w, (float)display_h);
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplSDL3_NewFrame();
    ImGui::NewFrame();

    ImGui::ShowDemoWindow();

    this->_logic.draw(p_graphics);

    // Rendering
    ImGui::Render();
    glViewport(0, 0, (int)io->DisplaySize.x, (int)io->DisplaySize.y);
    glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
    glClear(GL_COLOR_BUFFER_BIT);

    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
    SDL_GL_SwapWindow(this->_window);
}

I have separated my code into multiple classes and I'm calling the draw methods in my main game loop. It works, see picture but obviously my SDL code won't run under it. It's a simple fluid simulation that doesn't create SDL_Textures, it's only drawing lines and adding color (for the moment (: )

void Logic::draw(Graphics &p_graphics) {
    SDL_SetRenderDrawColor(p_graphics.getRenderer(), 255, 255, 255, 255);

    for (int x = 0; x <= globals::SCREEN_SIZE; x += globals::GRID_SIZE) { //vertical lines
        SDL_RenderLine(p_graphics.getRenderer(), x, 0, x, globals::SCREEN_SIZE);
    }

    for (int y = 0; y <= globals::SCREEN_SIZE; y += globals::GRID_SIZE) { //horizontal lines
        SDL_RenderLine(p_graphics.getRenderer(), 0, y, globals::SCREEN_SIZE, y);
    }

    if (this->_mouseX != NULL && this->_mouseY != NULL) {
        SDL_SetRenderDrawBlendMode(p_graphics.getRenderer(), SDL_BLENDMODE_BLEND);
        for (int a = 0; a < globals::N * globals::N; a++) {
            if (this->_densityGrid[a]) {
                SDL_SetRenderDrawColor(p_graphics.getRenderer(), 255, 0, 0, this->_densityGrid[a]);
                int newJ = floor(a / globals::N); // vertical pos
                int newI = a - newJ * globals::N; // horizontal pos

                SDL_FRect rect;
                rect.x = newI * globals::GRID_SIZE + 1;
                rect.y = newJ * globals::GRID_SIZE + 1;
                rect.w = globals::GRID_SIZE - 1;
                rect.h = globals::GRID_SIZE - 1;

                SDL_RenderRect(p_graphics.getRenderer(), &rect);
                SDL_RenderFillRect(p_graphics.getRenderer(), &rect);
            }
        }
    }
}

Result:

[vict0rfr]

Update: Found out the problem was that I was using a GL Context and a SDL_Renderer. Dear ImGui would be in my GL Context and my fluid sim SDL Logic would be in the SDL_Renderer. This means that I can't render two "contexts" at the same time. Instead I opted to switch to the SDL_Renderer backend, so that I could have all my logic/Dear ImGui in one renderer.