How can I draw a grid using ImDrawList and AddRectFilled in ImGui?

Question

I'm trying to draw a grid of the dimensions of m_GCodeBuilder.GetBilletSize().x by m_GCodeBuilder.GetBilletSize().y in a new ImGui window right underneath the main menu. My Program class has a Run function with the meat of the program. Here it is:

void Program::Run() {
    SDL_Event e;

    while (m_Running) {
        while (SDL_PollEvent(&e)) {
            m_Renderer.ProcessEvent(&e);

            switch (e.type) {
                case SDL_QUIT: {
                    m_Running = false;
                    break;
                }

                case SDL_WINDOWEVENT: {
                    if (e.window.event == SDL_WINDOWEVENT_RESIZED) {
                        m_Window.UpdateWindowSize();
                    }
                }
            }
        }

        m_Renderer.NewFrame();

        // 
        // Main Menu Bar
        // 
        if (ImGui::BeginMainMenuBar()) {
            // MENU BAR STUFF
            ImGui::EndMainMenuBar();
        }

        float menuHeight = ImGui::GetFrameHeight(); // this is 19

        ImVec2 windowSize = ImGui::GetIO().DisplaySize;
        // Subtract the height of the menu bar
        windowSize.y -= menuHeight;

        // Set the position and size of the window
        ImGui::SetNextWindowPos(ImVec2(0, menuHeight));
        ImGui::SetNextWindowSize(windowSize);

        if (ImGui::Begin("Content", nullptr, ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoBringToFrontOnFocus))
        {   
            // With the billet being 150 x 100 the squareSize ends up being 4 (without resizing the 600 x 600 window)
            const auto squareSize = std::min(windowSize.x / m_GCodeBuilder.GetBilletSize().x, windowSize.y / m_GCodeBuilder.GetBilletSize().y);
            auto drawList = ImGui::GetWindowDrawList();
            ImVec2 windowPos = ImGui::GetWindowPos(); // gets the current position of the cursor in window coordinates

            for (std::int32_t i = 0; i < m_GCodeBuilder.GetBilletSize().x; i++) {
                for (std::int32_t j = 0; j < m_GCodeBuilder.GetBilletSize().y; j++) {
                    const ImVec2 markerMin = ImVec2(windowPos.x + i * squareSize, windowPos.y + j * squareSize);
                    const ImVec2 markerMax = ImVec2(windowPos.x + (i + 1) * squareSize, windowPos.y + (j + 1) * squareSize);

                    spdlog::info("Window position: ({}, {})", windowPos.x, windowPos.y);
                    spdlog::info("Marker min: ({}, {})", markerMin.x, markerMin.y);
                    spdlog::info("Marker max: ({}, {})", markerMax.x, markerMax.y);

                    if ((i + j) % 2 == 0) {
                        drawList->AddRectFilled(markerMin, markerMax, ImGui::GetColorU32(m_GridColor1));
                    } else {
                        drawList->AddRectFilled(markerMin, markerMax, ImGui::GetColorU32(m_GridColor2));
                    }
                }
            }

            ImGui::End();
        }

        m_Renderer.Render();
    }
}

What am I doing wrong? Did I mess up the coordinates? I would really appreciate any help, Mike

How can I draw a grid using ImDrawList and AddRectFilled in ImGui?

0 Answers0