Method begin_frame

libraries/lib-app-base/src/gl-imgui.cpp:393–442

    }
    
    void imgui_instance::begin_frame(const uint32_t width, const uint32_t height)
    {
        ImGui::SetCurrentContext(data.context);
        if (!data.FontTexture) create_render_objects();

        ImGuiIO & io = ImGui::GetIO();

        // Setup time step
        double current_time = glfwGetTime();
        io.DeltaTime = data.Time > 0.0 ? (float)(current_time - data.Time) : (float)(1.0f / 60.0f);
        data.Time = current_time;

        for (int i = 0; i < 3; i++)
        {
            // If a mouse press event came, always pass it as "mouse held this frame",
            // so we don't miss click-release events that are shorter than 1 frame
            io.MouseDown[i] = data.MousePressed[i] || glfwGetMouseButton(data.window, i) != 0;
            data.MousePressed[i] = false;
        }

        io.MouseWheel = data.MouseWheel;
        data.MouseWheel = 0.0f;

        // Hide OS mouse cursor if ImGui is drawing it
        glfwSetInputMode(data.window, GLFW_CURSOR, io.MouseDrawCursor ? GLFW_CURSOR_HIDDEN : GLFW_CURSOR_NORMAL);

        // Don't muck with the state if minimized
        if (!glfwGetWindowAttrib(data.window, GLFW_ICONIFIED))
        {
            // Setup display size (every frame to accommodate for window resizing)
            int w = width;
            int h = height;
            int display_w = width;
            int display_h = height;

            // Only use glfw window size if we have not passed in a texture size that
            // we are rendering to 
            if (w == 0 || h == 0)
            {
                glfwGetWindowSize(data.window, &w, &h);
                glfwGetFramebufferSize(data.window, &display_w, &display_h);
            }

            io.DisplaySize = ImVec2((float)w, (float)h);
            io.DisplayFramebufferScale = ImVec2(w > 0 ? ((float)display_w / w) : 0, h > 0 ? ((float)display_h / h) : 0);
        }

        // Start the frame
        ImGui::NewFrame();
    }
    
    void imgui_instance::end_frame()
    {