游戏引擎从零开始(28)-windowResize

本章节，我们实现window的resize的效果，更改窗口大小时，设置viewport。

windowResize

事件传递的路径：

Application::OnWindowResize
Renderer::OnWindowResize
RenderCommand::SetViewport
OpenGLRendererAPI::SetViewport

Application增加OnWindowResize，增加m_Minimized字段，当窗口缩小到0时，不做渲染处理。

c++ 复制代码

private:
    bool OnWindowClose(WindowCloseEvent& e);
    bool OnWindowResize(WindowResizeEvent& e);
private:
    Scope<Window> m_Window;
    ImGuiLayer* m_ImGuiLayer;
    bool m_Running = true;
    // 最小化标记，此时不做渲染
    bool m_Minimized = false;
    LayerStack m_LayerStack;
    float m_LastFrameTime = 0;

Sandbox/Hazel/src/Hazel/Application.cpp

c++ 复制代码

void Application::OnEvent(Event &e) {
    EventDispatcher dispatcher(e);
    dispatcher.Dispatch<WindowCloseEvent>(BIND_EVENT_FN(OnWindowClose));
    // 增加windowResize事件分发
    dispatcher.Dispatch<WindowResizeEvent>(BIND_EVENT_FN(OnWindowResize));
    ...
}

bool Application::OnWindowResize(Hazel::WindowResizeEvent &e) {
    if (e.GetWidth() == 0 || e.GetHeight() == 0) {
        m_Minimized = true;
        return false;
    }
    m_Minimized = false;
    uint32_t pixelWidth = e.GetWidth(), pixelHeight = e.GetHeight();
    m_Window->GetPixelSize(pixelWidth, pixelHeight);
    HZ_INFO("width = {0}, height = {1}, pixelWidth = {2}, pixelHeight = {3}", e.GetWidth(), e.GetHeight(), pixelWidth, pixelHeight);
    Renderer::OnWindowResize(pixelWidth, pixelHeight);
    return false;
}

void Application::Run() {
    while (m_Running) {
        float time = glfwGetTime();
        Timestep timestep = time - m_LastFrameTime;
        m_LastFrameTime = time;

        if (!m_Minimized) {
            for (Layer *layer: m_LayerStack) {
                layer->OnUpdate(timestep);
            }
        }
        ...
      }
  }
  ...

注意！！OpenGL的setViewport方法宽高设置的是像素，glfw的size改变回调中传回来的是坐标，mac的retina屏幕像素是坐标的两倍，参考下图中日志。

通过glfwGetFramebufferSize方法将坐标转换成像素值。参考stackoverflow帖子：
Why retina screen coordinate value is twice the value of pixel value

Window中增加获取真实像素值的接口,WindowsWindow中增加实现

Sandbox/Hazel/src/Hazel/Core/Window.h

c++ 复制代码

virtual void GetPixelSize(uint32_t& width, uint32_t& height) const {
    width = GetWidth();
    height = GetHeight();
};

Sandbox/Hazel/src/Hazel/Platform/Windows/WindowsWindow.h

c++ 复制代码

namespace Hazel{
    class WindowsWindow : public Window{
    public:
        void GetPixelSize(uint32_t& width, uint32_t& height) const override;

        WindowsWindow(const WindowProps& props);

        virtual ~WindowsWindow();
    ...
    }
}

Sandbox/Hazel/src/Hazel/Platform/Windows/WindowsWindow.cpp

c++ 复制代码

void WindowsWindow::GetPixelSize(uint32_t& width, uint32_t& height) const {
    glfwGetFramebufferSize(m_Window, reinterpret_cast<int *>(&width), reinterpret_cast<int *>(&height));
}

按顺序，整个调用链条上的类，都需要增加OnWindowResize接口

Sandbox/Hazel/src/Hazel/Renderer/Renderer.h

c++ 复制代码

static void OnWindowResize(uint32_t width, uint32_t height);

Sandbox/Hazel/src/Hazel/Renderer/Renderer.cpp

c++ 复制代码

void Renderer::OnWindowResize(uint32_t width, uint32_t height) {
    RenderCommand::SetViewport(0, 0, width, height);
}

Sandbox/Hazel/src/Hazel/Renderer/RenderCommand.h

c++ 复制代码

inline static void SetViewport(uint32_t x, uint32_t y, uint32_t width, uint32_t height) {
    s_RendererAPI->SetViewport(x, y, width, height);
}

Sandbox/Hazel/src/Hazel/Renderer/RendererAPI.h

c++ 复制代码

virtual void SetViewport(uint32_t x, uint32_t y, uint32_t width, uint32_t height) = 0;

Sandbox/Hazel/src/Hazel/Platform/OpenGL/OpenGLRendererAPI.h

c++ 复制代码

#include "Renderer/RendererAPI.h"
namespace Hazel {
    class OpenGLRendererAPI : public RendererAPI{
    public:
        ...
        void Init() override;
        void SetViewport(uint32_t x, uint32_t y, uint32_t width, uint32_t height) override;
    };
}

Sandbox/Hazel/src/Hazel/Platform/OpenGL/OpenGLRendererAPI.cpp

c++ 复制代码

void OpenGLRendererAPI::SetViewport(uint32_t x, uint32_t y, uint32_t width, uint32_t height) {
    // mac 屏幕上有问题，不知道为啥
    glViewport(x, y, width, height);
}

完整代码参考:
github.com/summer-go/H...

代码维护

最后花一点时间，整理下整个工程的代码，将src/Hazel中的大部分文件挪到src/Hazel/Core下

完整代码参考：
github.com/summer-go/H...