Why is my simple C Windows.h window so laggy?-CodePudding

I'm in the process of exploring options for creating windows applications in C , and today I tried "Windows.h". It was working pretty well (apart from the copious boilerplate code) until I tried rendering text to the window. Compiling times jumped up to like 20 seconds, and the window was extremely laggy. Does anyone know why it is that such a basic program would be so slow?

Window.cpp:

#include "Window.h"
#include <vector>
#include <iostream>

LPCWSTR title = L"hello";
HWND textfield;

LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_CLOSE:
        DestroyWindow(hWnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
        break;
    }
    
    textfield = CreateWindowW(L"STATIC", L"Text is here", 
        WS_VISIBLE | WS_CHILD | WS_BORDER, 20, 20, 300, 25, hWnd, NULL, NULL, NULL);

    return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

Window::Window()
    : m_hInstance(GetModuleHandle(nullptr))
{
    const wchar_t* CLASS_NAME = L"Kai Window Class";

    WNDCLASS wndClass = {};
    wndClass.lpszClassName = CLASS_NAME;
    wndClass.hInstance = m_hInstance;
    wndClass.hIcon = LoadIcon(NULL, IDI_WINLOGO);
    wndClass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndClass.lpfnWndProc = WindowProc;

    RegisterClass(&wndClass);

    DWORD style = WS_CAPTION | WS_MINIMIZEBOX | WS_SYSMENU;

    std::vector<int> AspectRatio = {1920, 1080};

    RECT rect;
    rect.left = AspectRatio.at(0)/2;
    rect.top = AspectRatio.at(1)/2;
    rect.right = AspectRatio.at(0);
    rect.bottom = AspectRatio.at(1);

    AdjustWindowRect(&rect, style, false);

    m_hWnd = CreateWindowEx(
        0,
        CLASS_NAME,
        title,
        style,
        rect.left,
        rect.top,
        rect.right - rect.left,
        rect.bottom - rect.top,
        NULL,
        NULL,
        m_hInstance,
        NULL
    );

    ShowWindow(m_hWnd, SW_SHOW);
}

Window::~Window()
{
    const wchar_t* CLASS_NAME = L"Kai Window Class";

    UnregisterClass(CLASS_NAME, m_hInstance);
}

bool Window::ProcessMessages()
{
    MSG msg = {};

    while (PeekMessage(&msg, nullptr, 0u, 0u, PM_REMOVE))
    {
        if (msg.message == WM_QUIT)
        {
            return false;
        }

        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return true;
}

Window.h:

#pragma once

#include <Windows.h>
#include <Vector>

LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);

class Window
{
public:
    Window();
    Window(const Window&) = delete;
    Window& operator = (const Window&) = delete;
    ~Window();

    bool ProcessMessages();

private:
    HINSTANCE m_hInstance;
    HWND m_hWnd;
};

Main.cpp:

#include <iostream>
#include "Window.h"

int main()
{
    std::cout << "Creating Window...\n";

    Window* pWindow = new Window();


    bool running = true;
    while (running)
    {
        if (!pWindow->ProcessMessages())
        {
            std::cout << "Closing Window...\n";
            running = false;
        }

        // Render

        Sleep(10);
    }

    delete pWindow;

    return 0;
}

CodePudding user response：

It's slow because you are creating a window every time your window fields a message

LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_CLOSE:
        DestroyWindow(hWnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
        break;
    }
    
    ///////////// This should not be here .....
    textfield = CreateWindowW(L"STATIC", L"Text is here", 
        WS_VISIBLE | WS_CHILD | WS_BORDER, 20, 20, 300, 25, hWnd, NULL, NULL, NULL);
    /////////////

    return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

You want to create the label once, not every time the window procedure is called. A good place is in the WM_CREATE handler i.e.

LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_CREATE:
        textfield = CreateWindowW(L"STATIC", L"Text is here", WS_VISIBLE | WS_CHILD | WS_BORDER, 20, 20, 300, 25, hWnd, NULL, NULL, NULL);
        return 0;
    case WM_CLOSE:
        DestroyWindow(hWnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
        break;
    }

    return DefWindowProc(hWnd, uMsg, wParam, lParam);
}