Win32 程序以恒定速度卡住

Question

我正在使用 win32 API，并且编写了一个简单的程序，每秒绘制 100 个随机像素十次。但是，当我编译并运行代码时，屏幕大约每秒刷新一次。我会对其进行调试，但我正在锁定的设备上工作，并且我的 IDE 没有调试功能。我已经更改了我能找到的所有引用计时器函数的变量，但没有任何效果。我正在使用 gcc 进行编译。这是代码：

#include <windows.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>

using namespace std;

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
const int ID_TIMER = 1;

void DrawRandom(HDC hdc);


//Double buffering implementation 
static void Paint(HDC hdc, RECT* prc){
    //Declares our varibles
    HDC hdcMem;
    HBITMAP hbmMem, hbmOld;
    HBRUSH hbrBkGnd;
    POINT Border;
    //Creates creates compatible device context
    hdcMem = CreateCompatibleDC(hdc);

    //Create bitmap big enough for our display
    hbmMem = CreateCompatibleBitmap(hdc, prc->right, prc->bottom);

    //Select the bitmap into the offscreen DC
    hbmOld = (HBITMAP)SelectObject(hdcMem, hbmMem);

    //Erase the background
    hbrBkGnd = CreateSolidBrush(GetSysColor(COLOR_WINDOW));
    FillRect(hdcMem, prc, hbrBkGnd);
    DeleteObject(hbrBkGnd);

    //Gets the size of our border
    Border.x = prc->right;
    Border.y = prc->bottom;

    
    //Draws random pixels
    DrawRandom(hdcMem);

    //BLT the changes to the screen dc
    BitBlt(hdc, 0, 0, prc->right, prc->bottom, hdcMem, 0, 0, SRCCOPY);

    //Memory manegment
    SelectObject(hdcMem, hbmOld);
    DeleteObject(hbmMem);
    DeleteDC(hdcMem);
}
//Sets up our window
int WINAPI 
WinMain (HINSTANCE hInstance, HINSTANCE hPrevInst, LPTSTR lpCmdLine, int nShowCmd) {
    
    MSG  msg;
    WNDCLASSW wc = {0};

    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpszClassName = L"Cube!";
    wc.hInstance     = hInstance;
    wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
    wc.lpfnWndProc   = WndProc;
    wc.hCursor       = LoadCursor(0, IDC_ARROW);

    

    RegisterClassW(&wc);
    CreateWindowW(wc.lpszClassName, L"Cube",
                WS_OVERLAPPEDWINDOW | WS_VISIBLE,
                100, 100, 300, 250, NULL, NULL, hInstance, NULL);

    while (GetMessage(&msg, NULL, 0, 0)) {
    
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }


    return (int) msg.wParam;
}
//Calls our buffer and initilizes timer
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg,
    WPARAM wParam, LPARAM lParam) {
    
    switch(msg) {
         //Initilizes timer
        case WM_CREATE:
        {
            UINT ret;

            ret = SetTimer(hwnd, ID_TIMER, 50, NULL);
        }
        break;
        case WM_ERASEBKGND:
            //Disables auto clear
            return (LRESULT)1; 
        break;
        //Makes sure the window closes
        case WM_CLOSE:
            DestroyWindow(hwnd);
        break;
        //This is what initilizes the contents of the window
        case WM_PAINT:
        {
            RECT rcClient;
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hwnd, &ps);
            
            GetClientRect(hwnd, &rcClient);
            Paint(hdc, &rcClient);

            EndPaint(hwnd, &ps);
        }
        break;
        //This is where the main update loop is
        case WM_TIMER:
        {
            RECT rcClient;
            HDC hdc = GetDC(hwnd);

            GetClientRect(hwnd, &rcClient);

            Paint(hdc, &rcClient);
        }
        break;
        //Kills the timer
        case WM_DESTROY:
            KillTimer(hwnd, ID_TIMER);
            PostQuitMessage(0);
        break;
        //Make sures the program closes
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

void DrawRandom(HDC hdc){
    srand(time(NULL));
    for(int i = 0;i < 100;i++){
        int x = rand() % 400;
        int y = rand() % 400;

        SetPixel(hdc, x, y, RGB(0,0,0));
    }
}

Answer 1

srand(time(NULL))为伪随机数生成器播种 播种rand() 意味着设置初始值。

由于您在函数内部调用，srand(time(NULL)) 这意味着任何时候调用的DrawRandom()后续调用都rand()将具有相同的值并返回相同的值。 为您提供秒分辨率，这就是为什么您看到更改每秒只发生一次。DrawRandom()time(NULL)time(NULL)