来自mouse_event的消息

Question

#include <windows.h>
#include <time.h>
#define _USE_MATH_DEFINES 
#include <math.h>

LRESULT CALLBACK WndProc(HWND hwnd,UINT iMsg,WPARAM wParam,LPARAM lParam);
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,PSTR szCmdLine,int iCmdShow)
{
    static wchar_t szAppName[]=L"circle";
    HWND hwnd;
    MSG msg;
    WNDCLASSEX wndclass;

    wndclass.cbSize=sizeof(wndclass);
    wndclass.style=CS_HREDRAW|CS_VREDRAW;
    wndclass.lpfnWndProc=WndProc;
    wndclass.cbClsExtra=0;
    wndclass.cbWndExtra=0;
    wndclass.hInstance=hInstance;
    wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
    wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName=NULL;
    wndclass.lpszClassName=szAppName;
    wndclass.hIconSm=LoadIcon(NULL,IDI_APPLICATION);

    RegisterClassEx(&wndclass);

    hwnd=CreateWindow(szAppName,L"circle",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,
        CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL,hInstance,NULL);
    ShowWindow(hwnd,SW_MAXIMIZE);
    UpdateWindow(hwnd);
    SetTimer(hwnd,0,1,0);
    while(GetMessage(&msg,NULL,0,0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}
const int CENTER=300;
const int RADIUS=100;
LRESULT CALLBACK WndProc(HWND hwnd,UINT iMsg,WPARAM wParam,LPARAM lParam)
{
    HDC hdc;
    PAINTSTRUCT ps;
    static HDC wndDC=GetDC(hwnd);
    switch(iMsg)
    {
    case WM_CREATE:
        {
            MoveToEx(wndDC,CENTER+RADIUS,CENTER,0);
            mouse_event(MOUSEEVENTF_ABSOLUTE|MOUSEEVENTF_MOVE, (CENTER+RADIUS)*(65535.0/1366),(CENTER)*(65535.0/768),0,0);
            return 0;
        }
    case WM_PAINT:
        {
            hdc=BeginPaint(hwnd,&ps);
            EndPaint(hwnd,&ps);
            return 0;
        }
    case WM_MOUSEMOVE:
        LineTo(wndDC,LOWORD(lParam),HIWORD(lParam));
        return 0;
    case WM_TIMER:
        {
            srand(clock());
            static int count=0;
            for (int i=0;i<1000;i++)
            {
                count++;
                mouse_event(MOUSEEVENTF_ABSOLUTE|MOUSEEVENTF_MOVE, (CENTER+RADIUS*cos(2*M_PI*count/10000))*(65535.0/1366),
                    (CENTER+100*sin(2*M_PI*count/10000))*(65535.0/768),0,0);
            }
            if (count==10000)
                KillTimer(hwnd,0);
            return 0;
        }
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd,iMsg,wParam,lParam);
}

I expected to get circle but get decagon) I called mouse_event 10000 times in this program. Message WM_MOUSEMOVE was handled 10 times (same with timer). ie mouse_event calls (1000 times) weren't sended in message queue except for one from 1000. What is reason for it?

Answer 1

The WM_MOUSEMOVE message is a coalescing message. If a mouse_event happens and the application has not yet processed the previous mouse_event , then the previous one is thrown away. In your case, you generated 1000 mouse_events with no intervening message pump, so all but the last one gets thrown away.

Answer 2

        for (int i=0;i<1000;i++)
        {
            // etc...
        }

As I explained in your previous question, Windows can only call the hook callback when your thread is pumping the message loop. It is not doing any pumping while your code is executing inside this for() loop. As a result, Windows accumulates all the mouse events you generate into a single mouse move message. You'll get it when the for() loop exits.

Answer 3

Probably you call mouse_event after too short time interval. It depend from mouse threshold values in Win settings. You may probe manipulate SystemParametersInfo(...) with uiAction = SPI_GETMOUSE.

Eventually you may sychronize WM_MOUSEMOVE and mouse_event - send mouse_event after success with WM_MOUSEMOVE.