How to automate Drag&Drop using SendInput - c++

Question

I want to test a flash application running on browser. I need to drag pieces around in the application. I want to do this by simulating mouse movements using windows api.
Here is my navie solution to simulate a mouse drag:
void MoveMouse(LPINPUT input, int x, int y) {
input->type = INPUT_MOUSE;
input->mi.dx = x*(65536/GetSystemMetrics(SM_CXSCREEN));
input->mi.dy = y*(65536/GetSystemMetrics(SM_CYSCREEN));
input->mi.dwFlags = MOUSEEVENTF_ABSOLUTE | MOUSEEVENTF_MOVE;
}
void LeftDownMouse(LPINPUT input, int x, int y) {
input->type = INPUT_MOUSE;
input->mi.dx = x*(65536/GetSystemMetrics(SM_CXSCREEN));
input->mi.dy = y*(65536/GetSystemMetrics(SM_CYSCREEN));
input->mi.dwFlags = MOUSEEVENTF_LEFTDOWN;
}
void LeftUpMouse(LPINPUT input, int x, int y) {
input->type = INPUT_MOUSE;
input->mi.dx = x*(65536/GetSystemMetrics(SM_CXSCREEN));
input->mi.dy = y*(65536/GetSystemMetrics(SM_CYSCREEN));
input->mi.dwFlags = MOUSEEVENTF_LEFTUP;
}
void DragMouse(LPINPUT inputs, int startX, int startY, int dropX, int dropY) {
MoveMouse(&inputs[0], startX, startY);
LeftDownMouse(&inputs[1], startX, startY);
LeftUpMouse(&inputs[2], startX, startY);
LeftDownMouse(&inputs[3], startX, startY);
MoveMouse(&inputs[4], dropX, dropY);
LeftUpMouse(&inputs[5], dropX, dropY);
}
int _tmain(int argc, _TCHAR* argv[])
{
INPUT inputs [6] = {};
// Assume there is a maximized window, mouse drags the window from 40, 10 to 100,100 coordinates.
DragMouse(inputs, 40, 10, 100, 100);
SendInput(6, inputs, sizeof(INPUT));
Sleep(1000);
return 0;
}
This code mostly doesn't work, sometimes works, it has undefined behaviour. What could be the problem? How can i solve this?

Answer 1

I had a similar problem with drag and drop, although my results were consistent in that the mouse was moving but not the item being dragged.
Your MoveMouse function is missing the MOUSEEVENTF_LEFTDOWN flag. Try input->mi.dwFlags = MOUSEEVENTF_ABSOLUTE | MOUSEEVENTF_MOVE | MOUSEEVENTF_LEFTDOWN;
Without the flag setting you are just asking the mouse to move without the left mouse button being down.
Edit
I just checked my implementation and I don't set coordinates when pressing or releasing the mouse buttons. Only when moving.
As for variance in results, you may stop these by zeroing out the INPUT before setting fields.