Can i track my mouse pos outside a SDL window?

Question

I build a clock with SDL, its a window without border. Now i still wanna be able to move my clock around my screen so i wrote a function to move it. Basicly it waits for an mousedown input and then calculates the distance moved till u release the mouse. Then it moves the window. The Problem is that it only gets mousepos INSIDE my clock window, so i can just move it barely if i click the upper left and then slide to the lower right corner of my clock window.

sPos moveClock(int event){
    if(event==-1&&mPos.x==0&&mPos.y==0){
        mPos = setPos(gvMousePos.x,gvMousePos.y);
        cout << "down" << endl;
    }
    if(event==-65){
        mPos = setPos(gvMousePos.x-mPos.x,gvMousePos.y-mPos.y);
        cout << "up" << endl;
        sPos temPos = mPos;
        mPos = setPos(0,0);
        return temPos;
    }
    return setPos(0,0);
}

I would like to be able to move my clock anywhere on the screen so i need a way to get my mousepos even outside the window. Or a way to calc the distance while mousedown even if i move outside the SDL created window.

Answer 1

SDL_CaptureMouse():

\brief Capture the mouse, to track input outside an SDL window.

\param enabled Whether or not to enable capturing

Capturing enables your app to obtain mouse events globally, instead of just within your window. Not all video targets support this function. When capturing is enabled, the current window will get all mouse events, but unlike relative mode, no change is made to the cursor and it is not restrained to your window.

This function may also deny mouse input to other windows--both those in your application and others on the system--so you should use this function sparingly, and in small bursts. For example, you might want to track the mouse while the user is dragging something, until the user releases a mouse button. It is not recommended that you capture the mouse for long periods of time, such as the entire time your app is running.

While captured, mouse events still report coordinates relative to the current (foreground) window, but those coordinates may be outside the bounds of the window (including negative values). Capturing is only allowed for the foreground window. If the window loses focus while capturing, the capture will be disabled automatically.

While capturing is enabled, the current window will have the SDL_WINDOW_MOUSE_CAPTURE flag set.

\return 0 on success, or -1 if not supported.

extern DECLSPEC int SDLCALL SDL_CaptureMouse(SDL_bool enabled);

Answer 2

SDL_GetGlobalMouseState() is likely what you need:

/**
 * Get the current state of the mouse in relation to the desktop.
 *
 * This works similarly to SDL_GetMouseState(), but the coordinates will be
 * reported relative to the top-left of the desktop. This can be useful if you
 * need to track the mouse outside of a specific window and SDL_CaptureMouse()
 * doesn't fit your needs. For example, it could be useful if you need to
 * track the mouse while dragging a window, where coordinates relative to a
 * window might not be in sync at all times.
 *
 * Note: SDL_GetMouseState() returns the mouse position as SDL understands it
 * from the last pump of the event queue. This function, however, queries the
 * OS for the current mouse position, and as such, might be a slightly less
 * efficient function. Unless you know what you're doing and have a good
 * reason to use this function, you probably want SDL_GetMouseState() instead.
 *
 * \param x filled in with the current X coord relative to the desktop; can be
 *          NULL
 * \param y filled in with the current Y coord relative to the desktop; can be
 *          NULL
 * \returns the current button state as a bitmask which can be tested using
 *          the SDL_BUTTON(X) macros.
 *
 * \since This function is available since SDL 2.0.4.
 *
 * \sa SDL_CaptureMouse
 */
extern DECLSPEC Uint32 SDLCALL SDL_GetGlobalMouseState(int *x, int *y);

It fills x and y with global mouse position and returns the current mouse button state.