[PATCH] winex11: The correct way to search the target window for drag&drop operations.

[John Found]

On Wed, 17 Apr 2019 18:30:11 -0500
Zebediah Figura <z.figura12 at gmail.com> wrote:

> Hello John, thanks for the patch! Note that all patches require a 
> Signed-off-by header, as a way of taking responsibility for the patch 
> and acknowledging that you believe it's acceptable for Wine.
> 
Hello Zebediah. I though it is needed only if I am posting a patch written by someone else.
But yes, I beleave, that this patch is acceptable and Wine. That is why I am sending it here.

Should I resend the patch again now, with this header?


> On 4/17/19 4:20 PM, John Found wrote:
>  > +/* the recursive worker for window_from_point_dnd */
>  > +HWND do_window_from_point_dnd(HWND hwnd, POINT* point)
>  > +{
>  > +    HWND w;
>  > +    w = ChildWindowFromPointEx(hwnd, *point, CWP_SKIPDISABLED | 
> CWP_SKIPINVISIBLE);
>  > +    if (w && (w != hwnd))
>  > +    {
>  > +        MapWindowPoints(hwnd, w, point, 1);
>  > +        w = do_window_from_point_dnd(w, point);
>  > +    }
>  > +    return w;
>  > +}
>  > +
>  > +
>  > +/* Recursively search for the window on given coordinates in a 
> drag&drop specific manner. */
>  > +HWND window_from_point_dnd(HWND hwnd, POINT point)
>  > +{
>  > +    POINT p;
>  > +    p.x = point.x;
>  > +    p.y = point.y;
>  > +    ScreenToClient(hwnd, &p);
>  > +    return do_window_from_point_dnd(hwnd, &p);
>  > +}
>  > +
> 
> Maybe I'm missing something here, but don't these two functions 
> effectively do the equivalent of WindowFromPoint(point)? Is there any 
> reason we can't just use that instead?
> 
> 
WindowFromPoint, ChildWindowFromPointEx and other similar functions return only the top level windows 
or the immediate children of them. While the drop target can be somewhere deeper in the window tree.
This is exactly why the behavior of drag&drop operations in Wine for Linux is different from the original Windows.

The function "do_window_from_point_dnd" searches recursively down the windows tree and returns the most deeper child that
contains the point. Then it searches back up, until a window with WS_EX_ACCEPTFILES is found. (or not, of course).


-- 
John Found <johnfound at asm32.info>