#277 TMDIClient::EvMDIDestroy steals focus and causes flicker

[Vidar Hasfjord]

Reported by Erwin Lotter (elotter):

A problem I face thereby occurs when the last TMDIChild of the active layer is closed. Then, severel of the hidden TMDIChilds get visible (blink up) for a short time (which depends on the number of the hidden TMDIChilds) and one of these hidden windows is activated (and receives the keyboard focus) [discussion:ff4f6b0b].

[Erwin Lotter]

When the last visible MDI child is removed, TMDIChild::EvNCActivate() does not work as expected.
In this case Windows forces the activation of a temporarily unhidden child and paints it's non-client area.
It seems that this occurs repeatedly when the children are rehidden after Destroy() is done. As a consequence, all hidden children blink up.
This can be prevented by implementing

void TMyMDIChild::EvNCPaint(HRGN hrgn) 
{
  if (!IsFlagSet(wfUnHidden)) {
    TMDIChild::EvNCPaint(hrgn);
  }
}

Alternatively, TMDIChild could be extended this way - with the risk of new side effects unknown yet.
Therefore, it might be the better strategy to document the problem and suggest this solution to those who hide MDI child windows.

[Erwin Lotter]

..., and EV_WM_NCPAINT needs to be added to the response table.

[Vidar Hasfjord]

Hi Erwin, thanks for the feedback on this issue. You are welcome to implement your fix on the trunk, so that we can gain experience with it in practice. We can then make a judgement on the robustness of your approach as we get closer to the release of version 7.

If you do decide to implement your fix, please take ownership of this ticket and set the milestone to version 7.

[Erwin Lotter]

Hi Vidar,

I'm not involved in the mysteries of trunks and branches. Could you
please handle this part?

Erwin

---

Moderator: Removed quoted content.