+void wxTopLevelWindowBase::DoCentre(int dir)
+{
+ // on some platforms centering top level windows is impossible
+ // because they are always maximized by guidelines or limitations
+ if(IsAlwaysMaximized())
+ return;
+
+ // we need the display rect anyhow so store it first
+ int nDisplay = wxDisplay::GetFromWindow(this);
+ wxDisplay dpy(nDisplay == wxNOT_FOUND ? 0 : nDisplay);
+ const wxRect rectDisplay(dpy.GetClientArea());
+
+ // what should we centre this window on?
+ wxRect rectParent;
+ if ( !(dir & wxCENTRE_ON_SCREEN) && GetParent() )
+ {
+ // centre on parent window: notice that we need screen coordinates for
+ // positioning this TLW
+ rectParent = GetParent()->GetScreenRect();
+
+ // if the parent is entirely off screen (happens at least with MDI
+ // parent frame under Mac but could happen elsewhere too if the frame
+ // was hidden/moved away for some reason), don't use it as otherwise
+ // this window wouldn't be visible at all
+ if ( !rectDisplay.Contains(rectParent.GetTopLeft()) &&
+ !rectParent.Contains(rectParent.GetBottomRight()) )
+ {
+ // this is enough to make IsEmpty() test below pass
+ rectParent.width = 0;
+ }
+ }
+
+ if ( rectParent.IsEmpty() )
+ {
+ // we were explicitely asked to centre this window on the entire screen
+ // or if we have no parent anyhow and so can't centre on it
+ rectParent = rectDisplay;
+ }
+
+ // centering maximized window on screen is no-op
+ if((rectParent == rectDisplay) && IsMaximized())
+ return;
+
+ // the new window rect candidate
+ wxRect rect = GetRect().CentreIn(rectParent, dir);
+
+ // we don't want to place the window off screen if Centre() is called as
+ // this is (almost?) never wanted and it would be very difficult to prevent
+ // it from happening from the user code if we didn't check for it here
+ if ( rectDisplay.Contains(rect.GetTopLeft()) )
+ {
+ if ( !rectDisplay.Contains(rect.GetBottomRight()) )
+ {
+ // check if we can move the window so that the bottom right corner
+ // is visible without hiding the top left one
+ int dx = rectDisplay.GetRight() - rect.GetRight();
+ int dy = rectDisplay.GetBottom() - rect.GetBottom();
+ rect.Offset(dx, dy);
+ }
+ //else: the window top left and bottom right corner are both visible,
+ // although the window might still be not entirely on screen (with
+ // 2 staggered displays for example) we wouldn't be able to
+ // improve the layout much in such case, so just leave it as is
+ }
+ else // make top left corner visible
+ {
+ if ( rect.x < rectDisplay.x )
+ rect.x = rectDisplay.x;
+
+ if ( rect.y < rectDisplay.y )
+ rect.y = rectDisplay.y;
+ }
+
+ // -1 could be valid coordinate here if there are several displays
+ SetSize(rect, wxSIZE_ALLOW_MINUS_ONE);
+}
+