Please describe the problem:
I first noticed this when using the "autofill" feature in a document with a few thousand rows: I didn't see any tooltip showing me the value of the last cell to be filled. At first I thought perhaps the feature had been disabled, or only worked for some cases, but then I noticed that it still worked in smaller documents.

It turns out that (for me) up to the 900th row or so, the tooltip is positioned near the selected rectangle, as expected. Somewhere near the 1000th row, the Y position of the tooltip increases rapidly, to the point that before I reach the 1030th row, the tooltip is no longer visible on my screen.

The same thing also happens for tooltips on hyperlinks. I'll use that case when describing how I can reproduce it.

Steps to reproduce:
1. All we need is an empty spreadsheet, so simply start Gnumeric.
2. Scroll down to the around the 1000th row.
3. Create a hyperlink in a cell, and give it a tooltip.
4. Let the mouse hover above the tooltip.


Actual results:
The tooltip appears at the correct X position, but too far down. Possibly outside the screen. If it doesn't work, repeat steps 3-4 further down in the document.

Expected results:
I would expect the tooltip to appear close to the mouse pointer or, in the case of autofill, near where the cursor was when I began autofilling.

Does this happen every time?
Yes. I can't give you the exact row number where it starts to happen, so I guess it might actually depend on how far down I've scrolled the document, rather than the row number.

Other information:
I'm running "unstable" Debian, though the problem happens both with Debian's Gnumeric packages and if I compile it myself. I haven't tried compiling any of the supporting libraries myself, though.

The position of the tooltip is calculated like this:

	GtkWidget *cw = GTK_WIDGET (FOO_CANVAS_ITEM (ic)->canvas);
	GdkWindow *cbw = GTK_LAYOUT (cw)->bin_window;
	int wx, wy;
	gdk_window_get_origin (cbw, &wx, &wy);

This particular snippet is from item_cursor_tip_setlabel(), though it's used in a couple of other places.

I don't know if this is a Gnumeric (1.9.9) problem, a GTK+ (2.16.2) problem, or somewhere in between. I believe this "foo canvas" thing is a part of libgoffice (0.7.8).