I'm working on an intellisense or code-completion capability for C#.

So far, so good. Right now I have basic completion working. There are 2 ways to request completion. The first cycles through all the potential matches. The second presents a popup menu of the matches. It works for types:

And also for local variables:

I'm confronting two problems with x-popup-menu:

1. the popup menu can expand to consume all available screen space, when the number of choices is large. Literally it can obscure the entire screen. The silly thing is, it's scrollable. First it expands to consume all available space, then it also becomes scrollable. Is there a way I can limit the maximum size of x-popup-menu?
2. To specify the position of the popup menu, I pass in a position, and x-popup-menu uses that as the *middle*, not the left, of the top line of the menu. Why middle? who knows. What this means is, if I specify (40 . 60) for the location of the menu, and the menu happens to be 100 pixels wide, the menu will extend beyond the left border of the emacs window. You can see this in the 2nd image above. If I knew how wide the popup would be before specifying the position, I could compensate. But I don't. Is there a workaround? Is there a way to get x-popup-menu to take its position as the LEFT rather than the middle.