Pack locations refer to how an control will move its own location in relation to it's parent's bounds. Though I cannot say that I understand what "right,bottom" would mean because that doesn't follow the format the UI builder documentation specifies. It leaves out information and uses different keywords.
If you wanted a button to remain centered near the bottom within a resizable window, you could use "CPC,FFF". I think. This is sort of going off of memory of how it works.
It stands for this:
- C - Center horizontal point of the child control
- P - Proportionally (like a percentage) relocated
- C - Based on the Center of the parent control
- F - The Far vertical edge of the child control
- F - Using a Fixed (number of pixels) relationship to the parent control's edge
- F - Using the Far edge of the parent control
Regardless of the above, you still must set the location of the control in pixels to be positioned in the center of the parent control. (Still based on the upper-left corner of the child control) You cannot give locations as a wildcard.