Updated September 2011
For XTREE controls with variable height items (XTF_VARY), specifies the maximum number of lines of text that will be displayed for a single item. For fixed height items (i.e. when then XTF_VARY flag is not specified), xtr'itemlines determines the display height of every row.
Setting xtr'itemlines = -1 (or 255) produces a row height equal to that needed for editable cells, which is typically about one and a half rows high. (This is automatic when the tree contains editable cells.)
Setting xtr'itemlines = -2 may be used to shrink the row height to match the largest cell font. (Otherwise, adjustments to the font scale typically don't affect the row spacing.)
History
2011 September, A-Shell 5.1.11233: Add support for -2 (see above)