Variable FillPanelConst

Remarks

Excel buries pattern and gradient fills in a desktop-only "Fill Effects" sub-dialog, and Excel Online drops them entirely: on the web, a cell's fill is a single color. The model here has always carried all three (IFill.Type.Solid | Pattern | Gradient), so this tab surfaces them as one choice — pick the KIND of fill, then edit that kind — rather than hiding two of the three behind a button.

IFill.Type.None is a fourth model type but not a fourth choice: it reads as Solid with the picker's No Fill swatch selected, the same swatch the ribbon offers. Setting a color was the common case and a No Fill entry in the type dropdown cost it an extra trip through that dropdown.

Every control here reads FormatSelection.style and writes through FormatSelection.applyStyle — solid included. The solid swatch used to be the ribbon's formatFillColor command button, which reads and writes the SHEET's selection directly: correct in the task pane, wrong the moment a caller hands these panels a selection of their own. The command is still consulted for the picker's cross-surface memory (last-used color, recent colors), just not for the value.