Plugin API requests

I want to make a support column plugin. The idea behind the plugin is the user clicks on the ground where they want the support column drawn, then drags up until the column is at the desired height. The user would also be able to set the colors of the support column. Custom scenery for support columns have been made in 3 positions: quarter-tile centered, half-tile centered, and full-tile centered. It would be nice to include all 3 options in the plugin.

Based on the current state of the Plugin API, I presume this would require some new things added:

• color picker UI element
• way to get what tile/half tile/quarter tile the mouse is on
• way to get what height the mouse is at for a given tile
• localized ghost objects to preview (ideally so they don't create desyncs if they are manipulated arbitrarily)
• turning on the virtual floor
• onClose for Window (so the virtual floor can be turned off if the window is closed unexpectedly)
• image button (to rotate cross-members)

Start by reviewing the current Plugin API and the requested support-column workflow. Identify which listed capabilities are missing, including color selection, tile and height queries, ghost previews, virtual-floor control, and window-close handling. Done means the API supports the complete interactive workflow and the three support-column positions without desyncs.