Align: Distribute Objects uses the spacing value with a key object

With a key object, the Align panel's six Distribute Objects buttons
ignored the Distribute Spacing value. They kept the outermost objects
in place, spaced the others evenly between them and could move the
key object.

object.distribute now takes spacing. While the selection has a key
object, the key object stays in place, with the compound path or
selected group that contains it, and the objects' left edges, centers
or right edges (top edges, centers or bottom edges) end up spacing
points apart, outward from the key object's, in their order on that
line. With 0, the field's default, every object ends on the key
object's line. Two objects are enough, and to and artboard are not
used. The panel sends the value with the Distribute Objects buttons
while there is a key object, as it does with the Distribute Spacing
buttons. Without a key object, or with anchor points selected,
object.distribute does not use spacing and works as before. A spacing
that is not a number is an error.

Docs: docs/mcp.md, docs/target-app-parity.md.

docs/mcp.md

@@ -1807,9 +1807,17 @@ evenly by that line between them, and two objects are enough. `object.distribute
 left or top edge of the first object, in the order of those edges, on the artboard's left or top edge, and it puts the
 right or bottom edge of the last object on the artboard's right or bottom edge, with equal gaps between the objects.
 With `to: "selection"` or `"key"`, or without `to`, `object.distribute` and `object.distributeSpacing` without `spacing`
-keep the first and last objects where they are, and `object.distribute` moves nothing with fewer than three objects.
-With `spacing`, `object.distributeSpacing` does not use `to`. With anchor points selected (Direct Selection), both
-commands space the points among themselves and do not use `to` or `artboard`.
+keep the first and last objects where they are, and `object.distribute` without `spacing` moves nothing with fewer than
+three objects. With `spacing`, `object.distributeSpacing` does not use `to`, and `object.distribute` does not use it
+while the selection has a key object. With anchor points selected (Direct Selection), both commands space the points
+among themselves and do not use `to` or `artboard`.
+
+`object.distribute {spacing}` (the Distribute Objects buttons while the selection has a key object, `select.key`) keeps
+the key object where it is, with the compound path or selected group that contains it. It places the objects' lines
+(left edges, centers or right edges; top edges, centers or bottom edges) `spacing` points apart, outward from the key
+object's line, in their order on that line. With `spacing: 0`, every object ends on the key object's line. Two objects
+are enough. Without a key object, or with anchor points selected, `object.distribute` does not use `spacing`. A
+`spacing` that is not a number is an error.
 
 The desktop app adds its active artboard, the one the Artboards panel highlights, to the `object.align`,
 `object.distribute`, `object.distributeSpacing` and `select.allOnArtboard` calls it runs without `artboard`, as it does

docs/target-app-parity.md

@@ -509,6 +509,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   Choosing the Artboard tool (Shift+O, its toolbar button, or Edit Artboards in Properties or Document Setup) starts it on the active artboard: the canvas outlines that artboard, and Delete, Cut, Copy, the Transform panel and Artboard Options act on it.
   In the Artboards panel, a click on the active artboard's options icon, or a double-click on another row's icon, opens Artboard Options for that row's artboard, and the panel menu's Artboard Options… opens it for the active artboard (part of #1876). Both used to choose the Artboard tool instead. Opened while another tool is in use, the dialog moves the art with a new X or Y when the Artboard tool's Move Artwork with Artboard option is on.
   With Align to Artboard chosen, the Align panel's Distribute Objects and Distribute Spacing buttons use the active artboard (`object.distribute` and `object.distributeSpacing` with `to: "artboard"` and `artboard`). The first object's left or top edge goes to the artboard's left or top edge, and the last object's right or bottom edge goes to the artboard's right or bottom edge. Distribute Objects spaces the other objects evenly by its button's line, and two objects are enough. Distribute Spacing makes the gaps between the objects equal. With anchor points selected, the buttons space the points among themselves and do not use the artboard. When an action plays, its Distribute Objects and Distribute Spacing steps with Align to Artboard use the artboard that is active then.
+  With a key object, the Align panel's Distribute Objects buttons use the Distribute Spacing value (`object.distribute {spacing}`): the key object, or the compound path or selected group that contains it, stays in place, and the objects' left edges, centers or right edges (top edges, centers or bottom edges) end up that far apart, outward from the key object's, in their order. With the field's default value of 0, a click puts every object on the key object's line (behavior reference: [Ask Mordy: Distributing Objects](http://rwillustrator.blogspot.com/2008/01/ask-mordy-distribute.html)).
   Choosing the Artboard tool (Shift+O, its toolbar button, Edit Artboards in Properties or Document Setup, or the Artboards panel menu's Artboard Options…) starts it on the active artboard: the canvas outlines that artboard, and Delete, Cut, Copy, the Transform panel and Artboard Options act on it.
   Object › Artboards › Fit to Artwork Bounds and Fit to Selected Art resize the active artboard, as the Artboards panel menu's Fit to Artwork Bounds does (`artboard.fitToArt {index}`, `artboard.fitToSelection {index}`). They used to resize artboard 1 whichever artboard was active. When an action plays, its Fit to Artwork Bounds and Fit to Selected Art steps that name no artboard resize the artboard that is active then.
   The canvas draws the active artboard's edge in black, as the public [Select artboards](https://helpx.adobe.com/illustrator/desktop/create-manage-artboards/add-edit-artboards/select-artboards.html) page describes. It draws the other artboards' edges in gray. With several artboards selected by the Artboard tool, the canvas draws the black edge around the active one, which the tool shows with handles and its name. It used to draw artboard 1's edge in black whichever artboard was active.