Objects on Path: the Space widget spaces the attached objects along the path

With one Objects on Path group of two or more objects selected, the
Selection and Objects on Path tools show a square Space widget beyond the
last object, ahead along the path. Dragging it moves the last object
along the path, around its bends, as far as the pointer moves along it,
and the objects between follow evenly while the first one stays. With
Alt (Option on macOS) the objects spread from both ends toward or away
from the center of an open path, or of the first anchor of a closed one.
The distance between the objects shows next to the pointer in the
document's units; the drag is one undo step, and Escape cancels it.

- object.objectsOnPath.options takes spacing (points, or "auto", the
  default even spread) and start (points from the first anchor). A
  spacing the path has no room for is drawn smaller and kept, so a
  longer path brings it back. Older files read as Auto.
- Moving the group, Pivot, Rotate, path edits, copies and saving keep
  the Space. Scaling, rotating or shearing the group keeps the first
  and last objects where the transform takes them on the new path, live
  shapes included; a value that cannot be kept that way scales with the
  path's length.
- The Rotate All widget follows the first object when Space moves it.

Behavior: https://helpx.adobe.com/illustrator/desktop/manage-objects/arrange-objects/rearrange-and-edit-objects-on-a-path.html
and https://helpx.adobe.com/illustrator/using/objects-on-path.html.

docs/mcp.md

@@ -6055,12 +6055,22 @@ attaches nothing.
 The group stays live: after every edit its objects go back on its path. Editing the path moves them, an object moved
 on its own goes back to its place, an object moved into the group (`layer.move` with `place: "inside"`) joins the end
 of the path, an object moved out of it leaves, and art that replaces an object (`symbol.breakLink`) keeps its place.
-`object.objectsOnPath.options {ids?, pivot?, rotate?}` changes Pivot and Rotate, and
+`object.objectsOnPath.options {ids?, pivot?, rotate?, spacing?, start?}` changes Pivot, Rotate and Space, and
 `object.objectsOnPath.expand {ids?}` makes the groups plain groups. Both act on the groups that `ids` names (Objects
 on Path groups or objects in them), or on the groups of the selection when `ids` is not given. The native file keeps
 the group with an `objects_on_path` record; SVG, PDF and the other exports write the path and the objects as plain
 art.
 
+Space sets the distance along the path between neighboring objects' attachment points. `spacing` takes points, 0 or
+more, or `"auto"`, the default, which spreads the objects evenly with the last one at the end of an open path. `start`
+is the distance in points along the path from its first anchor to the first object's attachment point (default 0). A
+`spacing` larger than the path has room for is drawn smaller: on an open path the last object stops at the end, and on
+a closed path the objects go no more than once around. The value is kept, so lengthening the path again brings the
+objects back to it. On a closed path, `start` counts around from the first anchor. Pivot, Rotate, moving the group and
+saving the file keep the Space. Scaling, rotating or shearing the group keeps the first and last objects where the
+transform takes them on the new path, and sets `spacing` and `start` to match; a value that cannot be kept that way
+scales as much as the path's length.
+
 In the desktop app, double-clicking the Objects on Path tool (`tool.options {tool: "objectsOnPath"}`) opens Objects on
 Path Tool Options (dialog `objectsOnPathOptions`): the nine-point Pivot grid and the Rotate field (°). Save sets the
 tool's options (`tool.setOption {tool: "objectsOnPath", values: {pivot, rotate}}`), which the objects attached next
@@ -6075,10 +6085,20 @@ counter-clockwise on the page: the drag previews `object.objectsOnPath.options {
 group's Rotate plus that angle and keeps it as one undo step on release. Shift turns in steps of 15°, and Escape
 cancels the drag.
 
+With two or more objects in the group, the same tools show the Space widget, a square handle beyond the group's last
+object, ahead along the path and joined by a line to its attachment point. Dragging it moves the last object along the
+path as far as the pointer moves along the path, and previews
+`object.objectsOnPath.options {ids: [group], spacing, start}` and keeps it as one undo step on release. The first
+object stays where it is and the others move toward or away from it; on an open path the last object goes no further
+than the end. With Alt (Option on macOS) held, the objects spread from both ends toward or away from the center of an
+open path, or of the first anchor of a closed path, up to the whole path. With measurement labels on, the distance
+between the objects shows next to the pointer in the document's units. Escape cancels the drag.
+
 ```json
 {"name":"run_command","arguments":{"command":"tool.setOption","params":{"tool":"objectsOnPath","values":{"pivot":7,"rotate":30}}}}
 {"name":"run_command","arguments":{"command":"object.objectsOnPath.attach","params":{"path":30,"ids":[12,15,18]}}}
 {"name":"run_command","arguments":{"command":"object.objectsOnPath.options","params":{"pivot":7,"rotate":15}}}
+{"name":"run_command","arguments":{"command":"object.objectsOnPath.options","params":{"spacing":24,"start":0}}}
 {"name":"run_command","arguments":{"command":"object.objectsOnPath.expand","params":{}}}
 ```
 

docs/target-app-parity.md

@@ -978,7 +978,8 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   When the object the Blend tool picked first is deleted or undone away before the second click, the next click on an object picks that object first instead of doing nothing. Regression tests: `blend_tool_picks_again_when_its_first_pick_is_gone` in `meshblend.rs` and `the_blend_tool_picks_again_when_its_first_pick_is_deleted` in `tests/blendopts.rs`.
   Window › Blend opens the Blend panel: Make, the selected blend's Spacing and Orientation (with no blend selected, the options new blends start with), Reverse Front to Back, Reverse Spine, Replace Spine, Expand and Release, each running its Object › Blend command. Make is dimmed until two or more objects are selected. Spacing and Orientation are dimmed until a blend or two or more objects are selected, and the other buttons are dimmed until a blend is selected.
   With the Blend tool, Escape drops the object clicked first and stops the next click adding to the blend just made, so the next click picks a new first object; the document and the selection stay as they are. Regression tests: `escape_drops_the_blend_tools_first_pick` in `meshblend.rs` and `tests/blendopts.rs`.
-  Objects on Path (#2545): a click with the Objects on Path tool (in Edit Toolbar's Modify section and the Blend tool's flyout; Object › Objects on Path › Attach and the context menu with two or more objects selected choose it) attaches the selected objects to the path clicked, open or closed, in an Objects on Path group with the path at its bottom. The objects go along the path column by column from left to right, spread evenly from its first anchor (the last one sits on the end of an open path), each turned to the path at its attachment point; Pivot and Rotate set where each one attaches and how far it tilts (`object.objectsOnPath.attach`, `object.objectsOnPath.options`), and with Objects on Path groups selected the Properties panel's Objects on Path Options section shows them as a nine-point Pivot grid and a Rotate field with common angles, each change one undo step for every selected group. Editing the path moves the objects, an object moved on its own goes back, objects moved into or out of the group in the Layers panel join or leave the path, and Object › Objects on Path › Expand leaves a plain group. The group saves and reopens live and exports as plain art. With one Objects on Path group selected, the Selection and Objects on Path tools show the Rotate All widget beside its first object: dragging it turns every object about its attachment point by the angle the pointer turns, adding it to the group's Rotate in one undo step, in 15° steps with Shift ([Objects on Path](https://helpx.adobe.com/illustrator/using/objects-on-path.html)). The Space, Move All and Select/Move widgets and Detach are missing.
+  Objects on Path (#2545): a click with the Objects on Path tool (in Edit Toolbar's Modify section and the Blend tool's flyout; Object › Objects on Path › Attach and the context menu with two or more objects selected choose it) attaches the selected objects to the path clicked, open or closed, in an Objects on Path group with the path at its bottom. The objects go along the path column by column from left to right, spread evenly from its first anchor (the last one sits on the end of an open path), each turned to the path at its attachment point; Pivot and Rotate set where each one attaches and how far it tilts (`object.objectsOnPath.attach`, `object.objectsOnPath.options`), and with Objects on Path groups selected the Properties panel's Objects on Path Options section shows them as a nine-point Pivot grid and a Rotate field with common angles, each change one undo step for every selected group. Editing the path moves the objects, an object moved on its own goes back, objects moved into or out of the group in the Layers panel join or leave the path, and Object › Objects on Path › Expand leaves a plain group. The group saves and reopens live and exports as plain art. With one Objects on Path group selected, the Selection and Objects on Path tools show the Rotate All widget beside its first object: dragging it turns every object about its attachment point by the angle the pointer turns, adding it to the group's Rotate in one undo step, in 15° steps with Shift ([Objects on Path](https://helpx.adobe.com/illustrator/using/objects-on-path.html)). The Move All and Select/Move widgets and Detach are missing.
+  Objects on Path Space widget: with one Objects on Path group of two or more objects selected, the Selection and Objects on Path tools show a square handle beyond its last object; dragging it along the path, round its bends, sets the distance between the objects' attachment points in one undo step, the first object staying where it is, and with Alt (Option on macOS) the objects spread from both ends toward the center; the distance shows next to the pointer during the drag, in the document's units ([Rearrange and edit objects on a path](https://helpx.adobe.com/illustrator/desktop/manage-objects/arrange-objects/rearrange-and-edit-objects-on-a-path.html), [Objects on Path](https://helpx.adobe.com/illustrator/using/objects-on-path.html)). The group keeps the distance (`object.objectsOnPath.options {spacing, start}`) through Pivot and Rotate changes, path edits, copies, saving and reopening, and scales it with the group; by default (`"auto"`) the objects are spread evenly as before. Evidence: `objects_on_path::tests::{space_sets_the_distance_between_the_stops, space_on_a_closed_path_wraps_at_the_first_anchor_and_stops_short_of_the_first_object}` in `crates/doc`, `tests::objects_on_path::space_sets_the_distance_between_the_objects_in_one_undo_step` in `crates/engine`, `objects_on_path::tests::dragging_the_space_widget_spaces_the_objects_from_the_first_one` in `crates/tools`.
   Double-clicking the Objects on Path tool opens Objects on Path Tool Options ([Objects on Path](https://helpx.adobe.com/illustrator/using/objects-on-path.html)): the nine-point Pivot grid and the Rotate field set the attachment point and angle of the objects attached next, and groups already attached keep theirs; Reset puts the center and 0° back. Save keeps the options across tool switches and saves them with the preferences (`tool.setOption {tool: "objectsOnPath"}`).
 - **Paint and appearance (M3):**
   - **CSS swatch libraries:** fractional linear and radial gradient stop positions are preserved, so nearby stops such as 12.5% and 12.890625% remain distinct instead of collapsing to 13%. Reference: [CSS Images 3 color stops](https://www.w3.org/TR/css-images-3/#color-stop-syntax). The original synthetic regression is `palette_io::tests::css_preserves_fractional_gradient_stop_positions` in `crates/color/src/palette_io.rs`. Scores and hours are unchanged.