Brushes: drag a brush onto the canvas to place a copy of its art

A scatter, art or pattern brush dragged from the Brushes panel onto an
empty part of the canvas places a copy of its art there to edit,
centered where it is dropped (brush.placeArt). Dropped on a path, a
brush is still applied to it. A pattern brush is placed as its tiles in
a row, 10 pt apart, each in a group named for its tile, with an
unpainted rectangle at the back of a tile that has a repeat frame.
Calligraphic and bristle brushes have no art and are refused. A symbol
instance in the art is measured by its symbol's art.

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

docs/mcp.md

@@ -2895,6 +2895,15 @@ Brushes panel's New Brush button, its menu's New Brush… and art dropped on the
 Brush Options for the new brush; for a scatter, art or pattern brush they preview the art from `brush.selectionArt`.
 Their OK runs `brush.new {type, name, params, ids?}`, and Cancel adds no brush.
 
+`brush.placeArt {name, x?, y?}` places a copy of the art a scatter, art or pattern brush is made of, centered on
+(`x`, `y`) (default: the center of the first artboard), and selects it, in one undo step. The app runs it when a
+brush is dragged from the Brushes panel onto an empty part of the canvas; dropped on a path, a brush is applied to it
+(`brush.apply`). A pattern brush places its tiles left to right, 10 pt apart, in the order side, outer corner, inner
+corner, start, end (only the tiles it has art for), each in a group named Side Tile, Outer Corner Tile, Inner Corner
+Tile, Start Tile or End Tile. A tile with a repeat frame has an unpainted rectangle at the back of its group that marks
+the frame. A symbol instance in the art is measured by its symbol's art. A calligraphic or bristle brush is refused
+with "`<name>` has no art (only scatter, art and pattern brushes do)".
+
 `variable.bind`, `variable.unbind`, `variable.delete`, `dataset.set`, `dataset.update`, `dataset.delete`,
 `dataset.select`, `dataset.next` and `dataset.prev` add no undo step when they leave the document as it was, such as
 binding art to a variable it already has or applying the active data set again: the steps to redo stay, and a saved

docs/target-app-parity.md

@@ -1337,6 +1337,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     Document Info's Save… writes the category the panel shows, with Selection Only applied, as the [Document Info panel](https://helpx.adobe.com/illustrator/desktop/get-started/learn-the-basics/document-info-panel.html) page describes ("Exports the selected category's visible information to a text file"). With All Categories shown it writes every category, which is VectorCraft's own rule (`docInfo.save {category}`). Test: `panels::doc_info::tests::save_writes_the_category_the_panel_shows`.
     The Brushes panel menu's Select All Unused selects the brushes that are not used in the document, as the [Brushes](https://web.archive.org/web/20241230205225/https://helpx.adobe.com/illustrator/using/brushes.html) page (archived copy) describes. A brush counts as used when a stroke paints with it in the art (opacity masks included), in symbols, graph designs, pattern tiles or graphic styles, or in the art of a used brush (`brush.unused`).
     A rename in Brush Options and Delete Brush change every stroke that paints with the brush: in the layers and opacity masks, symbols, graph designs, pattern tiles, graphic styles and the art of other brushes. A rename gives those strokes the new name, and Delete Brush makes them plain strokes, in one undo step.
+    A scatter, art or pattern brush dragged from the Brushes panel onto an empty part of the canvas places a copy of its art there to edit, as the [Modify brushes](https://helpx.adobe.com/illustrator/desktop/paint-and-fill/apply-and-edit-strokes/modify-brushes.html) page describes (`brush.placeArt`). The copy is centered where it is dropped. A pattern brush comes out as its tiles in a row, 10 pt apart, each in a group named for its tile, with an unpainted rectangle at the back of a tile that has a repeat frame. The centering and the tile layout are VectorCraft's own rules. Evidence: `tests::brushsym::place_art_puts_a_copy_of_the_brush_art_where_it_is_dropped`, `tests::brushsym::pattern_brushes_place_their_tiles_in_a_row` (vectorcraft-engine), `canvas::tests::a_brush_with_art_dropped_off_the_art_places_a_copy_of_its_art_there` (vectorcraft-ui-egui).
     In Pattern Brush Options, a menu below the Outer Corner Tile and the Inner Corner Tile sets each to the brush's own corner art (Original), None, or a tile made from the side tile: Auto-Centered stretches one side tile around the corner, Auto-Between bends a side tile on each side into the corner's diagonal, Auto-Sliced cuts a side tile on each side along the diagonal, and Auto-Overlap runs a side tile on each side past the corner. Auto-Sliced masks the tiles at the diagonal, so their outlines stay as drawn. Brushes saved without these choices draw their corners as before (`brush.options` `outer_source`, `inner_source`). Evidence: `tests::pattern_auto_corners_fill_each_corner_of_a_square`, `tests::pattern_corner_source_none_leaves_that_kind_of_corner_empty` (vectorcraft-brush), `dialogs::brush_options::tests::pattern_options_set_each_corner_tile_to_original_none_or_an_automatic_tile` (vectorcraft-ui-egui).
 
     Pattern brush corner tiles are square to the side tiles at a right-angle corner and turn 90° from one corner to the next, as the [Using Illustrator CS5](https://help.adobe.com/archive/en_US/illustrator/cs5/illustrator_cs5_help.pdf) help (About patterns) describes. That document's steps for making corner tiles build both the outer and the inner tile as the corner joining a side tile on its right to one below it, and the brush reads corner art that way, with Flip Along and Flip Across or without (#6110). At corners that are not right angles, the tile is turned halfway between the two sides, which is VectorCraft's own rule. Evidence: `tests::pattern_corner_tiles_are_square_to_the_sides`, `tests::pattern_corner_tiles_sit_on_the_corners_diagonal` (vectorcraft-brush).