Merge pull request #7363 from dotCooCoo/fix/stained-instance-export

Symbols: a stained instance keeps its stain in SVG, PDF and the other exports

docs/target-app-parity.md

@@ -940,6 +940,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - **Dynamic symbol appearance follows what an object draws** (VectorCraft's own rule): `symbol.instance.setAppearance` refuses a fill or stroke for an object of the art that does not draw it (a guide, blend, envelope, Repeat, Intertwine group, gradient mesh or placed document; a nested symbol instance's stroke, and its fill unless a solid color or none, which stains its art; an image's fill or stroke without a Convert to Shape or Outline Object effect) with an error that names the key and the object, and the call changes nothing. Opacity, blend and `null`, which takes a stored change back, are taken for every object. Tests: `crates/engine/src/tests/dynamic_symbols.rs`.
   - Symbol editing mode keeps every instance in step: instances of a dynamic symbol inside other symbols' art, pattern tiles, graph designs, stored brushes and opacity masks keep their appearance changes on the objects an edit reorders and drop the changes to objects it deletes. The view does not draw the instance the edit was entered from. Area type in the symbol's art takes the text wrap that moving a wrap object gives it. Editing another symbol at a place that fails keeps the current edit open, and only the editing layer or art on it can be isolated. Tests: `crates/engine/src/tests/symboledit.rs`, `isolation::symbol_editing_does_not_draw_the_instance_it_was_entered_from`, `panels::symbols::tests::double_clicking_a_symbol_in_the_panel_edits_it_in_either_view`, `the_panel_menus_edit_symbol_edits_the_instances_symbol_or_the_panels`, `the_control_bars_edit_symbol_edits_the_selected_instances_symbol`, `chrome::tests::the_control_bar_exits_symbol_editing_mode`.
   - **Dynamic symbol instances on the canvas** ([Symbols, archived copy](https://web.archive.org/web/20240206075757/https://helpx.adobe.com/illustrator/using/symbols.html)): each instance of a dynamic symbol can have an appearance of its own while it shares the symbol's shape. The rest of this entry is VectorCraft's own rules. A Direct Selection click on an instance of a dynamic symbol selects the path, compound path or type object of the symbol's art under the pointer and outlines it (`symbol.instance.selectPart`); the Swatches and Color panels, the Control bar, the Eyedropper and the other fill and stroke controls then change that object's fill or stroke (solid, none, gradient or pattern) for this instance only, each as one undo step, and `transparency.set` changes its opacity and blend the same way; the symbol's art and its other instances stay as they were. Alt or Shift picks the instance whole. An Eyedropper source that is not a path, compound path or type, a click on any other object of the art (a group, image, blend or nested instance) and the commands that change the selected objects (moving, Delete, Group, Hide, Lock, Arrange, Expand, the gradient annotator, isolate/knockout on Transparency, the Appearance panel's rows and others) are refused with a status message. Copy, Export Selection, Fit to Selection, Liquify, Isolate, Add to Library and Save Selection use the whole instance (`docs/mcp.md`), and another selection tool selects the instance whole again. Tests: `crates/engine/src/tests/dynamic_symbols.rs` (`gradients_and_patterns_on_a_picked_object_are_taken`, `opacity_and_blend_on_a_picked_object_go_through_transparency_set`), `direct::tests::a_click_on_a_dynamic_instance_picks_the_object_under_the_pointer`.
+  - **Stained symbol instances in export** ([the help page](https://web.archive.org/web/20220911143322/https://helpx.adobe.com/pdf/cs6/illustrator_reference.pdf#page=136), Stain symbol instances): an instance colored with the Symbol Stainer is exported in the colors the canvas draws it in. The mix is VectorCraft's own rule: after a dynamic symbol's own changes, the instance's visible fill mixes the solid fills and strokes of the symbol's art, type included, toward the fill's color by the fill's opacity; a hidden fill or one at 0% leaves the art's colors as they are. SVG, PDF (printing to PDF included), EPS, legacy `.ai`, DXF, EMF and WMF write the stained colors for an instance on its own, in a group, placed through 9-slice guides or reshaped by its geometry effects, and a color adjustment on the instance recolors the stained art. Tests: `bake::tests::a_stained_instance_is_baked_in_its_stained_colors` (vectorcraft-effects), `tests::a_stained_instance_keeps_its_stain` (vectorcraft-pdf), `symbols_layers::a_stained_instance_with_a_geometry_effect_keeps_its_stain` (vectorcraft-svg), and `a_stained_instance_is_written_in_its_stained_color` in vectorcraft-eps (EPS and legacy `.ai`), vectorcraft-cad and vectorcraft-metafile (EMF and WMF).
   - **9-slice guides on the canvas** ([public source](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/maintain-proportions-while-scaling-symbols.html)): while a symbol with Enable Guides for 9-Slice Scaling on is edited in symbol editing mode, the canvas draws its two horizontal and two vertical guides as dotted lines across its art, with any tool and with ruler guides hidden. With the Selection tool the pointer near a guide shows the Move cursor, and dragging the guide moves it (`symbol.options`'s `nineSliceGuides`) as one undo step; Escape during the drag puts it back. VectorCraft's own rules: a guide within 4 screen pixels takes the press before the art and the bounding box; it may pass the art's edges (see the next entry) and stops short of the opposite guide; the drag does not snap. Tests: `nineslice::tests`, `symbol_nine_slice::tests::the_edited_symbols_guides_cross_its_art_where_the_editing_layer_shows_it`, `a_moved_guide_passes_the_arts_edges_and_stops_short_of_the_opposite_guide`, `canvas::tests::the_edited_symbols_nine_slice_guides_are_drawn_and_dragged_on_the_canvas`.
   - **9-slice guides outside the art** ([the help page](https://help.adobe.com/archive/en/illustrator/cs6/illustrator_reference.pdf), Use 9-slice scaling section): a guide may lie outside the symbol's art, set by dragging it past the art's edge in symbol editing mode, by `symbol.options`'s `nineSliceGuides` or by a Symbol Options field below 0% or above 100%, and a scaled instance still scales, by the cells its art falls in. VectorCraft's own rules: each guide lies within 16 times the art's width or height of its edge (`-16..16` as a fraction, `-1600..1600` in percent) and the two guides of an axis keep their order; a guide past an edge of the art cuts the art at that edge, so the outer cell on its side holds no art; with both guides of an axis past opposite edges the art scales as a whole along it; with both past the same edge the art lies in the outer cell at the other edge and keeps its size, from that edge of the instance, or shrinks to the instance's width or height when the instance is smaller than the art; Symbol Options shows and keeps the guides unrounded. Native files keep the guides exactly; SVG and `.ai` write such an instance as its placed art and keep no guides. Tests: `symbol_nine_slice::tests::guides_outside_the_art_are_accepted_in_order_and_within_the_limit`, `art_scales_by_the_cells_it_falls_in_when_guides_lie_outside_it`, `the_map_with_guides_outside_the_art_is_continuous_and_monotone` in `crates/doc`, `guides_outside_the_art_are_set_by_command_and_scale_by_the_cells_that_hold_art`, `a_guide_dragged_past_the_arts_edge_lies_outside_it`, `guides_outside_the_art_survive_saving_and_reopening_a_native_file` in `crates/engine`, `nineslice::tests::a_guide_outside_the_art_is_taken_and_dragged_past_the_arts_edge`, `a_nine_slice_instance_with_a_guide_outside_its_art_is_written_as_drawn` (SVG and `.ai`).
   - **Delete Symbol asks first** ([Symbols panel](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/symbols-panel-options.html), [symbol libraries](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/create-or-import-symbol-libraries.html), [Alt-click Delete](https://helpx.adobe.com/illustrator/using/default-keyboard-shortcuts.html)): the Symbols panel's Delete Symbol button and menu item ask "Delete the selected symbol?" with Yes and No for a symbol no instance uses. For a symbol with placed instances they ask with Expand Instances (the instances become ordinary art), Delete Instances and Cancel; either Instances button deletes the symbol in one undo step. Alt-click on the button deletes an unused symbol without asking and still asks about one with instances. A question left open while another document became active deletes nothing. `symbol.delete` itself does not ask. Tests: `panels::symbols::tests::delete_symbol_asks_first_and_alt_click_deletes_an_unused_symbol_at_once`, `the_in_use_question_expands_or_deletes_the_instances`, `a_stale_delete_symbol_question_deletes_nothing`, `the_delete_symbol_questions_show_their_buttons`.