Tooltips: what a button without words says on hover (#209)

Architecture has the paragraph on the tooltip layer and its rule, Concepts names the tooltips of the top bar, Development carries the sum of 1667 e2e checks.

Architecture.md

@@ -40,6 +40,23 @@
   so the stage is nudged by 1/32 px (`tieBreakFor`), which sends every tie the same way.
   What this does not give is the subpixel smoothing a browser applies to its own text: Pixi draws
   a text into a transparent picture first, and there only greyscale smoothing is possible.
+  **Tooltips** (#209). A `Button` takes a `tooltip` — a text, or a function asked each time — and
+  shows it on a small sign once the pointer has rested on it for half a second. A button without
+  one says its own label where that had to be cut short, which is how a tab with a long name shows
+  the whole of it. There is one sign for the whole page (`tooltips`, a `TooltipLayer` in
+  `ui/widgets/Tooltip.ts`), on the overlay above the menus: a control reports each pointer move
+  over itself (`point`) and the pointer leaving (`leave`), the layer does the waiting. A press, a
+  key or the wheel takes the sign away (`initUI` listens on the window), and the control stays
+  quiet until the pointer has left it. `placeTooltip` in `ui/tooltip.ts` is the rule for the
+  place, a pure function: under the control and flush with its left edge, flush with its right
+  edge where the sign would leave the screen on the right, above the control at the bottom.
+  A widget that draws its own marks reports them the same way with a key per mark — the eye, the
+  duplicate mark, the cross and the plus of a `SortableList`. What a sign says is decided where
+  the button is made: `toolbarTip` for the top bar ("Undo Paint tiles (Ctrl+Z)", from
+  `CommandStack.undoLabel`), `rowActionTip` for the row actions of the inspector (the one thing a
+  click would do, or the name of the group once it opens a menu). A button that is greyed out
+  takes no pointer events and so shows no sign. `__gm.tooltip()` reports the sign on screen with
+  its box and the box of its control; the text hooks (`locate`, `has`) do not see it.
   Double-clicks are counted in `clicks.ts`, not read off the event: Pixi only puts a click count
   on the `click` it synthesises and leaves `detail` at 0 on `pointerdown`, so every press handler
   that trusted `e.detail` never saw a second click. Presses are counted per key rather than per
@@ -248,7 +265,7 @@ src/editor/panels/     AssetPanel, assetGroups (groups by type and their order,
                        plus the List, Game, Plugins and User management tabs' own four, which stand for no asset),
                        assetMenu (the two groups of the + menu), HierarchyPanel + hierarchyDrop (#241: what
                        dropping a row does, group rows included) + GroupNameDialog,
-                       Toolbar + toolbarIcons (icon buttons, no captions: menu, undo, redo, play, pause, #183, and the eye
+                       Toolbar + toolbarIcons + toolbarTips (icon buttons, no captions: menu, undo, redo, play, pause, #183, what each says as a tooltip, #209, and the eye
                        the scene tab's header wears, see ScenePane),
                        SceneVisibilityPopup (behind the eye: symbol, name and collider outline per type),
                        headerIcons (the pictures of the tab headers' switches: the magnet, #194),

Concepts.md

@@ -156,7 +156,10 @@ as the Game tab in its top right corner (#267); a click on it never reaches the
 **menu** (three bars) on the left with *New project*, *Open project…*, *Snapshots…*, *Release…* and *Project settings…*,
 **undo** and **redo** beside it, and **play** and **pause** in the middle — on the middle of the
 window, not of the space the row has left over — where play turns into a stop square while a run is
-on, and pause into a second play sign while it is held. On the right stand the
+on, and pause into a second play sign while it is held. Rest the pointer on one of them and a
+**tooltip** says what it does and which keys do the same (#209); undo and redo name the step they
+would take, as in *Undo Paint tiles (Ctrl+Z)*. Every other button that carries a picture instead
+of words has one too, and a tab whose name was cut short shows the whole name. On the right stand the
 notice line, the save status, the frame rate and the **Account** menu. What the bar used to spell
 out lives in the menu now: the project list in *Open project…*, the project name, the
 **start-scene switch** (*Start scene* / *Active scene*, see **Start scene**), the **While playing**

Development.md

@@ -18,7 +18,7 @@ php tests/php/accounts.test.php                               # the API's accoun
                                                               #   has and the web server's container has not (SKIP there)
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1664 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1667 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result