Add text labels: click to type on the board

[marcosqlbi]

Closes #132, the fourth pull request of the 1.6.0 design objects plan
(docs/design-objects.md).

Why

A whiteboard needs a word written on it as often as it needs a drawing of one:
a heading over a sketch, a name beside an arrow, a note that has to be legible
in a recording. Until now the only text a board could hold was a pasted-code
container, with a title bar and a language, which is the wrong object for two
words over a diagram. A label is the other one: click, type, and it is on the
board with the font, size, color, style, and quarter turn you last used.

What it affects

• The model. FreeTextBoardObject joins BoardObjects.cs as a container:
  its layout rectangle, turned about its centre, is what Bounds is the box of.
  Core.Geometry.RotatedRectangle computes that box, the four turned corners,
  and the inverse the hit test asks, and snaps an angle to a multiple of 45.
  Core never measures text: the window measures and writes the layout size in.
• The archive. CurrentVersion is 7, and a board asks for it only when it
  holds a label — frames alone are still 6, and neither is still 5. The check is
  a one-line NeedsVersion7 that the shapes and connector pull requests extend.
  Everything a label is written with is optional in the file and normalized on
  read: an uninstalled font becomes Segoe UI, an angle of 50° becomes 45°, and a
  size outside what a label can be read at is brought back into range.
• Settings. A curated font list and nine sizes in Core.Settings.LabelStyles,
  and AppSettings.Label remembering what the last label was written with. Like
  the pen's color and size it is last-used rather than configured, so it has no
  row in Preferences, and the settings version stays 19.
• The board. Labels are drawn by BoardSurface in z-order with everything
  else, so they show in an export, a preview, the Explorer thumbnail, and the VS
  Code preview. A selected label is outlined along its turned rectangle rather
  than by the box around it; the corner handle stays on the box, which is where
  the gesture looks for it, and dragging it scales the font.
• The Insert tab. A new tab between View and Help (Alt+I), with Text as
  the last button of its row. The shapes pull request is building the same tab in
  parallel with eight buttons in front of Text; whichever merges second keeps one
  tab and both sets of buttons. The optional toolbar Insert flyout and the two
  Toolbar preferences belong to that pull request, and this branch does not
  touch the floating toolbar at all.
• The property bar gains a Font row for a selection of labels: the fonts, the
  sizes, B / I / U, and ↶ ↷ stepping the angle by 45°. Its "applies when" tests
  are now small named statics (HasPrimaryColor, HasThickness, IsLabel) that
  the next pull requests extend by a line each, and the existing Color row now
  reaches a label's text. A pen tap on a combo box opens its list and a tap on a
  button clicks it, as it already did for a toggle.
• Export. The overlay picture that carries the ink now carries the labels
  too, in the editable deck and in the vector PDF path, so nothing vanishes from
  either. Native rotated text is pull request 6. BoardPartitioner names an area
  after a label's first line when a label is the thing it is about.
• One fix on the way past. A command row that stays open — Edit, and now
  Insert — offered its access keys to every plain letter, so typing a word with a
  T in it while a label was open picked the Text tool and committed the label
  half-written. Text being typed now answers the keyboard first, for the label
  editor and for the text container alike.

Decisions the plan did not settle

• AfterInsert is not wired. The preference belongs to the shapes pull
  request and is not on main yet, so the Text tool is sticky: it stays for the
  next click, and Escape puts it down. When the two branches meet, the
  coordinator has one place to hook it — the end of CommitLabelEdit.
• A size read from a file is clamped to 12–96, as the plan says. A label
  scaled past 96 by the corner handle therefore comes back smaller than it was
  saved; the layout is scaled by the same factor so the text still fills its box.
  If a board should keep a 200-pixel heading instead, the clamp in
  LabelStyles.ClampFontSize is the one line to widen.
• Growing text keeps the layout's top-left corner, unrotated, which is what
  PowerPoint does, so a label written at an angle grows along its own baseline.
• The font row applies live while a label is being typed, rather than on
  commit: the change goes into the label and into the editor at once, and the
  whole edit is still one step in the history.
• The Insert row is sticky, like Edit and Help: picking a tool is the start
  of drawing with it, and the row is where the next one is picked from.
• Escape clears a selection before it puts the tool down, so with a label
  selected the first Escape deselects and the second returns to Select.
• The Text glyph is drawn by hand on the same 24-unit grid as the Fluent
  icons around it: Fluent has no plain T at this weight.

To try by hand

Driven with a pen, and with the mouse under both Mouse drawing settings:

• Insert → Text, then click on the canvas: the caret appears where you clicked,
  and what you type stays where you started it as it grows.
• Ctrl+Enter commits; a click anywhere else commits and starts the next label,
  because the tool stays. Escape cancels — a new label leaves nothing behind,
  and an edited one comes back as it was. An empty label disappears.
• F2 on a selected label reopens it; a double-click still centres and fits it.
• ↶ and ↷ in the property bar at 45° and 90°: the outline follows the turn, the
  label stays where it was, and the editor is turned with it when you reopen it.
• Change the font, the size, and B / I / U with a label selected and again while
  one is being typed; then insert the next label and check it is written the
  same way, including after a restart.
• Drag a label by its middle and by its edge; drag the corner handle to scale
  the text; select several labels with a rubber band and recolor them at once.
• Draw ink across a label, move the label, and check the ink moves with it;
  delete the label and check the ink goes too.
• Ctrl+Z through all of it, and Ctrl+C on a single label to paste its text.
• Save, reopen, and export a board with a turned label to a deck and to a PDF:
  the label is in both, in the overlay picture.

With the mouse, in the running application, I inserted a label from the Insert
row, typed it, committed it, turned it 45°, changed its size from the property
bar, dragged it across the board, and undid all of it back to an unmodified
board. The rest of the list above — the pen, the finger, Escape, F2, several
labels at once, linked ink, the clipboard, and a saved and exported board — is
for the morning.

One to watch while you do: choosing a font or a size from the property bar
while the Text tool is still active. Automating that click left a stray empty
label behind once, which a hand could not reproduce and which leaves nothing in
the board either way, but it is worth a look.

🤖 Generated with Claude Code