Canvas · Graphs and boards: node graph, flow chart, mind map, whiteboard

NodeGraph joins Nodes by wires between typed Ports: a title drags a
node, a drag out of an output lands on an input of the same kind, an
input takes one wire, and a press on a wired input lifts its wire.
Links join shapes on the plane and follow them, straight or at right
angles, with an arrow and words; the Connector tool draws them and the
Note tool drops a sticky note. A double press with Select writes on a
shape. FlowChart draws Steps as ellipses, boxes and diamonds with their
words. MindMap lays topics out from a root, half to each side, and asks
the owner to add, remove and rename by key. Whiteboard keeps its own
tool, view and selection over a board it hands back after each change.
Painting moves to canvas::paint; a press on the tool layer goes through
canvas::press, and the layer focuses itself and asks to delete.

src/canvas/writing.rs

@@ -0,0 +1,54 @@
+use std::rc::Rc;
+
+use gpui::{
+    AnyElement, App, Entity, InteractiveElement, IntoElement, MouseButton, ParentElement, Pixels,
+    SharedString, Styled, Window, div,
+};
+
+use super::{gesture::OnPair, view::Frame};
+use crate::forms::{Editing, Input};
+
+/// Opens a field on the words of what `key` names. Enter or leaving hands them to the owner; Escape drops them.
+pub(super) fn begin(
+    editing: &Entity<Editing>,
+    key: SharedString,
+    words: String,
+    on_text: Option<OnPair>,
+    window: &mut Window,
+    cx: &mut App,
+) {
+    log::info!("canvas: writing on {key}");
+    editing.update(cx, |editing, _| {
+        editing.on_commit = Some(Rc::new(
+            move |text: &SharedString, window: &mut Window, cx: &mut App| {
+                log::info!("canvas: {key} reads {text:?}");
+                if let Some(on_text) = &on_text {
+                    on_text(&key, text, window, cx);
+                }
+            },
+        ));
+    });
+    Editing::begin(editing, words, window, cx);
+}
+
+/// The open field over `frame`, in view pixels.
+pub(super) fn field(editing: &Entity<Editing>, frame: Frame, cx: &App) -> Option<AnyElement> {
+    let field = editing.read(cx).field()?;
+    let closing = editing.clone();
+    Some(
+        div()
+            .absolute()
+            .left(Pixels::from(frame.x))
+            .top(Pixels::from(frame.y))
+            .w(Pixels::from(frame.w))
+            .on_mouse_down(MouseButton::Left, |_, _, cx| cx.stop_propagation())
+            .on_key_down(move |event, window, cx| {
+                if event.keystroke.key == "escape" {
+                    cx.stop_propagation();
+                    closing.update(cx, |editing, cx| editing.finish(true, window, cx));
+                }
+            })
+            .child(Input::new(&field))
+            .into_any_element(),
+    )
+}