Add connect mode, portals, backlinks and renames (stage 8d, v1)

Part 8d, the last of stage 8, and with it everything on DESIGN.md's v1
list.

Connect mode (C): the cursor goes to another node, a dashed arrow in the
visual color follows it, and Enter links the two; then the cursor goes
back to where C was typed (the user's pick). d removes the line between
them (a branch is cut, and the child comes loose), > puts the node under
the other one, and <Space> a, l, c, s and t style the line as you watch,
making it when it isn't there yet. Everything connect mode changes is one
undo group, and Esc takes it back with History::cancel, which leaves
nothing to redo. From visual mode every selected node connects, and the
line pickers go back to connect mode when they close.

Portals show their document live, from a cache of what each document
file holds (open documents from their buffers, the others from their
files, looked at every second): the root's title, its color and how many
nodes it has, or ? when the document isn't there. Enter or gf goes
through, as a jump, and the pane's breadcrumb starts with the documents
it came through. <Space>p types :portal (the user's pick): a path as :e
takes it, or the title of a new document. Backlinks are put right
whenever a document is opened or saved; the root shows how many, the
Note view lists them, gu goes up to them (the user's pick) and
:backlinks lists them.

File names follow the root's title: when it changed, the next save
renames the file (-2 when the name is taken; a folder's default document
keeps its name), and the portals pointing at it, its backlinks in the
documents it leads to, the recent documents, the capital marks and the
jump lists follow. A portal whose file was moved by hand finds its
document in that folder by uid. Portals in a register keep full paths,
so a pasted portal leads to the same document from any folder.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/mod.rs

@@ -24,14 +24,16 @@ pub mod calls;
 mod clipboard;
 pub mod commands;
 mod configure;
+pub mod connect;
 pub mod documents;
 mod files;
 mod input;
-mod jumps;
+pub mod jumps;
 mod marks;
 pub mod mode;
 pub mod panes;
 pub mod popup;
+pub mod portals;
 pub mod registers;
 mod render;
 mod repeat;
@@ -43,7 +45,7 @@ mod update;
 pub mod visual;
 mod yank;
 
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::time::Instant;
 
 use ratatui::layout::Rect;
@@ -59,6 +61,7 @@ use crate::input::bindings::Context;
 use crate::input::engine::KeyEngine;
 use crate::input::keymap::Keymap;
 use crate::input::mouse::MouseReader;
+use crate::model::DocUid;
 use crate::storage::memory::Memory;
 use crate::ui::theme::Theme;
 use crate::view::canvas::{Camera, CanvasView};
@@ -71,6 +74,7 @@ use documents::{BufferId, Documents};
 use jumps::Jumps;
 use mode::Mode;
 use panes::{PaneId, Panes};
+use portals::Portals;
 use registers::Registers;
 use startup::Opening;
 
@@ -121,18 +125,28 @@ struct Shared {
     mode: Mode,
     theme: Theme,
     view: ViewSettings,
+    /// What the documents portals lead to look like.
+    portals: Portals,
 }
 
 impl Shared {
     /// What a view showing document `buffer` looks at.
     fn ctx(&self, buffer: BufferId) -> ViewContext<'_> {
-        let buffer = &self.docs.get(buffer).buffer;
+        self.ctx_in(buffer, &self.mode)
+    }
+
+    /// What a view showing document `buffer` looks at, in `mode` (the panes
+    /// without the focus are drawn as in normal mode).
+    fn ctx_in<'a>(&'a self, buffer: BufferId, mode: &'a Mode) -> ViewContext<'a> {
+        let open = self.docs.get(buffer);
         ViewContext {
-            doc: buffer.doc(),
-            cursor: buffer.cursor(),
-            mode: &self.mode,
+            doc: open.buffer.doc(),
+            cursor: open.buffer.cursor(),
+            mode,
             theme: &self.theme,
             settings: &self.view,
+            portals: &self.portals,
+            folder: open.file.path.parent().unwrap_or(Path::new(".")),
         }
     }
 
@@ -142,11 +156,23 @@ impl Shared {
     }
 }
 
-/// A pane: one of the documents, through a view, and where it jumped from.
+/// A pane: one of the documents, through a view, where it jumped from, and
+/// the portals it came through.
 struct Pane {
     buffer: BufferId,
     view: Box<dyn View>,
     jumps: Jumps,
+    /// The documents the pane came to this one through, by portals, the
+    /// first one first: the breadcrumb starts with them.
+    trail: Vec<Crumb>,
+}
+
+/// A document a pane came through, by a portal.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Crumb {
+    pub uid: DocUid,
+    /// Its name then.
+    pub title: String,
 }
 
 impl Pane {
@@ -160,14 +186,24 @@ impl Pane {
         if let Some(camera) = camera {
             view.set_camera(camera);
         }
-        Pane { buffer, view, jumps: Jumps::default() }
+        Pane { buffer, view, jumps: Jumps::default(), trail: Vec::new() }
     }
 
     /// The pane shows `buffer` in a new view (a canvas starting at `camera`);
-    /// its jump list stays.
+    /// its jump list and its trail stay.
     fn show(&mut self, buffer: BufferId, kind: ViewKind, camera: Option<Camera>) {
-        let jumps = std::mem::take(&mut self.jumps);
-        *self = Pane { jumps, ..Pane::new(buffer, kind, camera) };
+        let (jumps, trail) = (std::mem::take(&mut self.jumps), std::mem::take(&mut self.trail));
+        *self = Pane { jumps, trail, ..Pane::new(buffer, kind, camera) };
+    }
+
+    /// The pane got to document `uid` another way than a portal: if it came
+    /// through that one, the trail goes back to it; otherwise it starts
+    /// again.
+    fn arrive(&mut self, uid: DocUid) {
+        match self.trail.iter().position(|crumb| crumb.uid == uid) {
+            Some(at) => self.trail.truncate(at),
+            None => self.trail.clear(),
+        }
     }
 }
 
@@ -193,7 +229,7 @@ impl App {
         let first = docs.at(0);
         let mut app = App {
             panes: Panes::new(Pane::new(first, ViewKind::Canvas, None)),
-            shared: Shared { docs, mode: Mode::Normal, theme, view },
+            shared: Shared { docs, mode: Mode::Normal, theme, view, portals: Portals::default() },
             command_history: CommandHistory::from_lines(memory.history.clone()),
             paths,
             settings,
@@ -223,6 +259,10 @@ impl App {
         for loaded in others {
             said.extend(app.add_document(loaded).1);
         }
+        // Once every document named is open, so one that's about to open
+        // isn't written underneath it.
+        app.sync_backlinks(first);
+        app.refresh_portals(true);
         app.message = Message::joined(said);
         app
     }