Rework Scrolling and Zooming

README.md

@@ -29,8 +29,8 @@ reshuffle.
 | Gesture | Result |
 | --- | --- |
 | Double-click empty canvas | New text note, ready to type in |
-| Double-click a note | Edit its Markdown in place |
-| Double-click a file/link node | Open it with the system default application |
+| Double-click a note | Edit its Markdown in an editor window |
+| Double-click a file/link node | Edit a plain-text file, or open anything else with the system default application |
 | Right-click empty canvas | Menu of every node type, added where you clicked |
 | Right-click a node | Colour, bring to front / send to back, delete |
 | Drag a dot on a node's edge | Draw a connection; drop it on empty canvas to create the node too |
@@ -39,8 +39,7 @@ reshuffle.
 | Drag on empty canvas | Rubber-band selection (hold <kbd>Shift</kbd> to add) |
 | Middle- or right-drag | Pan |
 | Drop files on the window | A file node each; a `.canvas` file opens instead |
-| Wheel over a node | Scroll contents that are taller than the node |
-| <kbd>Ctrl</kbd>+wheel | Zoom around the pointer |
+| Wheel | Zoom around the pointer, anywhere on the canvas |
 
 **Markdown in text nodes**: headings, bold/italic/strikethrough, inline and
 fenced code, quotes, bullet, numbered and task lists, rules, images and links.
@@ -125,8 +124,9 @@ The UI toolkit is [egui](https://github.com/emilk/egui) via `eframe`. An
 infinite canvas is essentially one large custom-painted widget, which is what
 immediate-mode GUI is good at, and it builds to a single binary on both targets
 without a GTK or Qt runtime. Pan and zoom are a transform on a dedicated egui
-layer, so real widgets (the in-place Markdown editor, links) keep working while
-the canvas is scaled.
+layer, so real widgets (file previews, links) keep working while the canvas is
+scaled. Cards crop what they cannot show and editing happens in a window of its
+own, so nothing on the canvas is hidden behind a scroll bar.
 
 | Module | Responsibility |
 | --- | --- |