editor: typewriter centering keys on view and line heights; a placement resets the editor's centering too

src/editor/state.rs

@@ -122,8 +122,8 @@ pub struct CodeEditor {
     /// The text before an input method's composition began, while it runs.
     pub(crate) composing: Option<Snapshot>,
     pub(crate) metrics: Metrics,
-    /// The caret row typewriter scrolling last centered.
-    pub(crate) centered: Option<usize>,
+    /// The caret row, view and line heights last centered.
+    pub(crate) centered: Option<(usize, Pixels, Pixels)>,
     /// Typewriter room rows at each end.
     pub(crate) pad: usize,
     pub(crate) dragging: bool,

src/editor/view.rs

@@ -272,11 +272,11 @@ impl Render for CodeEditor {
         self.metrics.advance = advance;
         self.metrics.line = line;
         // Typewriter: the caret's row centers as it moves.
-        let row = self.primary_row();
-        if self.options.typewriter && self.centered != Some(row) {
+        let centered = (self.primary_row(), self.metrics.height, line);
+        if self.options.typewriter && self.centered != Some(centered) {
             self.scroll
-                .scroll_to_item_strict(row, ScrollStrategy::Center);
-            self.centered = Some(row);
+                .scroll_to_item_strict(centered.0, ScrollStrategy::Center);
+            self.centered = Some(centered);
         }
         let sticky = if self.options.sticky {
             self.sticky(cx)