Editor2

crates/editor2/src/scroll/scroll_amount.rs

@@ -0,0 +1,28 @@
+use crate::Editor;
+use serde::Deserialize;
+
+#[derive(Clone, PartialEq, Deserialize)]
+pub enum ScrollAmount {
+    // Scroll N lines (positive is towards the end of the document)
+    Line(f32),
+    // Scroll N pages (positive is towards the end of the document)
+    Page(f32),
+}
+
+impl ScrollAmount {
+    pub fn lines(&self, editor: &mut Editor) -> f32 {
+        match self {
+            Self::Line(count) => *count,
+            Self::Page(count) => editor
+                .visible_line_count()
+                .map(|mut l| {
+                    // for full pages subtract one to leave an anchor line
+                    if count.abs() == 1.0 {
+                        l -= 1.0
+                    }
+                    (l * count).trunc()
+                })
+                .unwrap_or(0.),
+        }
+    }
+}