Reset horizontal scroll when cursor on empty line

Reset horizontal scroll to 0 when the cursor moves onto an empty/blank line. Adds EditorApp fields (reset_scroll_x_pending, previous_cursor_byte_pos) and initializes them. In ui_editor, pending resets are applied before the ScrollArea so they take effect immediately, cursor movement to an empty line schedules the reset, and the final stored scroll state also respects the reset. Temporarily reduces the UI animation time during editor rendering and restores it afterward.

Author: Avaray

Cargo.lock

@@ -126,6 +126,12 @@ pub struct EditorApp {
     pub(crate) start_maximized: bool,
     /// Current maximized state, updated every frame from the OS viewport
     pub(crate) is_maximized: bool,
+
+    /// Flag to reset horizontal scroll to 0 on next frame (when cursor on empty line)
+    pub(crate) reset_scroll_x_pending: bool,
+
+    /// Previous cursor byte position (to detect navigation)
+    pub(crate) previous_cursor_byte_pos: Option<usize>,
 }
 
 impl EditorApp {
@@ -210,6 +216,8 @@ impl EditorApp {
             last_copy_time: None,
 
             style_dirty: true, // Apply style on startup
+            reset_scroll_x_pending: false,
+            previous_cursor_byte_pos: None,
         }
     }
 }

src/app.rs

@@ -92,6 +92,17 @@ impl EditorApp {
             }
         }
 
+        // Apply pending horizontal scroll reset BEFORE ScrollArea
+        if self.reset_scroll_x_pending {
+            scroll_state.offset.x = 0.0;
+            scroll_state.store(ui.ctx(), scroll_id);
+            self.reset_scroll_x_pending = false;
+        }
+
+        // The user requested the cursor/scroll animation to be 75% faster
+        let original_animation_time = ui.style().animation_time;
+        ui.style_mut().animation_time = original_animation_time * 0.25;
+
         let scroll_output = egui::ScrollArea::both()
             .id_salt("main_editor")
             .auto_shrink(false)
@@ -443,6 +454,20 @@ impl EditorApp {
 
                                 self.highlighted_line = Some(line_num);
 
+                                // Detect if cursor is on an empty or blank line → schedule scroll reset
+                                let line_start = text[..cursor_byte_pos].rfind('\n').map(|i| i + 1).unwrap_or(0);
+                                let line_end = text[cursor_byte_pos..].find('\n').map(|i| cursor_byte_pos + i).unwrap_or(text.len());
+                                let current_line = &text[line_start..line_end];
+                                
+                                // Only reset if the cursor ACTUALLY moved to an empty line
+                                // (don't lock the view to 0 if they try to scroll horizontally while on an empty line)
+                                if self.previous_cursor_byte_pos != Some(cursor_byte_pos) {
+                                    if current_line.trim().is_empty() {
+                                        self.reset_scroll_x_pending = true;
+                                    }
+                                }
+                                self.previous_cursor_byte_pos = Some(cursor_byte_pos);
+
                                 let char_start =
                                     cursor_range.primary.index.min(cursor_range.secondary.index);
                                 let char_end =
@@ -456,8 +481,15 @@ impl EditorApp {
                 });
             });
 
-        // Save final scroll state
-        scroll_output.state.store(ui.ctx(), scroll_id);
+        // Apply horizontal scroll reset for current frame too
+        let mut final_state = scroll_output.state;
+        if self.reset_scroll_x_pending {
+            final_state.offset.x = 0.0;
+        }
+        final_state.store(ui.ctx(), scroll_id);
+
+        // Restore animation time
+        ui.style_mut().animation_time = original_animation_time;
     }
 
     fn handle_tab_key(ui: &egui::Ui, id: egui::Id, unindent: bool, text: &mut String, settings: &crate::settings::Settings, is_modified: &mut bool) {