feat: add scrolling with configurable scrolloff

src/IO/UI.py

@@ -12,6 +12,8 @@ if TYPE_CHECKING:
 class UI:
     def __init__(self, app: App):
         self._app = app
+        self._scroll_top = 0
+        self._scroll_path = None
 
     HEADER_ROWS = 1
 
@@ -31,14 +33,38 @@ class UI:
 
         items = navigator.items
         available = max(0, height - self.HEADER_ROWS)
-        for index in range(min(available, len(items))):
-            item = items[index]
-            self._render_item(stdscr, item, index, index + self.HEADER_ROWS, width)
+        top = self._update_scroll(navigator, available)
+        for offset, item in enumerate(items[top:top + available]):
+            index = top + offset
+            self._render_item(stdscr, item, index, offset + self.HEADER_ROWS, width)
 
         prompt = self.app.prompt
         if prompt:
             self._render_modal(stdscr, prompt, height, width)
 
+    def _update_scroll(self, navigator, available: int) -> int:
+        current_path = navigator.history[-1]
+        if current_path != self._scroll_path:
+            self._scroll_path = current_path
+            self._scroll_top = 0
+
+        total = len(navigator.items)
+        if available <= 0 or total <= available:
+            self._scroll_top = 0
+            return self._scroll_top
+
+        offset = min(self.app.config.scroll_offset, (available - 1) // 2)
+        pos = navigator.cursor.pos
+        max_top = total - available
+
+        if pos < self._scroll_top + offset:
+            self._scroll_top = pos - offset
+        elif pos > self._scroll_top + available - 1 - offset:
+            self._scroll_top = pos - available + 1 + offset
+
+        self._scroll_top = max(0, min(self._scroll_top, max_top))
+        return self._scroll_top
+
     MODAL_MAX_WIDTH = 60
     MODAL_PADDING = 2
 

src/core/Config.py

@@ -20,15 +20,17 @@ DEFAULT_KEYBINDS: dict[str, list[str]] = {
 }
 
 DEFAULT_CURSOR_RESET = "top"
+DEFAULT_SCROLL_OFFSET = 4
 
 
 class Config:
     def __init__(self, keybinds: dict[str, list[str]], cursor_reset: str,
-                 sort_mode: str, theme: Theme) -> None:
+                 sort_mode: str, theme: Theme, scroll_offset: int) -> None:
         self._keybinds = keybinds
         self._cursor_reset = cursor_reset
         self._sort_mode = sort_mode
         self._theme = theme
+        self._scroll_offset = scroll_offset
         self._key_to_action: dict[str, str] = {
             key: action
             for action, keys in keybinds.items()
@@ -57,7 +59,13 @@ class Config:
                   f"falling back to {Sort.DEFAULT_MODE!r}", file=sys.stderr)
             sort_mode = Sort.DEFAULT_MODE
         theme = Theme.load(data)
-        return cls(keybinds, cursor_reset, sort_mode, theme)
+        scroll_offset = data.get("scroll", {}).get("offset",
+                                                     DEFAULT_SCROLL_OFFSET)
+        if not isinstance(scroll_offset, int) or scroll_offset < 0:
+            print(f"pyexplorer: invalid scroll offset {scroll_offset!r}, "
+                  f"falling back to {DEFAULT_SCROLL_OFFSET}", file=sys.stderr)
+            scroll_offset = DEFAULT_SCROLL_OFFSET
+        return cls(keybinds, cursor_reset, sort_mode, theme, scroll_offset)
 
     @staticmethod
     def _default_path() -> Path:
@@ -81,3 +89,7 @@ class Config:
     @property
     def theme(self) -> Theme:
         return self._theme
+
+    @property
+    def scroll_offset(self) -> int:
+        return self._scroll_offset