Replace scrollbar state with simple offset struct

Introduce Offset type to track scroll positions and replace
ScrollbarState fields in SkirmishState
Update keybindings, App::draw, Widget impl, and BoardWidget::new
to use mutable references and the new Offset struct.
Adjust imports accordingly.

src/app/app.rs

@@ -52,7 +52,7 @@ impl App {
         Ok(())
     }
 
-    fn draw(&self, frame: &mut Frame<'_>) {
+    fn draw(&mut self, frame: &mut Frame<'_>) {
         frame.render_widget(self, frame.area());
     }
 

src/app/keybindings/skirmish.rs

@@ -7,10 +7,10 @@ use ratatui::crossterm::event::KeyEvent;
 pub fn skirmish_keybindings(app: &mut App, key_event: &KeyEvent) {
     if let Some(action) = event_to_action(&key_event) {
         match action {
-            Action::ScrollUp => app.states.skirmish.vertical_scrollbar.prev(),
+            Action::ScrollUp => app.states.skirmish.vertical_offset.prev(),
-            Action::ScrollDown => app.states.skirmish.vertical_scrollbar.next(),
+            Action::ScrollDown => app.states.skirmish.vertical_offset.next(),
-            Action::ScrollLeft => app.states.skirmish.horizontal_scrollbar.prev(),
+            Action::ScrollLeft => app.states.skirmish.horizontal_offset.prev(),
-            Action::ScrollRight => app.states.skirmish.horizontal_scrollbar.next(),
+            Action::ScrollRight => app.states.skirmish.horizontal_offset.next(),
             Action::Quit => app.exit = true,
             Action::Quit2 => app.exit = true,
             Action::Esc => app.view = View::MainMenu,

src/app/state.rs

@@ -1,7 +1,7 @@
-use ratatui::widgets::ScrollbarState;
-
 use crate::{
-    app::states::{MainMenuState, PerkDecksState, SettingsState, SkillsConfigState, SkirmishState},
+    app::states::{
+        MainMenuState, Offset, PerkDecksState, SettingsState, SkillsConfigState, SkirmishState,
+    },
     cli::Cli,
 };
 
@@ -25,8 +25,8 @@ impl GameStates {
             skirmish: SkirmishState {
                 id: 1,
                 name: "Skirmish",
-                vertical_scrollbar: ScrollbarState::new(0),
+                vertical_offset: Offset::new(),
-                horizontal_scrollbar: ScrollbarState::new(0),
+                horizontal_offset: Offset::new(),
             },
             perk_decks: PerkDecksState {
                 id: 2,

src/app/states/mod.rs

@@ -8,4 +8,4 @@ pub use main_menu::MainMenuState;
 pub use perk_decks::{PerkDecks, PerkDecksState};
 pub use settings::SettingsState;
 pub use skills_config::SkillsConfigState;
-pub use skirmish::{GameMode, SkirmishState};
+pub use skirmish::{GameMode, Offset, SkirmishState};

src/app/states/skirmish.rs

@@ -1,12 +1,39 @@
 use clap::ValueEnum;
-use ratatui::widgets::ScrollbarState;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Offset {
+    value: usize,
+    max: usize,
+}
+
+impl Offset {
+    pub fn new() -> Self {
+        Self { value: 0, max: 0 }
+    }
+
+    pub fn get_value(&self) -> usize {
+        self.value
+    }
+
+    pub fn set_max(&mut self, max: usize) {
+        self.max = max;
+    }
+
+    pub fn next(&mut self) {
+        self.value = self.value.saturating_add(1).min(self.max);
+    }
+
+    pub fn prev(&mut self) {
+        self.value = self.value.saturating_sub(1).max(0)
+    }
+}
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct SkirmishState {
     pub id: usize,
     pub name: &'static str,
-    pub vertical_scrollbar: ScrollbarState,
+    pub vertical_offset: Offset,
-    pub horizontal_scrollbar: ScrollbarState,
+    pub horizontal_offset: Offset,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, ValueEnum)]

src/app/view.rs

@@ -13,7 +13,7 @@ pub enum View {
     SkillsConfig,
 }
 
-impl Widget for &App {
+impl Widget for &mut App {
     fn render(self, area: Rect, buf: &mut Buffer)
     where
         Self: Sized,

src/app/views/skirmish.rs

@@ -11,7 +11,7 @@ use ratatui::{
     widgets::{Block, Borders, Padding, Paragraph, Widget},
 };
 
-pub fn skirmish_view(app: &App, area: Rect, buf: &mut Buffer) {
+pub fn skirmish_view(app: &mut App, area: Rect, buf: &mut Buffer) {
     let vertical_layout: Layout = Layout::vertical([
         Constraint::Length(4),
         Constraint::Fill(1),
@@ -70,7 +70,7 @@ pub fn skirmish_view(app: &App, area: Rect, buf: &mut Buffer) {
         board_block.render(main_area, buf);
 
         let cells_area: Rect = board_area.inner(Margin {
-            horizontal: 1,
+            horizontal: 3,
             vertical: 1,
         });
 

src/app/widgets/board.rs

@@ -16,35 +16,35 @@ pub struct BoardWidget {
 }
 
 impl BoardWidget {
-    pub fn new(app: &App, area_width: u16, area_height: u16) -> Self {
+    pub fn new(app: &mut App, area_width: u16, area_height: u16) -> Self {
-        let cell_width: u16 = 7;
+        const CELL_HIGHT: u16 = 4;
-        let cell_height: u16 = 4;
+        const CELL_WIDTH: u16 = 7;
 
-        let cols: u16 = area_width / cell_width;
+        let rows: u16 = area_height / CELL_HIGHT;
-        let rows: u16 = area_height / cell_height;
+        let cols: u16 = area_width / CELL_WIDTH;
 
-        let h_max_offset: u16 = if app.states.settings.map_height as u16 > rows {
+        let h_max_offset: usize = if app.states.settings.map_height as u16 > rows {
             app.states.settings.map_height as u16 - rows
         } else {
             0
-        };
+        } as usize;
 
-        let v_max_offset: u16 = if app.states.settings.map_width as u16 > cols {
+        let v_max_offset: usize = if app.states.settings.map_width as u16 > cols {
             app.states.settings.map_width as u16 - cols
         } else {
             0
-        };
+        } as usize;
 
-        // let h_offset: usize = (cell_height * rows as u16 / area_height) as usize;
+        app.states.skirmish.horizontal_offset.set_max(h_max_offset);
-        // let v_offset: usize = (cell_width * cols as u16 / area_width) as usize;
+        app.states.skirmish.vertical_offset.set_max(v_max_offset);
 
         Self {
-            cell_width,
+            cell_width: CELL_WIDTH,
-            cell_height,
+            cell_height: CELL_HIGHT,
             cols,
             rows,
-            h_offset: h_max_offset as usize,
+            h_offset: app.states.skirmish.horizontal_offset.get_value(),
-            v_offset: v_max_offset as usize,
+            v_offset: app.states.skirmish.vertical_offset.get_value(),
         }
     }
 }