feat: add scroll bar to Time Zone countries list

programs/src/timezone/main.cpp

@@ -54,6 +54,8 @@ static int g_saved_country = 0;
 static int g_saved_zone = 0;
 static int g_country_scroll = 0;
 static int g_zone_scroll = 0;
+static bool g_country_sb_dragging = false;
+static int  g_country_sb_drag_offset = 0;
 static int g_focus_pane = 0; // 0=country list, 1=zone list
 static int g_mouse_x = -1;
 static int g_mouse_y = -1;
@@ -517,14 +519,43 @@ static void draw_list_frame(Canvas& canvas, const Rect& list, const mtk::Theme&
     canvas.rect(list.x, list.y, list.w, list.h, theme.border);
 }
 
+static int country_content_extent() {
+    return g_country_count * ROW_H;
+}
+
+static int country_view_extent(const Rect& list) {
+    return visible_rows(list) * ROW_H;
+}
+
+static bool country_scrollbar_visible(const Rect& list) {
+    return mtk::scrollbar_needed(country_content_extent(), country_view_extent(list));
+}
+
+static Rect country_scrollbar_track(const Rect& list) {
+    if (!country_scrollbar_visible(list)) return {0, 0, 0, 0};
+    Rect inner = {list.x + 1, list.y + 2, list.w - 2, list.h - 4};
+    return mtk::scrollbar_track_rect(inner);
+}
+
+static Rect country_scrollbar_thumb(const Rect& list) {
+    Rect track = country_scrollbar_track(list);
+    if (track.empty()) return {0, 0, 0, 0};
+    return mtk::scrollbar_thumb_rect(track,
+                                     country_content_extent(),
+                                     country_view_extent(list),
+                                     g_country_scroll * ROW_H);
+}
+
 static void draw_country_list(Canvas& canvas, const Rect& list, const mtk::Theme& theme) {
     draw_list_frame(canvas, list, theme);
+    bool sb_visible = country_scrollbar_visible(list);
+    int item_w = list.w - 4 - (sb_visible ? mtk::SCROLLBAR_W : 0);
     int rows = visible_rows(list);
     for (int row = 0; row < rows; row++) {
         int index = g_country_scroll + row;
         if (index >= g_country_count) break;
 
-        Rect item = {list.x + 2, list.y + 2 + row * ROW_H, list.w - 4, ROW_H - 2};
+        Rect item = {list.x + 2, list.y + 2 + row * ROW_H, item_w, ROW_H - 2};
         bool selected = index == g_selected_country;
         mtk::draw_list_row(canvas, item, selected, (index & 1) != 0, theme);
 
@@ -533,6 +564,14 @@ static void draw_country_list(Canvas& canvas, const Rect& list, const mtk::Theme
         canvas.text(item.x + 8, item.y + (item.h - system_font_height()) / 2,
                     label, selected ? theme.accent_fg : theme.text);
     }
+
+    if (sb_visible) {
+        Rect track = country_scrollbar_track(list);
+        Rect thumb = country_scrollbar_thumb(list);
+        bool hovered = track.contains(g_mouse_x, g_mouse_y) || g_country_sb_dragging;
+        mtk::draw_scrollbar(canvas, track, thumb, hovered,
+                            g_country_sb_dragging, theme);
+    }
 }
 
 static void draw_zone_list(Canvas& canvas, const Rect& list, const mtk::Theme& theme) {
@@ -680,9 +719,49 @@ static bool handle_mouse(const Montauk::WinEvent& ev) {
         }
     }
 
+    // Country scrollbar drag
+    Rect csb_track = country_scrollbar_track(country);
+    Rect csb_thumb = country_scrollbar_thumb(country);
+    bool left_held = (ev.mouse.buttons & 1) != 0;
+    bool just_released = !(ev.mouse.buttons & 1) && (ev.mouse.prev_buttons & 1);
+
+    if (g_country_sb_dragging) {
+        if (left_held && !csb_track.empty()) {
+            int thumb_top = g_mouse_y - g_country_sb_drag_offset;
+            int px_offset = mtk::scrollbar_offset_from_thumb_top(
+                csb_track, country_content_extent(),
+                country_view_extent(country), csb_thumb.h, thumb_top);
+            int new_scroll = px_offset / ROW_H;
+            if (new_scroll != g_country_scroll) {
+                g_country_scroll = new_scroll;
+                clamp_scrolls();
+                redraw = true;
+            }
+            return redraw;
+        }
+        if (just_released) {
+            g_country_sb_dragging = false;
+            return true;
+        }
+    }
+
     bool clicked = (ev.mouse.buttons & 1) && !(ev.mouse.prev_buttons & 1);
     if (!clicked) return redraw;
 
+    if (!csb_track.empty() && csb_track.contains(g_mouse_x, g_mouse_y)) {
+        if (csb_thumb.contains(g_mouse_x, g_mouse_y)) {
+            g_country_sb_dragging = true;
+            g_country_sb_drag_offset = g_mouse_y - csb_thumb.y;
+        } else {
+            int rows = visible_rows(country);
+            int delta = rows > 1 ? rows - 1 : 1;
+            if (g_mouse_y < csb_thumb.y) g_country_scroll -= delta;
+            else                          g_country_scroll += delta;
+            clamp_scrolls();
+        }
+        return true;
+    }
+
     if (country.contains(g_mouse_x, g_mouse_y)) {
         int row = (g_mouse_y - country.y - 2) / ROW_H;
         int index = g_country_scroll + row;