feat: use the shared mtk tab bar for charmap's top tabs

Replace charmap's bespoke tab drawing/hit-testing with mtk::draw_tab_bar /
mtk::hit_tab_bar so the top tabs match the canonical MontaukOS style used by
the Desktop Settings panel: a surface-colored bar with a bottom border, the
active tab cut out in window_bg with a 3px accent underline, active label in
accent and inactive labels in text_subtle. Tab height is now 36 (theme.tab_h).
Drops the custom hover tint (the canonical style has none).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

programs/src/charmap/main.cpp

@@ -26,6 +26,7 @@
 #include <gui/standalone.hpp>
 #include <gui/truetype.hpp>
 #include <gui/mtk/theme.hpp>
+#include <gui/mtk/widgets.hpp>
 
 extern "C" {
 #include <stdio.h>
@@ -198,7 +199,7 @@ static constexpr int SET_COUNT = (int)(sizeof(SETS) / sizeof(SETS[0]));
 
 static constexpr int INIT_W    = 680;
 static constexpr int INIT_H    = 448;
-static constexpr int TAB_H     = 40;
+static constexpr int TAB_H     = 36;   // matches mtk theme.tab_h / Settings TAB_BAR_H
 static constexpr int FOOTER_H  = 84;
 static constexpr int GRID_PAD  = 12;
 static constexpr int CELL_GAP  = 6;
@@ -219,7 +220,6 @@ static constexpr uint64_t TOAST_MS = 1400;
 static int   g_set = 0;         // active character set index
 static int   g_sel = 0;         // selected glyph index within active set
 static int   g_hover = -1;      // hovered glyph index, or -1
-static int   g_tab_hover = -1;  // hovered tab index, or -1
 static bool  g_copy_hover = false;
 static bool  g_copy_pressed = false;
 static int   g_scroll = 0;      // vertical scroll offset in px
@@ -227,6 +227,7 @@ static uint64_t g_toast_until = 0;
 static char  g_toast[48] = {};
 
 static mtk::Theme g_theme;
+static const char* g_tab_labels[SET_COUNT] = {};  // populated from SETS in _start
 
 // ==== Derived layout ====
 
@@ -293,15 +294,6 @@ static int hit_tile(const Layout& L, int mx, int my) {
     return -1;
 }
 
-static int hit_tab(const Layout& L, int mx, int my) {
-    if (my < L.tabs.y || my >= L.tabs.y + L.tabs.h) return -1;
-    int tab_w = L.tabs.w / SET_COUNT;
-    if (tab_w <= 0) return -1;
-    int idx = mx / tab_w;
-    if (idx < 0 || idx >= SET_COUNT) return -1;
-    return idx;
-}
-
 static void clamp_scroll(const Layout& L) {
     if (g_scroll > L.max_scroll) g_scroll = L.max_scroll;
     if (g_scroll < 0) g_scroll = 0;
@@ -399,27 +391,10 @@ static void render(Canvas& c) {
                             (SCROLLBAR_W - 4) / 2, g_theme.border);
     }
 
-    // ---- Tab bar (opaque) ----
+    // ---- Tab bar (opaque) — canonical MontaukOS top-tab style, matching the
-    c.fill_rect(L.tabs.x, L.tabs.y, L.tabs.w, L.tabs.h, g_theme.window_bg);
+    // Desktop Settings panel (surface bar, window_bg active tab, accent
-    int tab_w = L.tabs.w / SET_COUNT;
+    // underline). Covers any grid spill above the grid top. ----
-    for (int t = 0; t < SET_COUNT; t++) {
+    mtk::draw_tab_bar(c, L.tabs, g_tab_labels, SET_COUNT, g_set, g_theme);
-        int tx = t * tab_w;
-        bool active = (t == g_set);
-        if (t == g_tab_hover && !active)
-            c.fill_rect(tx, L.tabs.y, tab_w, L.tabs.h, g_theme.surface_hover);
-        Color tc = active ? g_theme.accent
-                          : (t == g_tab_hover ? g_theme.text : g_theme.text_muted);
-        int lw = text_width(fonts::system_font, SETS[t].label, TAB_SIZE);
-        int lh = text_height(fonts::system_font, TAB_SIZE);
-        draw_text(c, fonts::system_font, tx + (tab_w - lw) / 2,
-                  L.tabs.y + (L.tabs.h - lh) / 2 - 1, SETS[t].label, tc, TAB_SIZE);
-        if (active) {
-            int uw = lw + 16;
-            c.fill_rounded_rect(tx + (tab_w - uw) / 2, L.tabs.y + L.tabs.h - 3,
-                                uw, 3, 1, g_theme.accent);
-        }
-    }
-    c.fill_rect(L.tabs.x, L.tabs.y + L.tabs.h - 1, L.tabs.w, 1, g_theme.border);
 
     // Bold font for the footer name and Copy button.
     TrueTypeFont* title_font =
@@ -492,8 +467,7 @@ static bool handle_mouse(const montauk::abi::WinEvent& ev, int w, int h) {
     int tile = hit_tile(L, mx, my);
     if (tile != g_hover) { g_hover = tile; redraw = true; }
 
-    int tab = hit_tab(L, mx, my);
+    int tab = mtk::hit_tab_bar(L.tabs, SET_COUNT, mx, my);
-    if (tab != g_tab_hover) { g_tab_hover = tab; redraw = true; }
 
     bool copy_hov = L.copy_btn.contains(mx, my);
     if (copy_hov != g_copy_hover) { g_copy_hover = copy_hov; redraw = true; }
@@ -564,6 +538,7 @@ static bool handle_key(const montauk::abi::KeyEvent& key, int w, int h) {
 extern "C" void _start() {
     fonts::init();
     g_theme = mtk::make_theme();
+    for (int i = 0; i < SET_COUNT; i++) g_tab_labels[i] = SETS[i].label;
 
     WsWindow win;
     if (!win.create("Character Map", INIT_W, INIT_H))
@@ -598,7 +573,6 @@ extern "C" void _start() {
         if (ev.type == 3) break;                 // close
         if (ev.type == 2 || ev.type == 4) {      // resize / scale
             g_hover = -1;
-            g_tab_hover = -1;
             redraw = true;
         } else if (ev.type == 1) {
             redraw = handle_mouse(ev, win.width, win.height);