- Added dark mode mode constants, config storage as an integer, and a helper to resolve Auto/Dark/Light using system preferences where available.

- Replaced the dark mode checkbox with an Auto/Dark/Light color mode selector and ensured palette edits use the resolved mode.
- Applied the resolved color mode consistently across palette saving and GTK styling in the user list and channel tree/theme application paths.

src/common/cfgfiles.c

@@ -437,7 +437,7 @@ const struct prefs vars[] =
 	{"gui_tab_dialogs", P_OFFINT (hex_gui_tab_dialogs), TYPE_BOOL},
 	{"gui_tab_dots", P_OFFINT (hex_gui_tab_dots), TYPE_BOOL},
 	{"gui_tab_icons", P_OFFINT (hex_gui_tab_icons), TYPE_BOOL},
-	{"gui_dark_mode", P_OFFINT (hex_gui_dark_mode), TYPE_BOOL},
+	{"gui_dark_mode", P_OFFINT (hex_gui_dark_mode), TYPE_INT},
 	{"gui_tab_layout", P_OFFINT (hex_gui_tab_layout), TYPE_INT},
 	{"gui_tab_middleclose", P_OFFINT (hex_gui_tab_middleclose), TYPE_BOOL},
 	{"gui_tab_newtofront", P_OFFINT (hex_gui_tab_newtofront), TYPE_INT},

src/common/zoitechat.h

@@ -83,6 +83,10 @@ gboolean zoitechat_import_theme (const char *path, GError **error);
 #define USERNAMELEN 10
 #define HIDDEN_CHAR	8			/* invisible character for xtext */
 
+#define ZOITECHAT_DARK_MODE_AUTO 0
+#define ZOITECHAT_DARK_MODE_DARK 1
+#define ZOITECHAT_DARK_MODE_LIGHT 2
+
 struct nbexec
 {
 	int myfd;

src/fe-gtk/chanview.c

@@ -122,7 +122,7 @@ chanview_apply_theme (chanview *cv)
 		return;
 
 	w = GTK_WIDGET (tv->tree);
-	if (prefs.hex_gui_dark_mode)
+	if (fe_dark_mode_is_enabled ())
 	{
 		gtk_widget_modify_base (w, GTK_STATE_NORMAL, &colors[COL_BG]);
 		gtk_widget_modify_text (w, GTK_STATE_NORMAL, &colors[COL_FG]);

src/fe-gtk/fe-gtk.c

@@ -270,6 +270,59 @@ static const char adwaita_workaround_rc[] =
 	"}"
 	"widget \"*.zoitechat-inputbox\" style \"zoitechat-input-workaround\"";
 
+static gboolean
+fe_system_prefers_dark (void)
+{
+	GtkSettings *settings = gtk_settings_get_default ();
+	gboolean prefer_dark = FALSE;
+	char *theme_name = NULL;
+
+	if (!settings)
+		return FALSE;
+
+	if (g_object_class_find_property (G_OBJECT_GET_CLASS (settings),
+	                                  "gtk-application-prefer-dark-theme"))
+	{
+		g_object_get (settings, "gtk-application-prefer-dark-theme", &prefer_dark, NULL);
+	}
+
+	if (!prefer_dark)
+	{
+		g_object_get (settings, "gtk-theme-name", &theme_name, NULL);
+		if (theme_name)
+		{
+			char *lower = g_ascii_strdown (theme_name, -1);
+			if (g_str_has_suffix (lower, "-dark") || g_strrstr (lower, "dark"))
+				prefer_dark = TRUE;
+			g_free (lower);
+			g_free (theme_name);
+		}
+	}
+
+	return prefer_dark;
+}
+
+gboolean
+fe_dark_mode_is_enabled_for (unsigned int mode)
+{
+	switch (mode)
+	{
+	case ZOITECHAT_DARK_MODE_DARK:
+		return TRUE;
+	case ZOITECHAT_DARK_MODE_LIGHT:
+		return FALSE;
+	case ZOITECHAT_DARK_MODE_AUTO:
+	default:
+		return fe_system_prefers_dark ();
+	}
+}
+
+gboolean
+fe_dark_mode_is_enabled (void)
+{
+	return fe_dark_mode_is_enabled_for (prefs.hex_gui_dark_mode);
+}
+
 GtkStyle *
 create_input_style (GtkStyle *style)
 {
@@ -317,7 +370,7 @@ void
 fe_init (void)
 {
 	palette_load ();
-	palette_apply_dark_mode (prefs.hex_gui_dark_mode);
+	palette_apply_dark_mode (fe_dark_mode_is_enabled ());
 	key_init ();
 	pixmaps_init ();
 

src/fe-gtk/fe-gtk.h

@@ -182,6 +182,9 @@ typedef struct session_gui
 extern cairo_surface_t *channelwin_pix;
 extern cairo_surface_t *dialogwin_pix;
 
+gboolean fe_dark_mode_is_enabled (void);
+gboolean fe_dark_mode_is_enabled_for (unsigned int mode);
+
 #define SPELL_ENTRY_GET_TEXT(e) ((char *)(gtk_entry_get_text (GTK_ENTRY(e))))
 #define SPELL_ENTRY_SET_TEXT(e,txt) gtk_entry_set_text(GTK_ENTRY(e),txt)
 #define SPELL_ENTRY_SET_EDITABLE(e,v) gtk_editable_set_editable(GTK_EDITABLE(e),v)

src/fe-gtk/maingui.c

@@ -2650,7 +2650,7 @@ mg_create_userlist (session_gui *gui, GtkWidget *box)
          * - When "Dark mode" is enabled, we also force the user list to use the
          *   palette colors so it doesn't stay blindingly white on GTK2 themes.
          */
-        if (prefs.hex_gui_ulist_style || prefs.hex_gui_dark_mode)
+        if (prefs.hex_gui_ulist_style || fe_dark_mode_is_enabled ())
         {
                 gtk_widget_modify_base (ulist, GTK_STATE_NORMAL, &colors[COL_BG]);
                 gtk_widget_modify_text (ulist, GTK_STATE_NORMAL, &colors[COL_FG]);

src/fe-gtk/palette.c

@@ -311,20 +311,21 @@ palette_save (void)
 	char prefname[256];
 	const GdkColor *lightpal = colors;
 	const GdkColor *darkpal = NULL;
+	gboolean dark_mode_active = fe_dark_mode_is_enabled ();
 
 	/* If we're currently in dark mode, keep colors.conf's legacy keys as the user's light palette. */
-	if (prefs.hex_gui_dark_mode && user_colors_valid)
+	if (dark_mode_active && user_colors_valid)
 		lightpal = user_colors;
 
 	/* If we're currently in light mode, ensure the snapshot stays in sync. */
-	if (!prefs.hex_gui_dark_mode)
+	if (!dark_mode_active)
 	{
 		memcpy (user_colors, colors, sizeof (user_colors));
 		user_colors_valid = TRUE;
 	}
 
 	/* If dark mode is enabled but we haven't snapshotted a custom dark palette yet, capture it now. */
-	if (prefs.hex_gui_dark_mode && !dark_user_colors_valid)
+	if (dark_mode_active && !dark_user_colors_valid)
 	{
 		memcpy (dark_user_colors, colors, sizeof (dark_user_colors));
 		dark_user_colors_valid = TRUE;
@@ -332,7 +333,7 @@ palette_save (void)
 
 	if (dark_user_colors_valid)
 		darkpal = dark_user_colors;
-	else if (prefs.hex_gui_dark_mode)
+	else if (dark_mode_active)
 		darkpal = colors; /* current dark palette (likely defaults) */
 
 	fh = zoitechat_open_file ("colors.conf", O_TRUNC | O_WRONLY | O_CREAT, 0600, XOF_DOMODE);