feat: auto hide tabs widget if there are less than {n} tabs

This can be configured via an integer argument in the bar widget descriptor, or
via the tab styles configuration file. A value of 0 will effectively disable
auto hide.

src/tui/WidgetList.zig

@@ -24,12 +24,14 @@ parent: Plane,
 allocator: Allocator,
 widgets: ArrayList(WidgetState),
 layout_: Layout,
+layout_empty: bool = true,
 direction: Direction,
 box: ?Widget.Box = null,
 ctx: ?*anyopaque = null,
 on_render: *const fn (ctx: ?*anyopaque, theme: *const Widget.Theme) void = on_render_default,
 after_render: *const fn (ctx: ?*anyopaque, theme: *const Widget.Theme) void = on_render_default,
 on_resize: *const fn (ctx: ?*anyopaque, self: *Self, pos_: Widget.Box) void = on_resize_default,
+on_layout: *const fn (ctx: ?*anyopaque, self: *Self) Widget.Layout = on_layout_default,
 
 pub fn createH(allocator: Allocator, parent: Plane, name: [:0]const u8, layout_: Layout) error{OutOfMemory}!*Self {
     const self = try allocator.create(Self);
@@ -71,7 +73,7 @@ pub fn widget(self: *Self) Widget {
 }
 
 pub fn layout(self: *Self) Widget.Layout {
-    return self.layout_;
+    return self.on_layout(self.ctx, self);
 }
 
 pub fn deinit(self: *Self, allocator: std.mem.Allocator) void {
@@ -214,6 +216,10 @@ fn on_resize_default(_: ?*anyopaque, self: *Self, pos: Widget.Box) void {
     self.resize(pos);
 }
 
+fn on_layout_default(_: ?*anyopaque, self: *Self) Widget.Layout {
+    return self.layout_;
+}
+
 pub fn resize(self: *Self, pos_: Widget.Box) void {
     self.box = pos_;
     var pos = pos_;
@@ -235,6 +241,7 @@ pub fn resize(self: *Self, pos_: Widget.Box) void {
             },
         }
     }
+    self.layout_empty = avail == total and dynamics == 0;
 
     const dyn_size = avail / if (dynamics > 0) dynamics else 1;
     const rounded: usize = if (dyn_size * dynamics < avail) avail - dyn_size * dynamics else 0;

src/tui/status/bar.zig

@@ -12,6 +12,7 @@ pub fn create(allocator: std.mem.Allocator, parent: Plane, config: []const u8, s
     var w = try WidgetList.createH(allocator, parent, "statusbar", .{ .static = 1 });
     if (style == .grip) w.after_render = render_grip;
     w.ctx = w;
+    w.on_layout = on_layout;
     var it = std.mem.splitScalar(u8, config, ' ');
     while (it.next()) |widget_name| {
         try w.add(status_widget.create(widget_name, allocator, w.plane, event_handler) catch |e| switch (e) {
@@ -22,6 +23,13 @@ pub fn create(allocator: std.mem.Allocator, parent: Plane, config: []const u8, s
     return w.widget();
 }
 
+fn on_layout(_: ?*anyopaque, w: *WidgetList) Widget.Layout {
+    return if (w.layout_empty)
+        .{ .static = 0 }
+    else
+        .{ .static = 1 };
+}
+
 fn render_grip(ctx: ?*anyopaque, theme: *const Widget.Theme) void {
     const w: *WidgetList = @ptrCast(@alignCast(ctx.?));
     if (w.hover()) {

src/tui/status/tabs.zig

@@ -11,7 +11,11 @@ const Widget = @import("../Widget.zig");
 const WidgetList = @import("../WidgetList.zig");
 const Button = @import("../Button.zig");
 
+const default_min_tabs = 2;
+
 const @"style.config" = struct {
+    default_minimum_tabs_shown: usize = 2,
+
     dirty_indicator: []const u8 = " ",
 
     spacer: []const u8 = "|",
@@ -52,10 +56,11 @@ const @"style.config" = struct {
 };
 pub const Style = @"style.config";
 
-pub fn create(allocator: std.mem.Allocator, parent: Plane, event_handler: ?EventHandler, _: ?[]const u8) @import("widget.zig").CreateError!Widget {
+pub fn create(allocator: std.mem.Allocator, parent: Plane, event_handler: ?EventHandler, arg: ?[]const u8) @import("widget.zig").CreateError!Widget {
+    const min_tabs = if (arg) |str_size| std.fmt.parseInt(usize, str_size, 10) catch null else null;
     const self = try allocator.create(TabBar);
     errdefer allocator.destroy(self);
-    self.* = try TabBar.init(allocator, parent, event_handler);
+    self.* = try TabBar.init(allocator, parent, event_handler, min_tabs);
     return Widget.to(self);
 }
 
@@ -67,6 +72,7 @@ const TabBar = struct {
     event_handler: ?EventHandler,
     tabs: []TabBarTab = &[_]TabBarTab{},
     active_buffer_ref: ?usize = null,
+    minimum_tabs_shown: usize,
 
     tab_style: Style,
     tab_style_bufs: [][]const u8,
@@ -78,7 +84,7 @@ const TabBar = struct {
         widget: Widget,
     };
 
-    fn init(allocator: std.mem.Allocator, parent: Plane, event_handler: ?EventHandler) !Self {
+    fn init(allocator: std.mem.Allocator, parent: Plane, event_handler: ?EventHandler, min_tabs: ?usize) !Self {
         var w = try WidgetList.createH(allocator, parent, "tabs", .dynamic);
         w.ctx = w;
         const tab_style, const tab_style_bufs = root.read_config(Style, allocator);
@@ -90,6 +96,7 @@ const TabBar = struct {
             .event_handler = event_handler,
             .tab_style = tab_style,
             .tab_style_bufs = tab_style_bufs,
+            .minimum_tabs_shown = min_tabs orelse tab_style.default_minimum_tabs_shown,
         };
     }
 
@@ -101,7 +108,10 @@ const TabBar = struct {
     }
 
     pub fn layout(self: *Self) Widget.Layout {
-        return self.widget_list_widget.layout();
+        return if (self.tabs.len >= self.minimum_tabs_shown)
+            self.widget_list_widget.layout()
+        else
+            .{ .static = 0 };
     }
 
     pub fn update(self: *Self) void {