feat: make tabs draggable

src/renderer/vaxis/Layer.zig

@@ -0,0 +1,117 @@
+const std = @import("std");
+const vaxis = @import("vaxis");
+
+pub const Plane = @import("Plane.zig");
+
+const Layer = @This();
+
+view: View,
+y_off: i32 = 0,
+x_off: i32 = 0,
+plane_: Plane,
+
+const View = struct {
+    allocator: std.mem.Allocator,
+    screen: vaxis.Screen,
+    unicode: *const vaxis.Unicode,
+
+    pub const Config = struct {
+        h: u16,
+        w: u16,
+    };
+
+    pub fn init(allocator: std.mem.Allocator, unicode: *const vaxis.Unicode, config: Config) std.mem.Allocator.Error!View {
+        return .{
+            .allocator = allocator,
+            .screen = try vaxis.Screen.init(allocator, .{
+                .rows = config.h,
+                .cols = config.w,
+                .x_pixel = 0,
+                .y_pixel = 0,
+            }),
+            .unicode = unicode,
+        };
+    }
+
+    pub fn deinit(self: *View) void {
+        self.screen.deinit(self.allocator);
+    }
+};
+
+pub const Options = struct {
+    y: i32 = 0,
+    x: i32 = 0,
+    h: u16 = 0,
+    w: u16 = 0,
+};
+
+pub fn init(allocator: std.mem.Allocator, unicode: *const vaxis.Unicode, opts: Options) std.mem.Allocator.Error!*Layer {
+    const self = try allocator.create(Layer);
+    self.* = .{
+        .view = try View.init(allocator, unicode, .{
+            .h = opts.h,
+            .w = opts.w,
+        }),
+        .y_off = opts.y,
+        .x_off = opts.x,
+        .plane_ = undefined,
+    };
+    const name = "layer";
+    self.plane_ = .{
+        .window = self.window(),
+        .name_buf = undefined,
+        .name_len = name.len,
+    };
+    @memcpy(self.plane_.name_buf[0..name.len], name);
+    return self;
+}
+
+pub fn deinit(self: *Layer) void {
+    const allocator = self.view.allocator;
+    self.view.deinit();
+    allocator.destroy(self);
+}
+
+fn window(self: *Layer) vaxis.Window {
+    return .{
+        .x_off = 0,
+        .y_off = 0,
+        .parent_x_off = 0,
+        .parent_y_off = 0,
+        .width = self.view.screen.width,
+        .height = self.view.screen.height,
+        .screen = &self.view.screen,
+        .unicode = self.view.unicode,
+    };
+}
+
+pub fn plane(self: *Layer) *Plane {
+    return &self.plane_;
+}
+
+pub fn draw(self: *const Layer, plane_: Plane) void {
+    if (self.x_off >= plane_.window.width) return;
+    if (self.y_off >= plane_.window.height) return;
+
+    const src_y = 0;
+    const src_x = 0;
+    const src_h: usize = self.view.screen.height;
+    const src_w = self.view.screen.width;
+
+    const dst_dim_y: i32 = @intCast(plane_.dim_y());
+    const dst_dim_x: i32 = @intCast(plane_.dim_x());
+    const dst_y = self.y_off;
+    const dst_x = self.x_off;
+    const dst_w = @min(src_w, dst_dim_x - dst_x);
+
+    for (src_y..src_h) |src_row_| {
+        const src_row: i32 = @intCast(src_row_);
+        const src_row_offset = src_row * src_w;
+        const dst_row_offset = (dst_y + src_row) * plane_.window.screen.width;
+        if (dst_y + src_row > dst_dim_y) return;
+        @memcpy(
+            plane_.window.screen.buf[@intCast(dst_row_offset + dst_x)..@intCast(dst_row_offset + dst_x + dst_w)],
+            self.view.screen.buf[@intCast(src_row_offset + src_x)..@intCast(src_row_offset + dst_w)],
+        );
+    }
+}

src/renderer/vaxis/renderer.zig

@@ -9,6 +9,7 @@ const builtin = @import("builtin");
 const RGB = @import("color").RGB;
 
 pub const Plane = @import("Plane.zig");
+pub const Layer = @import("Layer.zig");
 pub const Cell = @import("Cell.zig");
 pub const CursorShape = vaxis.Cell.CursorShape;
 

src/tui/Box.zig

@@ -1,4 +1,5 @@
 const Plane = @import("renderer").Plane;
+const Layer = @import("renderer").Layer;
 
 const Self = @This();
 
@@ -35,6 +36,15 @@ pub fn from(n: Plane) Self {
     };
 }
 
+pub fn to_layer(self: Self) Layer.Options {
+    return .{
+        .y = @intCast(self.y),
+        .x = @intCast(self.x),
+        .h = @intCast(self.h),
+        .w = @intCast(self.w),
+    };
+}
+
 pub fn is_abs_coord_inside(self: Self, y: usize, x: usize) bool {
     return y >= self.y and y < self.y + self.h and x >= self.x and x < self.x + self.w;
 }

src/tui/Button.zig

@@ -77,6 +77,8 @@ fn State(ctx_type: type) type {
         plane: Plane,
         active: bool = false,
         hover: bool = false,
+        drag_anchor: ?Widget.Pos = null,
+        drag_pos: ?Widget.Pos = null,
         opts: Options(ctx_type),
 
         const Self = @This();
@@ -120,6 +122,7 @@ fn State(ctx_type: type) type {
                 switch (btn_enum) {
                     input.mouse.BUTTON1 => {
                         self.active = true;
+                        self.drag_anchor = self.to_rel_cursor(x, y);
                         tui.need_render();
                     },
                     input.mouse.BUTTON4, input.mouse.BUTTON5 => {
@@ -131,9 +134,12 @@ fn State(ctx_type: type) type {
                 return true;
             } else if (try m.match(.{ "B", input.event.release, tp.extract(&btn), tp.any, tp.extract(&x), tp.extract(&y), tp.any, tp.any })) {
                 self.call_click_handler(@enumFromInt(btn), self.to_rel_cursor(x, y));
+                self.drag_anchor = null;
+                self.drag_pos = null;
                 tui.need_render();
                 return true;
-            } else if (try m.match(.{ "D", input.event.press, tp.extract(&btn), tp.more })) {
+            } else if (try m.match(.{ "D", input.event.press, tp.extract(&btn), tp.any, tp.extract(&x), tp.extract(&y), tp.any, tp.any })) {
+                self.drag_pos = .{ .x = x, .y = y };
                 if (self.opts.on_event) |h| {
                     self.active = false;
                     h.send(from, m) catch {};
@@ -145,6 +151,8 @@ fn State(ctx_type: type) type {
                     h.send(from, m) catch {};
                 }
                 self.call_click_handler(@enumFromInt(btn), self.to_rel_cursor(x, y));
+                self.drag_anchor = null;
+                self.drag_pos = null;
                 tui.need_render();
                 return true;
             } else if (try m.match(.{ "H", tp.extract(&self.hover) })) {
@@ -152,6 +160,8 @@ fn State(ctx_type: type) type {
                 tui.need_render();
                 return true;
             }
+            self.drag_anchor = null;
+            self.drag_pos = null;
             return self.opts.on_receive(&self.opts.ctx, self, from, m);
         }
 

src/tui/status/tabs.zig

@@ -6,6 +6,7 @@ const root = @import("soft_root").root;
 const EventHandler = @import("EventHandler");
 const Plane = @import("renderer").Plane;
 const Buffer = @import("Buffer");
+const input = @import("input");
 
 const tui = @import("../tui.zig");
 const Widget = @import("../Widget.zig");
@@ -187,6 +188,30 @@ pub const TabBar = struct {
         return false;
     }
 
+    fn handle_event(self: *Self, from: tp.pid_ref, m: tp.message) tp.result {
+        if (self.event_handler) |event_handler| try event_handler.send(from, m);
+        if (try m.match(.{ "D", input.event.press, @intFromEnum(input.mouse.BUTTON1), tp.more })) {
+            const dragging = for (self.tabs, 0..) |*tab, idx| {
+                if (tab.widget.dynamic_cast(Tab.ButtonType)) |btn|
+                    if (btn.drag_pos) |_| break idx;
+            } else return;
+            const hover_ = for (self.tabs, 0..) |*tab, idx| {
+                if (tab.widget.dynamic_cast(Tab.ButtonType)) |btn|
+                    if (btn.hover) break idx;
+            } else return;
+            if (dragging != hover_) {
+                const tmp = self.tabs[dragging];
+                self.tabs[dragging] = self.tabs[hover_];
+                self.tabs[hover_] = tmp;
+                if (self.tabs[dragging].widget.dynamic_cast(Tab.ButtonType)) |btn| btn.hover = false;
+                self.update();
+                for (self.widget_list.widgets.items) |*widgetstate| if (widgetstate.widget.dynamic_cast(Tab.ButtonType)) |btn| if (btn.drag_pos) |_|
+                    tui.set_drag_source(&widgetstate.widget);
+                tui.refresh_hover();
+            }
+        }
+    }
+
     pub fn handle_resize(self: *Self, pos: Widget.Box) void {
         self.widget_list_widget.resize(pos);
         self.plane = self.widget_list.plane;
@@ -258,7 +283,7 @@ pub const TabBar = struct {
     fn place_new_tab(self: *Self, result: *std.ArrayListUnmanaged(TabBarTab), buffer: *Buffer) !void {
         const buffer_manager = tui.get_buffer_manager() orelse @panic("tabs no buffer manager");
         const buffer_ref = buffer_manager.buffer_to_ref(buffer);
-        const tab = try Tab.create(self, buffer_ref, &self.tab_style, self.event_handler);
+        const tab = try Tab.create(self, buffer_ref, &self.tab_style);
         const pos = switch (self.place_next) {
             .atend => try result.addOne(self.allocator),
             .before => |i| if (i < result.items.len)
@@ -395,7 +420,7 @@ pub const TabBar = struct {
             if (buffer_name) |name| if (name_to_ref(name)) |buffer_ref| {
                 (try result.addOne(self.allocator)).* = .{
                     .buffer_ref = buffer_ref,
-                    .widget = try Tab.create(self, buffer_ref, &self.tab_style, self.event_handler),
+                    .widget = try Tab.create(self, buffer_ref, &self.tab_style),
                 };
             };
         }
@@ -416,6 +441,7 @@ const Tab = struct {
     tab_style: *const Style,
     close_pos: ?c_uint = null,
     save_pos: ?c_uint = null,
+    on_event: ?EventHandler = null,
 
     const Mode = enum { active, inactive, selected };
 
@@ -425,7 +451,6 @@ const Tab = struct {
         tabbar: *TabBar,
         buffer_ref: usize,
         tab_style: *const Style,
-        event_handler: ?EventHandler,
     ) !Widget {
         const buffer_manager = tui.get_buffer_manager() orelse @panic("tabs no buffer manager");
         const buffer = buffer_manager.buffer_from_ref(buffer_ref);
@@ -436,7 +461,7 @@ const Tab = struct {
             .on_click2 = Tab.on_click2,
             .on_layout = Tab.layout,
             .on_render = Tab.render,
-            .on_event = event_handler,
+            .on_event = EventHandler.bind(tabbar, TabBar.handle_event),
         });
     }
 
@@ -463,159 +488,182 @@ const Tab = struct {
 
     fn render(self: *@This(), btn: *ButtonType, theme: *const Widget.Theme) bool {
         const active = self.tabbar.active_buffer_ref == self.buffer_ref;
+        if (btn.drag_pos) |pos| {
+            self.render_dragging(&btn.plane, theme);
+            const anchor: Widget.Pos = btn.drag_anchor orelse .{};
+            var box = Widget.Box.from(btn.plane);
+            box.y = @intCast(@max(pos.y, anchor.y) - anchor.y);
+            box.x = @intCast(@max(pos.x, anchor.x) - anchor.x);
+            if (tui.top_layer(box.to_layer())) |top_layer| {
+                self.render_selected(top_layer, btn.opts.label, false, theme, active);
+            }
+        } else {
             const mode: Mode = if (btn.hover) .selected else if (active) .active else .inactive;
             switch (mode) {
-            .selected => self.render_selected(btn, theme, active),
+                .selected => self.render_selected(&btn.plane, btn.opts.label, btn.hover, theme, active),
-            .active => self.render_active(btn, theme),
+                .active => self.render_active(&btn.plane, btn.opts.label, btn.hover, theme),
-            .inactive => self.render_inactive(btn, theme),
+                .inactive => self.render_inactive(&btn.plane, btn.opts.label, btn.hover, theme),
+            }
         }
         return false;
     }
 
-    fn render_selected(self: *@This(), btn: *ButtonType, theme: *const Widget.Theme, active: bool) void {
+    fn render_selected(self: *@This(), plane: *Plane, label: []const u8, hover: bool, theme: *const Widget.Theme, active: bool) void {
-        btn.plane.set_base_style(theme.editor);
+        plane.set_base_style(theme.editor);
-        btn.plane.erase();
+        plane.erase();
-        btn.plane.home();
+        plane.home();
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.inactive_fg.from_theme(theme),
             .bg = self.tab_style.inactive_bg.from_theme(theme),
         });
-        btn.plane.fill(" ");
+        plane.fill(" ");
-        btn.plane.home();
+        plane.home();
         if (active) {
-            btn.plane.set_style(.{
+            plane.set_style(.{
                 .fg = self.tab_style.selected_fg.from_theme(theme),
                 .bg = self.tab_style.selected_bg.from_theme(theme),
             });
-            btn.plane.fill(" ");
+            plane.fill(" ");
-            btn.plane.home();
+            plane.home();
         }
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.selected_left_fg.from_theme(theme),
             .bg = self.tab_style.selected_left_bg.from_theme(theme),
         });
-        _ = btn.plane.putstr(self.tab_style.selected_left) catch {};
+        _ = plane.putstr(self.tab_style.selected_left) catch {};
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.selected_fg.from_theme(theme),
             .bg = self.tab_style.selected_bg.from_theme(theme),
         });
-        self.render_content(btn, self.tab_style.selected_fg.from_theme(theme), theme);
+        self.render_content(plane, label, hover, self.tab_style.selected_fg.from_theme(theme), theme);
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.selected_right_fg.from_theme(theme),
             .bg = self.tab_style.selected_right_bg.from_theme(theme),
         });
-        _ = btn.plane.putstr(self.tab_style.selected_right) catch {};
+        _ = plane.putstr(self.tab_style.selected_right) catch {};
     }
 
-    fn render_active(self: *@This(), btn: *ButtonType, theme: *const Widget.Theme) void {
+    fn render_active(self: *@This(), plane: *Plane, label: []const u8, hover: bool, theme: *const Widget.Theme) void {
-        btn.plane.set_base_style(theme.editor);
+        plane.set_base_style(theme.editor);
-        btn.plane.erase();
+        plane.erase();
-        btn.plane.home();
+        plane.home();
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.inactive_fg.from_theme(theme),
             .bg = self.tab_style.inactive_bg.from_theme(theme),
         });
-        btn.plane.fill(" ");
+        plane.fill(" ");
-        btn.plane.home();
+        plane.home();
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.active_fg.from_theme(theme),
             .bg = self.tab_style.active_bg.from_theme(theme),
         });
-        btn.plane.fill(" ");
+        plane.fill(" ");
-        btn.plane.home();
+        plane.home();
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.active_left_fg.from_theme(theme),
             .bg = self.tab_style.active_left_bg.from_theme(theme),
         });
-        _ = btn.plane.putstr(self.tab_style.active_left) catch {};
+        _ = plane.putstr(self.tab_style.active_left) catch {};
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.active_fg.from_theme(theme),
             .bg = self.tab_style.active_bg.from_theme(theme),
         });
-        self.render_content(btn, self.tab_style.active_fg.from_theme(theme), theme);
+        self.render_content(plane, label, hover, self.tab_style.active_fg.from_theme(theme), theme);
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.active_right_fg.from_theme(theme),
             .bg = self.tab_style.active_right_bg.from_theme(theme),
         });
-        _ = btn.plane.putstr(self.tab_style.active_right) catch {};
+        _ = plane.putstr(self.tab_style.active_right) catch {};
     }
 
-    fn render_inactive(self: *@This(), btn: *ButtonType, theme: *const Widget.Theme) void {
+    fn render_inactive(self: *@This(), plane: *Plane, label: []const u8, hover: bool, theme: *const Widget.Theme) void {
-        btn.plane.set_base_style(theme.editor);
+        plane.set_base_style(theme.editor);
-        btn.plane.erase();
+        plane.erase();
-        btn.plane.home();
+        plane.home();
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.inactive_fg.from_theme(theme),
             .bg = self.tab_style.inactive_bg.from_theme(theme),
         });
-        btn.plane.fill(" ");
+        plane.fill(" ");
-        btn.plane.home();
+        plane.home();
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.inactive_left_fg.from_theme(theme),
             .bg = self.tab_style.inactive_left_bg.from_theme(theme),
         });
-        _ = btn.plane.putstr(self.tab_style.inactive_left) catch {};
+        _ = plane.putstr(self.tab_style.inactive_left) catch {};
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.inactive_fg.from_theme(theme),
             .bg = self.tab_style.inactive_bg.from_theme(theme),
         });
-        self.render_content(btn, self.tab_style.inactive_fg.from_theme(theme), theme);
+        self.render_content(plane, label, hover, self.tab_style.inactive_fg.from_theme(theme), theme);
 
-        btn.plane.set_style(.{
+        plane.set_style(.{
             .fg = self.tab_style.inactive_right_fg.from_theme(theme),
             .bg = self.tab_style.inactive_right_bg.from_theme(theme),
         });
-        _ = btn.plane.putstr(self.tab_style.inactive_right) catch {};
+        _ = plane.putstr(self.tab_style.inactive_right) catch {};
     }
 
-    fn render_content(self: *@This(), btn: *ButtonType, fg: ?Widget.Theme.Color, theme: *const Widget.Theme) void {
+    fn render_dragging(self: *@This(), plane: *Plane, theme: *const Widget.Theme) void {
+        plane.set_base_style(theme.editor);
+        plane.erase();
+        plane.home();
+        plane.set_style(.{
+            .fg = self.tab_style.inactive_fg.from_theme(theme),
+            .bg = self.tab_style.inactive_bg.from_theme(theme),
+        });
+        plane.fill(" ");
+        plane.home();
+    }
+
+    fn render_content(self: *@This(), plane: *Plane, label: []const u8, hover: bool, fg: ?Widget.Theme.Color, theme: *const Widget.Theme) void {
         const buffer_manager = tui.get_buffer_manager() orelse @panic("tabs no buffer manager");
         const buffer_ = buffer_manager.buffer_from_ref(self.buffer_ref);
         const is_dirty = if (buffer_) |buffer| buffer.is_dirty() else false;
-        self.render_padding(&btn.plane, .left);
+        self.render_padding(plane, .left);
         if (self.tab_style.file_type_icon) if (buffer_) |buffer| if (buffer.file_type_icon) |icon| {
             const color_: ?u24 = if (buffer.file_type_color) |color| if (!(color == 0xFFFFFF or color == 0x000000 or color == 0x000001)) color else null else null;
             if (color_) |color|
-                btn.plane.set_style(.{ .fg = .{ .color = color } });
+                plane.set_style(.{ .fg = .{ .color = color } });
-            _ = btn.plane.putstr(icon) catch {};
+            _ = plane.putstr(icon) catch {};
             if (color_) |_|
-                btn.plane.set_style(.{ .fg = fg });
+                plane.set_style(.{ .fg = fg });
-            _ = btn.plane.putstr("  ") catch {};
+            _ = plane.putstr("  ") catch {};
         };
-        _ = btn.plane.putstr(btn.opts.label) catch {};
+        _ = plane.putstr(label) catch {};
-        _ = btn.plane.putstr(" ") catch {};
+        _ = plane.putstr(" ") catch {};
         self.close_pos = null;
         self.save_pos = null;
-        if (btn.hover) {
+        if (hover) {
             if (is_dirty) {
                 if (self.tab_style.save_icon_fg) |color|
-                    btn.plane.set_style(.{ .fg = color.from_theme(theme) });
+                    plane.set_style(.{ .fg = color.from_theme(theme) });
-                self.save_pos = btn.plane.cursor_x();
+                self.save_pos = plane.cursor_x();
-                _ = btn.plane.putstr(self.tabbar.tab_style.save_icon) catch {};
+                _ = plane.putstr(self.tabbar.tab_style.save_icon) catch {};
             } else {
-                btn.plane.set_style(.{ .fg = self.tab_style.close_icon_fg.from_theme(theme) });
+                plane.set_style(.{ .fg = self.tab_style.close_icon_fg.from_theme(theme) });
-                self.close_pos = btn.plane.cursor_x();
+                self.close_pos = plane.cursor_x();
-                _ = btn.plane.putstr(self.tabbar.tab_style.close_icon) catch {};
+                _ = plane.putstr(self.tabbar.tab_style.close_icon) catch {};
             }
         } else if (is_dirty) {
             if (self.tab_style.dirty_indicator_fg) |color|
-                btn.plane.set_style(.{ .fg = color.from_theme(theme) });
+                plane.set_style(.{ .fg = color.from_theme(theme) });
-            _ = btn.plane.putstr(self.tabbar.tab_style.dirty_indicator) catch {};
+            _ = plane.putstr(self.tabbar.tab_style.dirty_indicator) catch {};
         } else {
             if (self.tab_style.clean_indicator_fg) |color|
-                btn.plane.set_style(.{ .fg = color.from_theme(theme) });
+                plane.set_style(.{ .fg = color.from_theme(theme) });
-            _ = btn.plane.putstr(self.tabbar.tab_style.clean_indicator) catch {};
+            _ = plane.putstr(self.tabbar.tab_style.clean_indicator) catch {};
         }
-        btn.plane.set_style(.{ .fg = fg });
+        plane.set_style(.{ .fg = fg });
-        self.render_padding(&btn.plane, .right);
+        self.render_padding(plane, .right);
     }
 
     fn render_padding(self: *@This(), plane: *Plane, side: enum { left, right }) void {

src/tui/tui.zig

@@ -31,6 +31,7 @@ const Allocator = std.mem.Allocator;
 
 allocator: Allocator,
 rdr_: renderer,
+top_layer_: ?*renderer.Layer = null,
 config_: @import("config"),
 config_bufs: [][]const u8,
 session_tab_width: ?usize = null,
@@ -507,12 +508,25 @@ fn render(self: *Self) void {
         break :ret if (self.mainview_) |mv| mv.render(self.current_theme()) else false;
     };
 
+    if (self.top_layer_) |top_layer_| {
+        const frame = tracy.initZone(@src(), .{ .name = "tui blit top layer" });
+        defer frame.deinit();
+        self.logger.print("top_layer: {}:{}:{}:{}", .{
+            top_layer_.y_off,
+            top_layer_.x_off,
+            top_layer_.view.screen.height,
+            top_layer_.view.screen.width,
+        });
+        top_layer_.draw(self.rdr_.stdplane());
+    }
+
     {
         const frame = tracy.initZone(@src(), .{ .name = renderer.log_name ++ " render" });
         defer frame.deinit();
         self.rdr_.render() catch |e| self.logger.err("render", e);
         tracy.frameMark();
     }
+    self.top_layer_reset();
 
     self.idle_frame_count = if (self.unrendered_input_events_count > 0)
         0
@@ -1395,6 +1409,11 @@ pub fn get_keybind_mode() ?Mode {
     return self.input_mode_ orelse self.delayed_init_input_mode;
 }
 
+pub fn set_drag_source(drag_source: *Widget) void {
+    const self = current();
+    self.drag_source = drag_source;
+}
+
 pub fn reset_drag_context() void {
     const self = current();
     self.drag_source = null;
@@ -1427,6 +1446,24 @@ fn stdplane(self: *Self) renderer.Plane {
     return self.rdr_.stdplane();
 }
 
+pub fn top_layer(opts: renderer.Layer.Options) ?*renderer.Plane {
+    const self = current();
+    if (self.top_layer_) |_| return null;
+    self.top_layer_ = renderer.Layer.init(
+        self.allocator,
+        self.rdr_.stdplane().window.unicode,
+        opts,
+    ) catch @panic("OOM toplayer");
+    return self.top_layer_.?.plane();
+}
+
+fn top_layer_reset(self: *Self) void {
+    if (self.top_layer_) |top_layer_| {
+        top_layer_.deinit();
+        self.top_layer_ = null;
+    }
+}
+
 pub fn egc_chunk_width(chunk: []const u8, abs_col: usize, tab_width: usize) usize {
     return plane().egc_chunk_width(chunk, abs_col, tab_width);
 }