Will change this commit message to mean something later

examples/modules/active-window-widget.lua

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+-- active-window-widget — shows the focused app right next to the
+-- workspace pills, live-updated via bread.state.watch (no polling, no
+-- bread.on needed).
+--
+-- Demonstrates: WidgetPlacement "right_of_workspaces", a state-watch-driven
+-- widget (as opposed to a timer or event handler), and calling
+-- bread.widget.update from inside the watch callback. breadbar's own bar
+-- doesn't show the focused window anywhere today — this adds that for free.
+--
+-- Drop-in: copy into ~/.config/bread/modules/. Zero configuration.
+
+local M = bread.module({ name = "active-window-widget", version = "1.0.0" })
+
+local function label_for(window)
+    -- A JSON null (no window focused) doesn't necessarily arrive as Lua nil
+    -- through bread.state.* — mlua's serde bridge can hand back a distinct
+    -- null sentinel instead, which `not window` won't catch. Guard on the
+    -- type directly so any non-string value (nil, the sentinel, ...) falls
+    -- through to the placeholder rather than crashing on #window below.
+    if type(window) ~= "string" or window == "" then
+        return "—"
+    end
+    if #window > 24 then
+        return window:sub(1, 24) .. "…"
+    end
+    return window
+end
+
+local function widget_root(window)
+    return { type = "label", text = label_for(window), style = { color = "dim" } }
+end
+
+function M.on_load()
+    bread.widget.register({
+        id = "active-window",
+        placement = "right_of_workspaces",
+        tooltip = "Currently focused window",
+        root = widget_root(bread.state.active_window()),
+    })
+
+    bread.state.watch("active_window", function(new_val)
+        bread.widget.update("active-window", { root = widget_root(new_val) })
+    end)
+end
+
+return M