Added window activation event

Author: dominicletz

lib/desktop/env.ex

@@ -9,6 +9,11 @@ defmodule Desktop.Env do
 
   Also it has a global connect() method to allow binding of :wx event callbacks using
   this long lived process as reference.
+
+  Subscribers (see `subscribe/0`) also receive:
+
+  * `{:desktop, :window_activated, window_id}` — a `Desktop.Window` with registered
+    `id` has become the active frame (user brought the app window to the foreground).
   """
   alias Desktop.Env
   use GenServer
@@ -54,8 +59,15 @@ defmodule Desktop.Env do
       send(pid, e)
     end
 
-    Process.monitor(pid)
-    {:reply, :ok, %Env{d | subs: [pid | subs], events: []}}
+    subs =
+      if pid in subs do
+        subs
+      else
+        Process.monitor(pid)
+        [pid | subs]
+      end
+
+    {:reply, :ok, %Env{d | subs: subs, events: []}}
   end
 
   def handle_call(:wx_env, _from, d = %Env{wx_env: env}) do
@@ -112,6 +124,14 @@ defmodule Desktop.Env do
     {:noreply, %Env{state | windows: [window | windows]}}
   end
 
+  def handle_cast({:notify_subscribers, message}, state = %Env{subs: subs}) do
+    for sub <- subs do
+      send(sub, message)
+    end
+
+    {:noreply, state}
+  end
+
   @impl true
   def handle_info({:reopen_app, []}, state = %Env{windows: windows}) do
     # Handling MacOS event when the app icon is clicked again
@@ -259,11 +279,22 @@ defmodule Desktop.Env do
     * `{:open_file, [filename]}`
     * `{:open_url, [filename]}`
     * `{:new_file, []}`
+    * `{:desktop, :window_activated, window_id}` — from `Desktop.Window` when the
+      frame becomes active (see `Desktop.Env` module doc).
   """
   def subscribe() do
     GenServer.call(__MODULE__, {:subscribe, self()})
   end
 
+  @doc """
+  Delivers a message to all processes that called `subscribe/0`.
+
+  Used internally by `Desktop.Window` for lifecycle events (e.g. frame activation).
+  """
+  def notify_subscribers(message) when is_tuple(message) do
+    GenServer.cast(__MODULE__, {:notify_subscribers, message})
+  end
+
   defp init_sni() do
     # We're protecting the main application from any possible
     # side effects of the SNI startup using a monitored (not linked) process:

lib/desktop/window.ex

@@ -95,6 +95,7 @@ defmodule Desktop.Window do
     :module,
     :taskbar,
     :frame,
+    :id,
     :notifications,
     :webview,
     :home_url,
@@ -158,6 +159,13 @@ defmodule Desktop.Window do
       userData: self()
     )
 
+    unless OS.mobile?() do
+      :wxFrame.connect(frame, :activate,
+        callback: &frame_activate/2,
+        userData: self()
+      )
+    end
+
     if min_size do
       :wxFrame.setMinSize(frame, min_size)
     end
@@ -219,6 +227,7 @@ defmodule Desktop.Window do
 
     ui = %Window{
       frame: frame,
+      id: options[:id],
       webview: Fallback.webview_new(frame),
       notifications: %{},
       home_url: url,
@@ -579,6 +588,23 @@ defmodule Desktop.Window do
     :ok
   end
 
+  def frame_activate(wx(userData: pid), event) do
+    if :wxActivateEvent.getActive(event) do
+      GenServer.cast(pid, :frame_activated)
+    end
+
+    :ok
+  end
+
+  @doc false
+  def handle_cast(:frame_activated, ui = %Window{id: id}) do
+    if id != nil do
+      Desktop.Env.notify_subscribers({:desktop, :window_activated, id})
+    end
+
+    {:noreply, ui}
+  end
+
   @doc false
   def handle_cast(:close_window, ui = %Window{frame: frame, taskbar: taskbar, on_close: on_close}) do
     if on_close == :hide do