Reverse order and edit narrative

to highlight potential issues with Distributed and to link to the relevant manual entries

docs/src/manual/async.md

@@ -1,13 +1,16 @@
 # Asynchronous UI
 
 It is possible to perform background computation without interfering with user interface
-responsiveness either using separate processes or using multithreading. Use of a separate
-process includes slightly more overhead but is also more robust.
+responsiveness either using multithreading or using separate processes. Use of a separate
+process includes slightly more overhead but also enusres user interface responsiveness more
+robustly.
 
-Here is an example using a separate process to offload the work.
+Here is an example using [threads](https://docs.julialang.org/en/v1/manual/multi-threading/).
+Notice that this example will freeze the UI during computation unless Julia is run with two
+or more threads (`julia -t2` on the command line).
 
 ```julia
-using Gtk, Distributed
+using Gtk
 
 btn = GtkButton("Start")
 sp = GtkSpinner()
@@ -18,37 +21,39 @@ grid[1,1] = btn
 grid[2,1] = sp
 grid[1:2,2] = ent
 
-id = addprocs(1)[1]
-
 signal_connect(btn, "clicked") do widget
     start(sp)
-    @async begin
+    Threads.@spawn begin
 
-        # Offload work to a separate process and block until it is done.
-        counter = @fetchfrom id begin
-            stop_time = time() + 3
-            counter = 0
-            while time() < stop_time
-                counter += 1
-            end
-            counter
+        # Do work
+        stop_time = time() + 3
+        counter = 0
+        while time() < stop_time
+            counter += 1
         end
 
-        # We are still in the main thread so it is okay to directly access widgets
-        stop(sp)
-        set_gtk_property!(ent, :text, "I counted to $counter in a separate process!")
+        # Interacting with GTK from a thread other than the main thread is
+        # generally not allowed, so we register an idle callback instead.
+        Gtk.GLib.g_idle_add(nothing) do user_data
+            stop(sp)
+            set_gtk_property!(ent, :text, "I counted to $counter in a thread!")
+            Cint(false)
+        end
     end
 end
 
-win = GtkWindow(grid, "Distributed", 200, 200)
+win = GtkWindow(grid, "Threads", 200, 200)
 showall(win)
 ```
 
-And here is an example using threads. Notice that this example will freeze the UI during
-computation unless Julia is run with two or more threads (`julia -t2` on the command line).
+
+Here is an example using a separate process to offload the work. This toy example is
+fairly straightforward, but things can get more complex if the offloaded task is more
+complex. See the [manual](https://docs.julialang.org/en/v1/manual/distributed-computing/) 
+for details.
 
 ```julia
-using Gtk
+using Gtk, Distributed
 
 btn = GtkButton("Start")
 sp = GtkSpinner()
@@ -59,27 +64,29 @@ grid[1,1] = btn
 grid[2,1] = sp
 grid[1:2,2] = ent
 
+id = addprocs(1)[1]
+
 signal_connect(btn, "clicked") do widget
     start(sp)
-    Threads.@spawn begin
+    @async begin
 
-        # Do work
-        stop_time = time() + 3
-        counter = 0
-        while time() < stop_time
-            counter += 1
+        # Offload work to a separate process and block until it is done.
+        counter = @fetchfrom id begin
+            stop_time = time() + 3
+            counter = 0
+            while time() < stop_time
+                counter += 1
+            end
+            counter
         end
 
-        # Interacting with GTK from a thread other than the main thread is
-        # generally not allowed, so we register an idle callback instead.
-        Gtk.GLib.g_idle_add(nothing) do user_data
-            stop(sp)
-            set_gtk_property!(ent, :text, "I counted to $counter in a thread!")
-            Cint(false)
-        end
+        # We are still in the main thread so it is okay to directly access widgets
+        stop(sp)
+        set_gtk_property!(ent, :text, "I counted to $counter in a separate process!")
     end
 end
 
-win = GtkWindow(grid, "Threads", 200, 200)
+win = GtkWindow(grid, "Distributed", 200, 200)
 showall(win)
 ```
+