Commands for focus, scrolling and the clipboard, and pictures from bytes

focus, scroll-to-end, scroll-to-start and scroll-into-view find their
control by the key of its view, and run once the update's controls are
laid out. copy-text puts text on the clipboard, and paste-text sends what
it holds. A command that sends no message ends its fiber when its work is
done, so none is left waiting until the app stops.

image-data shows a picture from the bytes of a file, read again only when
it is given another array.

start-headless! now adds the Fluent theme, as run-app does, so controls
are templated and laid out as in a window.

🤖 Generated with [ECA](https://eca.dev) (anthropic/claude-opus-4-8)

Co-Authored-By: eca-agent <git@eca.dev>

tests/commands.bjo

@@ -0,0 +1,125 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+;; bjogui/tests/commands.bjo — commands that act on the controls and the
+;; clipboard, and pictures from memory.
+;;
+;;     bjo run tests/commands.bjo
+;;
+;; Avalonia runs with no screen, and the app is shown in a window of it, so
+;; that a control can take the keyboard, a scroll view is laid out, and there
+;; is a clipboard.
+
+(import (std prelude))
+(import (std simpletest))
+(import (std interop))
+(import (bjogui view))
+(import (bjogui app))
+
+(import/class
+  (Object        (: System.Object))
+  (Control       (: Avalonia.Controls.Control))
+  (Window        (: Avalonia.Controls.Window (-> Window)))
+  (ContentControl (: Avalonia.Controls.ContentControl))
+  (Layoutable    (: Avalonia.Layout.Layoutable))
+  (InputElement  (: Avalonia.Input.InputElement))
+  (ScrollViewer  (: Avalonia.Controls.ScrollViewer))
+  (Image         (: Avalonia.Controls.Image))
+  (IImage        (: Avalonia.Media.IImage))
+  (Vector        (: Avalonia.Vector)))
+
+(import/extern
+  (content!      (: Avalonia.Controls.ContentControl.Content (-> ContentControl Object void) #:set))
+  (show!         (: Avalonia.Controls.Window.Show (-> Window void)))
+  (width!        (: Avalonia.Layout.Layoutable.Width (-> Layoutable double void) #:set))
+  (height!       (: Avalonia.Layout.Layoutable.Height (-> Layoutable double void) #:set))
+  (update-layout! (: Avalonia.Layout.Layoutable.UpdateLayout (-> Layoutable void)))
+  (focused?      (: Avalonia.Input.InputElement.IsFocused (-> InputElement bool) #:get))
+  (offset-of     (: Avalonia.Controls.ScrollViewer.Offset (-> ScrollViewer Vector) #:get))
+  (vector-y      (: Avalonia.Vector.Y (-> Vector double) #:get))
+  (source-of     (: Avalonia.Controls.Image.Source (-> Image IImage) #:get))
+  (sleep-ms      (: System.Threading.Thread.Sleep (-> int void) #:blocking)))
+
+(type (: Msg (Union FocusName FocusOther End Start Into (: Copy string) Paste (: Pasted (Option string)))))
+(type (: Model (Record (: messages int) (: pasted (Option string)))))
+
+(: (-> Msg Model (Tuple Model (List (Event Msg)))))
+(defun (gui-update msg m0)
+  (def m (record-set m0 (messages (+ (.messages m0) 1))))
+  (match msg
+    (FocusName (next m (focus "name")))
+    (FocusOther (next m (focus "other")))
+    (End (next m (scroll-to-end "log")))
+    (Start (next m (scroll-to-start "log")))
+    (Into (next m (scroll-into-view "line 25")))
+    ((Copy s) (next m (copy-text s)))
+    (Paste (next m (paste-text Pasted)))
+    ((Pasted s) (next (record-set m (pasted s))))))
+
+(def picture (file-read-bytes "docs/mixer.png"))
+
+(: (-> Model (View Msg)))
+(defun (view m)
+  (column
+    (keyed "name" (text-input "" (fun (s) Start)))                                    ; 0
+    (keyed "other" (text-input "" (fun (s) Start)))                                   ; 1
+    (keyed "log" (scroll (apply column (vec->array (vec-map (fun (i) (keyed #"line ${i}" (text #"line ${i}")))
+                                                            (->vec (range 0 40)))))
+                         #:height 60.0))                                              ; 2
+    (image-data picture #:width 46.0 #:height 30.0)                                   ; 3
+    (image-data (: (make-array 3 #:fill (cast byte 7)) (Array byte)))))               ; 4
+
+(defun (main)
+  (start-headless!)
+  (def w (Window.))
+  (width! (cast Layoutable w) 300.0)
+  (height! (cast Layoutable w) 400.0)
+  (def app (start-app (Model (messages 0) (pasted None)) gui-update view
+                      (fun (c) (content! (cast ContentControl w) (cast Object c)))))
+  (show! w)
+  (defun (ctl path) (app-control-at app path))
+  (defun (settle) (app-run-pending! app) (update-layout! (cast Layoutable w)))
+  (: (-> (-> bool) bool))
+  (defun (wait-for done?)
+    (let go ((tries 0))
+      (settle)
+      (cond ((done?) #t)
+            ((> tries 200) #f)
+            (else (sleep-ms 10) (go (+ tries 1))))))
+  (defun (log-offset) (vector-y (offset-of (cast ScrollViewer (ctl '(2))))))
+  (settle)
+
+  ;; --- focus ------------------------------------------------------------------------
+  (app-dispatch! app FocusName)
+  (expect "focus gives the keyboard to the keyed control"
+          (wait-for (fun () (focused? (cast InputElement (ctl '(0)))))) #t)
+  (app-dispatch! app FocusOther)
+  (expect "and to another" (wait-for (fun () (focused? (cast InputElement (ctl '(1)))))) #t)
+  (expect "which the first has no more" (focused? (cast InputElement (ctl '(0)))) #f)
+
+  ;; --- scrolling --------------------------------------------------------------------
+  (expect "the log starts at the top" (log-offset) 0.0)
+  (app-dispatch! app End)
+  (expect "scroll-to-end" (wait-for (fun () (> (log-offset) 500.0))) #t)
+  (app-dispatch! app Start)
+  (expect "scroll-to-start" (wait-for (fun () (= (log-offset) 0.0))) #t)
+  (app-dispatch! app Into)
+  (expect "scroll-into-view" (wait-for (fun () (> (log-offset) 300.0))) #t)
+
+  ;; --- the clipboard -----------------------------------------------------------------
+  (app-dispatch! app (Copy "copied"))
+  (app-dispatch! app Paste)
+  (expect "a copy is pasted" (wait-for (fun () (= (.pasted (app-model app)) (Some "copied")))) #t)
+
+  ;; --- commands that send nothing --------------------------------------------------
+  (sleep-ms 50)
+  (settle)
+  (expect "send nothing: only the messages dispatched, and Pasted" (.messages (app-model app)) 8)
+
+  ;; --- pictures from memory ---------------------------------------------------------
+  (expect "a picture from bytes" (eq? (cast Object (source-of (cast Image (ctl '(3))))) (clr-default)) #f)
+  (expect "bytes that are no picture show nothing"
+          (eq? (cast Object (source-of (cast Image (ctl '(4))))) (clr-default)) #t)
+
+  (println "bjogui commands ok"))