fix(partition-view): Use Ctrl-click or ⌘-click (instead of middle-click)

This new key-binding is macOS-compliant (tested with both Firefox and Safari).

Co-Authored-By: Yann Regis-Gianas <[email protected]>
Co-Authored-By: Érik Martin-Dorel <[email protected]>

Author: yurug

docs/howto-classify-students-answers.md

@@ -21,7 +21,7 @@ Follow these steps:
 
 1. Go to the teaching tab in the LearnOCaml Web UI (needs a teacher token).
 
-2. Middle-click on the exercise `x` in the list of exercises.
+2. Hold Ctrl (on macOS: Hold ⌘) and left click on the exercise `x` in the list of exercises.
 
 3. Enter `foo` in the dialog box.
 

src/app/learnocaml_teacher_tab.ml

@@ -236,7 +236,13 @@ let rec teacher_tab token _select _params () =
               H.a_ondblclick (fun _ -> open_exercise_ ());
               H.a_onmouseup (fun ev ->
                   Js.Optdef.case ev##.which (fun () -> true) @@ fun btn ->
-                  if btn = Dom_html.Middle_button then open_partition_ () else true);
+                  if (Js.to_bool ev##.ctrlKey ||
+                      Js.to_bool ev##.metaKey (* ⌘ on macOS *))
+                     && btn = Dom_html.Left_button
+                  then
+                    open_partition_ ()
+                  else
+                    true);
             ] [
               auto_checkbox_td ();
               H.td ~a:[indent_style group_level]