I wrote a calculator!

!ReadMe

+
+SillyCalc
+=========
+
+This is a silly calculator. Enter expressions in the writeable icon. When
+you press return the result will be displayed in the display icon.
+
+Press escape or close the window to quit the application.
+
+Please be nice to me becuase this is my first desktop application.
+
+It doesn't even deserve an icon.
+
+
+Licence
+-------
+
+You may not distribute this application except as supplied. No cutting it
+up and giving away your bits. No. Really.
+
+
+Note about this release
+-----------------------
+This is an extra special release.
+It has a reporter box that tells you what the error is.
+The application multitasks whilst it's doing it.
+The program doesn't recurse in doing so.
+Once the user has made their response (OK, in this case) the program performs
+some action.
+All this in about half an hour.
+In a program I've not used for a year and a half, in a language that isn't
+even used all that often for Wimp programs.
+
+See 'do_evaluate' for the call to the dialogue box creation. Notice the use
+of a function pointer for the post-user interaction. Ok, so it's actually
+a function object, but JS doesn't really have function pointers so you'll
+just have to live with that.
+Notice that 'dbox_show' includes no heavy trickery.
+Notice that the click handler (case 6 in the Poll loop) triggers the
+function pointer ('dbox_do_this_after') and closes the window.
+
+If you had more dboxes you might duplicate the window on the fly and keep
+track of them through a list. But that's just implementation detail.

!SillyCalc/!Run,feb

+Set SillyCalc$Dir <Obey$Dir>
+Run <SillyCalc$Dir>.JSTest <SillyCalc$Dir>.!RunImage 2> t

!SillyCalc/!RunImage,f81

+
+/* Remap plain print to output to !Console */
+print = print_debug;
+
+Registers.prototype.throwSWI = function(swi)
+          {
+            var err = this.callSWI(swi);
+            if (err)
+              throw(err);
+          };
+
+init_wimp();
+load_templates();
+open_window_front(Main_Window);
+set_caret_end(Main_Window,1)
+Quit = 0;
+while (!Quit)
+{
+  wimp_poll();
+}
+
+/* Load a single template */
+function load_template(name)
+{
+  var R = new Registers;
+
+  /* 1. Read the size of the template */
+  R[1] = 0;
+  R[2] = 0;
+  R[3] = 0;
+  R[4] = 0;
+  R[5] = new Alloc(String(name));
+  R[6] = 0;
+  R.throwSWI("Wimp_LoadTemplate");
+  print("Needs "+R[1]+" for window and icons and "+ R[2]+" for indirect\n");
+
+  /* 2. Allocate space for blocks */
+  var window_data = new Alloc(R[1]);
+  var indirect_data = new Alloc(R[2]);
+
+  /* 3. Load the template */
+  R[1] = window_data;
+  R[2] = indirect_data;
+  R[3] = indirect_data + indirect_data.length;
+  R[4] = -1;
+  R[5] = new Alloc(String(name));
+  R[6] = 0;
+  R.throwSWI("Wimp_LoadTemplate");
+
+  /* 4. Ensure that our indirect data is not released by putting it in
+        a global variable.
+        Note that the window data will be destroyed by garbage collection
+        at some point after we leave this function - it goes out of
+        scope. */
+  IndirectData.push(indirect_data);
+
+  /* 5. Create the window */
+  R[1] = window_data;
+  R.throwSWI("Wimp_CreateWindow");
+
+  /* 6. Return the window handle */
+  return R[0];
+}
+
+/* Load all our templates */
+function load_templates()
+{
+  var R = new Registers;
+
+  /* 0. Initial global object so that we don't lose our indirect data
+        at some later point during garbage collection */
+  IndirectData = new Array;
+
+  /* 1. Open the templates file */
+  R[1] = new Alloc("<SillyCalc$Dir>.Templates");
+  R.throwSWI("Wimp_OpenTemplate");
+
+  /* 2. Load each template */
+  Main_Window = load_template("example");
+  Report_Window = load_template("dbox");
+
+  /* 3. Close the template */
+  R.throwSWI("Wimp_CloseTemplate");
+}
+
+function open_window_front(window)
+{
+  var R = new Registers;
+  var state = new Alloc(36);
+
+  /* Get window state */
+  state.Word[0] = window;
+  R[1] = state;
+  R.throwSWI("Wimp_GetWindowState");
+
+  /* Open at front */
+  state.Word[28] = -1; /* Front */
+  R.throwSWI("Wimp_OpenWindow");
+}
+
+/* Display a message in a dialogue box */
+function dbox_show(message, what_to_do_after)
+{
+  /* Remember what we do after the user responds */
+  dbox_do_this_after = what_to_do_after;
+
+  set_icon_text(Report_Window, 0, message);
+
+  open_window_front(Report_Window);
+}
+
+function init_wimp()
+{
+  var R = new Registers;
+
+  R[0] = 310;
+  R[1] = 0x4b534154;
+  R[2] = new Alloc("JavaScript application");
+  R[3] = message_list = new Alloc(4);
+  message_list.Word[0] = 0;
+
+  err = R.throwSWI("Wimp_Initialise");
+  if (err)
+    throw(err);
+}
+
+function wimp_poll()
+{
+  var poll_block = new Alloc(256);
+  var reason;
+  var err;
+  var R = new Registers;
+
+  R[0] = 1<<24; /* Mask (save FP state) */
+  R[1] = poll_block;
+  err = R.throwSWI("Wimp_Poll");
+  if (err)
+    throw(err);
+
+  reason = R[0];
+  switch (reason)
+  {
+    case 2: /* Open window request */
+      R[1] = poll_block;
+      R.throwSWI("Wimp_OpenWindow");
+      break;
+
+    case 3: /* Close window request */
+      Quit = 1;
+      break;
+
+    case 6: /* Mouse click */
+      var win = poll_block.Word[12];
+      var icon = poll_block.Word[16];
+      if (win == Report_Window)
+      {
+        if (icon == 1)
+        {
+          /* They clicked ok so trigger the operation */
+          dbox_do_this_after(1);
+          /* 1 because we might have some other response later; hell this
+             is only a demo */
+
+          /* And remember to close the dbox too */
+          R[1] = poll_block;
+          poll_block.Word[0] = Report_Window;
+          R.throwSWI("Wimp_CloseWindow");
+        }
+      }
+      break;
+
+    case 8: /* Key press */
+      var key = poll_block.Word[24];
+      print("Key = "+key+"\n");
+      switch (key)
+      {
+        case 13: /* return */
+          do_evaluate();
+          break;
+
+        case 27: /* Escape */
+          Quit=1;
+          break;
+      }
+      break;
+
+    case 17:
+    case 18:
+      var msg = poll_block.Word[16];
+      print("Message "+ hex(msg) + "\n");
+      switch (msg)
+      {
+        case 0:
+          Quit=1;
+          break;
+      }
+      break;
+  }
+}
+
+function get_icon_text(window, icon)
+{
+  var R = new Registers;
+  var gis = new Alloc(8+32);
+  gis.Word[0] = window;
+  gis.Word[4] = icon;
+  R[1] = gis;
+  R.throwSWI("Wimp_GetIconState");
+
+  var flags = gis.Word[8+16];
+  if ((flags & 0x101) != 0x101)
+    return "";
+
+  return Core.StringC[gis.Word[8+20]];
+}
+
+function set_caret_end(window, icon)
+{
+  var R = new Registers;
+  var str = get_icon_text(window, icon);
+
+  R[0] = window;
+  R[1] = icon;
+  R[2] = 0;
+  R[3] = 0;
+  R[4] = -1;
+  R[5] = str.length;
+  R.throwSWI("Wimp_SetCaretPosition");
+}
+
+function set_icon_text(window, icon, string)
+{
+  var R = new Registers;
+  var gis = new Alloc(8+32);
+  gis.Word[0] = window;
+  gis.Word[4] = icon;
+  R[1] = gis;
+  R.throwSWI("Wimp_GetIconState");
+
+  var flags = gis.Word[8+16];
+  if ((flags & 0x101) != 0x101)
+    return;
+
+  string = String(string);
+
+  Core.StringC[gis.Word[8+20]] = string.substr(0, gis.Word[8+28]-1);
+
+  /* Rememer to force an update of the icon */
+  gis.Word[8] = 0;
+  gis.Word[12] = 0;
+  R.throwSWI("Wimp_SetIconState");
+}
+
+function do_evaluate()
+{
+  var str = get_icon_text(Main_Window, 1);
+  var result;
+  try {
+    print("Trying '"+str+"'\n");
+    result = eval(str);
+    print("Got '"+result+"'\n");
+  }
+  catch(err)
+  {
+    print("Failed: "+err+"'\n");
+    dbox_show(err, function(num) { print("User clicked dbox\n"); } );
+    result="ERROR";
+  }
+  set_icon_text(Main_Window, 3, result);
+}
+
+
+function print_debug()
+{
+  var str, i;
+  var R;
+
+  R = new Registers;
+  str = new String("");
+
+  for (i=0; i<arguments.length; i++)
+    str += arguments[i];
+
+  R.throwSWI(0x104); /* OS_WriteI+4 */
+  R[0] = new Alloc(str);
+  R.throwSWI("OS_Write0");
+}