added errors.nim module for UI error handling

karax/errors.nim

@@ -0,0 +1,30 @@
+## Error handling logic for form input validation.
+
+import karax, jdict
+
+var
+  gerrorMsgs = newJDict[cstring, cstring]()
+  gerrorCounter = 0
+
+proc hasErrors*(): bool = gerrorCounter != 0
+
+proc disableOnError*(): cstring = toDisabled(hasErrors())
+
+proc getError*(field: cstring): cstring =
+  if not gerrorMsgs.contains(field):
+    result = ""
+  else:
+    result = gerrorMsgs[field]
+
+proc setError*(field, msg: cstring) =
+  let previous = getError(field)
+  if len(msg) == 0:
+    if len(previous) != 0: dec(gerrorCounter)
+  else:
+    if len(previous) == 0: inc(gerrorCounter)
+  gerrorMsgs[field] = msg
+
+proc clearErrors*() =
+  let m = gerrorMsgs
+  for k in m.keys:
+    setError(k, "")