next step to get stateful components

experiments/example.nim

@@ -10,7 +10,6 @@ proc carousel*(key: VKey): VNode {.component.} =
 
   proc next(ev: Event; n: VNode) =
     counter = (counter + 1) mod images.len
-    markDirty key
 
   result = buildHtml(tdiv(key=key)):
     text images[counter]

experiments/oldwidgets.nim

@@ -201,3 +201,51 @@ proc visibleKeys(e: Node; a, b: var VKey; h, count: var int) =
   else:
     for i in 0..<e.len:
       visibleKeys(e[i], a, b, h, count)
+
+template toState(x): untyped = "state" & x
+proc accessState(sv: string): NimNode {.compileTime.} =
+  newTree(nnkBracketExpr, newIdentNode(sv), newIdentNode("key"))
+
+proc stateDecl(n: NimNode; names: TableRef[string, bool]; decl, init: NimNode) =
+  case n.kind
+  of nnkVarSection, nnkLetSection:
+    for c in n:
+      expectKind c, nnkIdentDefs
+      let typ = c[^2]
+      let val = c[^1]
+      let usedType = if typ.kind != nnkEmpty: typ else: val
+      if usedType.kind == nnkEmpty:
+        error("cannot determine the variable's type", c)
+      for i in 0 .. c.len-3:
+        let v = $c[i]
+        let sv = toState v
+        decl.add quote do:
+          var `sv` = newJDict[VKey, `usedType`]()
+        if val.kind != nnkEmpty:
+          init.add newTree(nnkAsgn, accessState(sv), val)
+        names[v] = true
+  of nnkStmtList, nnkStmtListExpr:
+    for x in n: stateDecl(x, names, decl, init)
+  of nnkDo:
+    stateDecl(n.body, names, decl, init)
+  of nnkCommentStmt: discard
+  else:
+    error("invalid 'state' declaration", n)
+
+proc doState(n: NimNode; names: TableRef[string, bool];
+             decl, init: NimNode): NimNode =
+  result = n
+  case n.kind
+  of nnkCallKinds:
+    # handle 'state' declaration and remove it from the AST:
+    if n.len == 2 and repr(n[0]) == "state":
+      stateDecl(n[1], names, decl, init)
+      result = newTree(nnkEmpty)
+  of nnkSym, nnkIdent:
+    let v = $n
+    if v in names:
+      let sv = toState v
+      result = accessState(sv)
+  else:
+    for i in 0..<n.len:
+      result[i] = doState(n[i], names, decl, init)