add: subsribing to raw events in syntax suger for re-building changab…

…le childs

readme.md

@@ -352,7 +352,7 @@ elementsObj --- Layout():
         text = "+"
 ```
 
-The `<--- ctor: props[]...` syntax can be used to re-build tree based on property changes
+The `<--- ctor: prop[]; event[]; ...` syntax can be used to re-build tree based on property changes
 ```nim
 var elements = ["first", "second"].property
 var elementsObj: CustomProperty[Layout]

src/sigui/events.nim

@@ -201,3 +201,7 @@ template connectTo*(s: var Event[void], obj: var EventHandler, argname: untyped,
 proc hasHandlers*(e: Event): bool =
   if e.p == nil: return false
   e.p.connected.len > 0
+
+
+template changed*[T](e: Event[T]): Event[T] =
+  e

tests/t_todoapp.nim

@@ -5,15 +5,24 @@ import siwin
 import sigui
 import t_customComponent
 
-type App = ref object of Uiobj
-  tasks: seq[tuple[name: string, complete: Property[bool]]]
-  tasksChanged: Event[void]
+type
+  App = ref object of Uiobj
+    tasks: seq[tuple[name: string, complete: Property[bool]]]
+    tasksChanged: Event[void]
 
-  layout: CustomProperty[Layout]
+    layout: CustomProperty[Layout]
+
+  DestroyLogger = object
+    message: string
 
 registerComponent App
 
 
+proc `=destroy`(x: DestroyLogger) =
+  if x.message != "":
+    echo x.message
+
+
 test "todo app":
   let window = newOpenglWindow(size = ivec2(500, 800), title = "todos").newUiWindow
 
@@ -84,6 +93,8 @@ test "todo app":
       top = taskAdder.bottom + 20
 
       app.layout --- Layout():
+        <--- Layout(): app.tasksChanged[]
+
         this.binding w: parent.w[]
 
         orientation = vertical
@@ -92,6 +103,8 @@ test "todo app":
         for i in 0..app.tasks.high:
           template task: auto = app.tasks[i]
 
+          let logger {.used.} = DestroyLogger(message: "destroyed: " & $i)
+
           - Layout():
             spacing = 10
             align = center
@@ -119,8 +132,6 @@ test "todo app":
                 this.fill parent
                 this.mouseDownAndUpInside.connectTo this:
                   task.complete[] = not task.complete[]
-
-    app.tasksChanged.connectTo app:
-      app.layout[] = Layout()
+                  echo "made sure ", logger.message, " works"
 
   run window.siwinWindow