[1851] fixed the label of textfield in form when its label position to start

[TheNoumanDev]

Ticket: #1851

Fixed an issue where form labels weren't updating their visibility state when the associated input field's visibility was toggled. While input fields correctly handled visibility changes, it was because the labels added separately in the form layout weren't being rebuilt again.

Changes made:

• Added ValueListenableBuilder in form's buildGrid method to rebuild the grid layout when properties change
• Added a formStateNotifier in FormController to track form state changes
• Implemented property change listener in TextInputState to notify form of any controller property updates
• Added mounted check before accessing context to prevent unmounted widget errors

Previously, changing an input field's visibility only affected the input itself, leaving its label in an inconsistent state. Now, the entire form grid rebuilds whenever any property changes, ensuring labels and inputs stay in sync.

Test EDL:

View:
  styles:
    useSafeArea: true
    backgroundColor: white

  header:
    titleText: Home
  body:
    Column:
      styles:
        padding: 24
        gap: 32
      children:
        - Button:
            label: Test
            onTap: |
              testInputA.visible = true;
              testInputB.visible = true;
        - Button:
            label: Test
            onTap: |
              testInputA.visible = false;
              testInputB.visible = false;
        - TextInput:
            label: I was invisible
            visible: false
            id: testInputA
        - Spacer:
            styles:
              size: 40
        - Form:
            styles:
              labelPosition: start
            children:
              - TextInput:
                  label: I was invisible
                  visible: false
                  id: testInputB

Bug:

Fixed:

[kmahmood74]

so the only change here is the ValueListenableBuilder(
valueListenable: widget._controller.formStateNotifier,

rest is the same right?

[TheNoumanDev]

Yes, rest is same, its just change bcz of indent.