disable save button when there are no pending note type changes

Author: sanjaysargam

AnkiDroid/src/main/java/com/ichi2/anki/dialogs/ChangeNoteTypeDialog.kt

@@ -152,10 +152,15 @@ class ChangeNoteTypeDialog : AnalyticsDialogFragment(R.layout.dialog_change_note
         }
     }
 
+    private fun updateSaveButton(binding: DialogChangeNoteTypeBinding) {
+        binding.btnSave.isEnabled = viewModel.hasChanges()
+    }
+
     private fun setupChangeNoteTypeDialog(binding: DialogChangeNoteTypeBinding) {
         Timber.d("setting up dialog")
         setupNoteTypeSpinner(binding)
         setupViewPagerAndTabs(binding)
+        updateSaveButton(binding)
     }
 
     private fun setupNoteTypeSpinner(binding: DialogChangeNoteTypeBinding) {
@@ -168,6 +173,7 @@ class ChangeNoteTypeDialog : AnalyticsDialogFragment(R.layout.dialog_change_note
             onItemSelectedListener =
                 BasicItemSelectedListener { position, id: NoteTypeId ->
                     viewModel.setOutputNoteTypeId(id)
+                    updateSaveButton(binding)
                 }
         }
     }
@@ -410,6 +416,10 @@ class ChangeNoteTypeDialog : AnalyticsDialogFragment(R.layout.dialog_change_note
                                         SelectedIndex.from(position)
                                     }
                                 viewModel.updateFieldMapping(oldIndex, newMapping)
+                                (requireParentFragment() as ChangeNoteTypeDialog)
+                                    .updateSaveButton(
+                                        DialogChangeNoteTypeBinding.bind(requireParentFragment().requireView()),
+                                    )
                             }
                     }
 
@@ -601,6 +611,10 @@ class ChangeNoteTypeDialog : AnalyticsDialogFragment(R.layout.dialog_change_note
                                         SelectedIndex.from(position)
                                     }
                                 viewModel.updateTemplateMapping(outputTemplateIndex = spinnerIndex, newMapping)
+                                (requireParentFragment() as ChangeNoteTypeDialog)
+                                    .updateSaveButton(
+                                        DialogChangeNoteTypeBinding.bind(requireParentFragment().requireView()),
+                                    )
                             }
                     }
 

AnkiDroid/src/main/java/com/ichi2/anki/dialogs/ChangeNoteTypeViewModel.kt

@@ -300,6 +300,22 @@ class ChangeNoteTypeViewModel(
         }
     }
 
+    /**
+     * Returns whether there are any pending changes in Change Note Type.
+     *
+     * Save button should only be enabled when:
+     * - note type is changed
+     * - field mapping is changed
+     * - template mapping is changed
+     *
+     * If everything is same as the initial/default state,
+     * then there is nothing to save.
+     */
+    fun hasChanges(): Boolean =
+        inputNoteType.id != outputNoteType.id ||
+            fieldChangeMap != rebuildFieldMap(outputNoteType) ||
+            templateChangeMap != rebuildTemplateMap(outputNoteType)
+
     /**
      * Performs the [changeNoteTypeOfNotes] operation
      *