feat: add undo/redo support for view attributes

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/adapters/ViewAttrListAdapter.kt

@@ -41,7 +41,7 @@ import com.itsaky.androidide.utils.DialogUtils
  *
  * @author Akash Yadav
  */
-class ViewAttrListAdapter(
+internal class ViewAttrListAdapter(
   attributes: List<IAttribute>,
   private val viewModel: WorkspaceViewModel?,
   private val onDeleteAttr: (IAttribute) -> Boolean,

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/adapters/WidgetsCategoryAdapter.kt

@@ -27,7 +27,7 @@ import com.itsaky.androidide.uidesigner.models.UiWidgetCategory
 import com.itsaky.androidide.uidesigner.viewmodel.WorkspaceViewModel
 
 /** @author Akash Yadav */
-class WidgetsCategoryAdapter(categories: List<UiWidgetCategory>, private val viewModel: WorkspaceViewModel) : RecyclerView.Adapter<VH>() {
+internal class WidgetsCategoryAdapter(categories: List<UiWidgetCategory>, private val viewModel: WorkspaceViewModel) : RecyclerView.Adapter<VH>() {
 
   private val categories =
     categories.let {

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/adapters/WidgetsItemAdapter.kt

@@ -29,7 +29,7 @@ import com.itsaky.androidide.uidesigner.drag.WidgetDragShadowBuilder
 import com.itsaky.androidide.uidesigner.viewmodel.WorkspaceViewModel
 
 /** @author Akash Yadav */
-class WidgetsItemAdapter(
+internal class WidgetsItemAdapter(
   private val widgets: List<UiWidget>,
   private val viewModel : WorkspaceViewModel
 ) : RecyclerView.Adapter<VH>() {

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/fragments/DesignerWorkspaceFragment.kt

@@ -81,6 +81,7 @@ class DesignerWorkspaceFragment : BaseFragment() {
   }
 
   private val hierarchyHandler by lazy { WorkspaceViewHierarchyHandler() }
+  private val attrHandler by lazy { WorkspaceViewAttrHandler() }
   private val inflationHandler by lazy { WorkspaceLayoutInflationHandler() }
 
   companion object {
@@ -99,6 +100,7 @@ class DesignerWorkspaceFragment : BaseFragment() {
   ): View {
     this.binding = FragmentDesignerWorkspaceBinding.inflate(inflater, container, false)
     hierarchyHandler.init(this)
+    attrHandler.init(this)
     inflationHandler.init(this)
     return this.binding!!.root
   }
@@ -130,11 +132,13 @@ class DesignerWorkspaceFragment : BaseFragment() {
     super.onDestroyView()
     this.binding = null
     this.hierarchyHandler.release()
+    this.attrHandler.release()
     this.inflationHandler.release()
     this.inflater.close()
   }
 
   internal fun setupView(view: IView) {
+    view.registerAttributeChangeListener(attrHandler)
     view.view.setOnTouchListener(
       WidgetTouchListener(view, requireContext()) {
         viewModel.view = it

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/fragments/ViewInfoFragment.kt

@@ -27,8 +27,10 @@ import com.google.android.material.bottomsheet.BottomSheetDialogFragment
 import com.itsaky.androidide.uidesigner.adapters.ViewAttrListAdapter
 import com.itsaky.androidide.uidesigner.databinding.LayoutViewInfoBinding
 import com.itsaky.androidide.uidesigner.databinding.LayoutViewInfoHeaderBinding
+import com.itsaky.androidide.uidesigner.models.UiAttribute
 import com.itsaky.androidide.uidesigner.viewmodel.WorkspaceViewModel
 import com.itsaky.androidide.uidesigner.viewmodel.WorkspaceViewModel.Companion.SCREEN_VALUE_EDITOR
+import com.itsaky.androidide.uidesigner.viewmodel.WorkspaceViewModel.Companion.SCREEN_VIEW_INFO
 
 /**
  * A [BottomSheetDialogFragment] which shows information about a clicked view.
@@ -68,6 +70,12 @@ class ViewInfoFragment : Fragment() {
   override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
     super.onViewCreated(view, savedInstanceState)
     viewModel._view.observe(viewLifecycleOwner) { showViewInfo() }
+    viewModel._viewInfoScreen.observe(viewLifecycleOwner) {
+      viewModel.undoManager.enabled = it != SCREEN_VALUE_EDITOR
+      if (it == SCREEN_VIEW_INFO) {
+        viewModel.notifyAttrUpdated()
+      }
+    }
   }
 
   override fun onDestroyView() {
@@ -83,11 +91,17 @@ class ViewInfoFragment : Fragment() {
     header.name.text = view.simpleName
     header.desc.text = view.name
     binding.attrList.adapter =
-      ViewAttrListAdapter(attributes = view.attributes, viewModel = viewModel, onDeleteAttr = {
-        view.removeAttribute(it)
-        true
-      }) {
-        viewModel.selectedAttr = it
+      ViewAttrListAdapter(
+        attributes = view.attributes,
+        viewModel = viewModel,
+        onDeleteAttr = {
+          view.removeAttribute(it)
+          true
+        }
+      ) {
+        // Store a copy of the attribute so that we can check if the value of the attribute has changed in WorkspaceViewModel.notifyAttrUpdated()
+        //
+        viewModel.selectedAttr = (it as UiAttribute).copyAttr()
         viewModel.viewInfoScreen = SCREEN_VALUE_EDITOR
       }
 

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/fragments/ViewInfoSheet.kt

@@ -17,6 +17,7 @@
 
 package com.itsaky.androidide.uidesigner.fragments
 
+import android.content.DialogInterface
 import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
@@ -49,6 +50,12 @@ class ViewInfoSheet : BottomSheetDialogFragment() {
         }
       }
     }
+  
+  override fun onDismiss(dialog: DialogInterface) {
+    viewModel.undoManager.enable()
+    viewModel.notifyAttrUpdated()
+    super.onDismiss(dialog)
+  }
 
   override fun onCreateView(
     inflater: LayoutInflater,

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/fragments/WorkspaceLayoutInflationHandler.kt

@@ -45,9 +45,11 @@ class WorkspaceLayoutInflationHandler : IInflateEventsListener {
     val frag = this.fragment ?: return
     if (event is InflationStartEvent) {
       frag.isInflating = true
+      frag.undoManager.disable()
     }
     if (event is InflationFinishEvent) {
       frag.isInflating = false
+      frag.undoManager.enable()
     }
     if (event is OnInflateViewEvent) {
       frag.setupView(event.data)

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/fragments/WorkspaceViewAttrHandler.kt

@@ -0,0 +1,64 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.uidesigner.fragments
+
+import com.itsaky.androidide.inflater.IAttribute
+import com.itsaky.androidide.inflater.IView
+import com.itsaky.androidide.uidesigner.models.UiAttribute
+import com.itsaky.androidide.uidesigner.undo.AttrAddedAction
+import com.itsaky.androidide.uidesigner.undo.AttrRemovedAction
+import com.itsaky.androidide.uidesigner.undo.AttrUpdatedAction
+
+/**
+ * Handles view attribute changes in [DesignerWorkspaceFragment].
+ *
+ * @author Akash Yadav
+ */
+internal class WorkspaceViewAttrHandler : IView.AttributeChangeListener {
+
+  private var fragment: DesignerWorkspaceFragment? = null
+
+  internal fun init(fragment: DesignerWorkspaceFragment) {
+    this.fragment = fragment
+  }
+
+  internal fun release() {
+    this.fragment = null
+  }
+
+  override fun onAttributeAdded(view: IView, attribute: IAttribute) {
+    val frag = this.fragment ?: return
+    frag.undoManager.push(AttrAddedAction(view = view, attr = attribute as UiAttribute))
+  }
+
+  override fun onAttributeRemoved(view: IView, attribute: IAttribute) {
+    val frag = this.fragment ?: return
+    frag.undoManager.push(AttrRemovedAction(view = view, attr = attribute as UiAttribute))
+  }
+
+  override fun onAttributeUpdated(view: IView, attribute: IAttribute, oldValue: String) {
+    val frag = this.fragment ?: return
+    frag.undoManager.push(
+      AttrUpdatedAction(
+        view = view,
+        attr = (attribute as UiAttribute).copyAttr(view = view) as UiAttribute,
+        oldValue = oldValue
+      )
+    )
+  }
+}

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/models/UiAttribute.kt

@@ -28,7 +28,7 @@ import com.itsaky.androidide.inflater.internal.ViewAdapterIndex
  *
  * @author Akash Yadav
  */
-internal data class UiAttribute
+internal open class UiAttribute
 @JvmOverloads
 constructor(
   override val namespace: INamespace = INamespace.ANDROID,

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/undo/AttrAction.kt

@@ -0,0 +1,29 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.uidesigner.undo
+
+import com.itsaky.androidide.inflater.IAttribute
+import com.itsaky.androidide.inflater.IView
+import com.itsaky.androidide.uidesigner.models.UiAttribute
+
+/**
+ * [UndoManager] action related to view attributes.
+ *
+ * @author Akash Yadav
+ */
+internal abstract class AttrAction(protected val view: IView, protected val attr: UiAttribute) : IUiAction

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/undo/AttrAddedAction.kt

@@ -0,0 +1,37 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.uidesigner.undo
+
+import com.itsaky.androidide.inflater.IView
+import com.itsaky.androidide.uidesigner.models.UiAttribute
+
+/**
+ * Represents the action when the user adds an attribute to an [IView].
+ *
+ * @author Akash Yadav
+ */
+internal class AttrAddedAction(view: IView, attr: UiAttribute) : AttrAction(view, attr) {
+
+  override fun undo() {
+    view.removeAttribute(attr)
+  }
+
+  override fun redo() {
+    view.addAttribute(attr, true)
+  }
+}

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/undo/AttrRemovedAction.kt

@@ -0,0 +1,37 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.uidesigner.undo
+
+import com.itsaky.androidide.inflater.IView
+import com.itsaky.androidide.uidesigner.models.UiAttribute
+
+/**
+ * Represents the action when the user removes an attribute from an [IView].
+ *
+ * @author Akash Yadav
+ */
+internal class AttrRemovedAction(view: IView, attr: UiAttribute) : AttrAction(view, attr) {
+
+  override fun undo() {
+    view.addAttribute(attr)
+  }
+
+  override fun redo() {
+    view.removeAttribute(attr)
+  }
+}

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/undo/AttrUpdatedAction.kt

@@ -0,0 +1,40 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  AndroidIDE is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.itsaky.androidide.uidesigner.undo
+
+import com.itsaky.androidide.inflater.IView
+import com.itsaky.androidide.uidesigner.models.UiAttribute
+
+/**
+ * Represents the action when the user updates an attribute in an [IView].
+ *
+ * @author Akash Yadav
+ */
+internal class AttrUpdatedAction(view: IView, attr: UiAttribute, private val oldValue: String) :
+  AttrAction(view, attr) {
+
+  override fun undo() {
+    // NOTE : We need to provide the view instance so that the new attribute object created will be
+    // an instance of UiAttribute
+    view.updateAttribute(attr.copyAttr(view = view, value = oldValue))
+  }
+
+  override fun redo() {
+    view.updateAttribute(attr)
+  }
+}

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/undo/UndoManager.kt

@@ -25,7 +25,6 @@ package com.itsaky.androidide.uidesigner.undo
 class UndoManager @JvmOverloads constructor(private var maxStackSize: Int = DEFAULT_STACK_SIZE) {
 
   internal var enabled = true
-    private set
 
   private var undoStack = ArrayDeque<IUiAction>()
   private var redoStack = ArrayDeque<IUiAction>()

uidesigner/src/main/java/com/itsaky/androidide/uidesigner/viewmodel/WorkspaceViewModel.kt

@@ -21,10 +21,13 @@ import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
 import com.itsaky.androidide.inflater.IAttribute
 import com.itsaky.androidide.inflater.IView
+import com.itsaky.androidide.uidesigner.models.UiAttribute
+import com.itsaky.androidide.uidesigner.undo.AttrUpdatedAction
 import com.itsaky.androidide.uidesigner.undo.UndoManager
+import com.itsaky.androidide.utils.ILogger
 import java.io.File
 
-class WorkspaceViewModel : ViewModel() {
+internal class WorkspaceViewModel : ViewModel() {
   internal val _drawerOpened = MutableLiveData(false)
   internal val _errText = MutableLiveData("")
   internal val _workspaceScreen = MutableLiveData(SCREEN_WORKSPACE)
@@ -40,7 +43,7 @@ class WorkspaceViewModel : ViewModel() {
     const val SCREEN_VIEW_INFO = 0
     const val SCREEN_VALUE_EDITOR = 1
   }
-  
+
   val undoManager: UndoManager
     get() = this._undoManager.value!!
 
@@ -80,10 +83,26 @@ class WorkspaceViewModel : ViewModel() {
     set(value) {
       _viewInfoScreen.value = value
     }
-  
+
   var selectedAttr: IAttribute?
     get() = this._selectedAttr.value
     set(value) {
       this._selectedAttr.value = value
     }
+
+  fun notifyAttrUpdated() {
+    val attr = this.selectedAttr ?: return
+    val view = this.view ?: return
+    val undoManager = this.undoManager
+
+    val existing = view.findAttribute(attr.namespace.uri, attr.name)
+
+    if (existing !is UiAttribute || existing.value == attr.value) {
+      // value of the attribute is same as before
+      return
+    }
+
+    undoManager.push(AttrUpdatedAction(view, existing.copyAttr(view = view) as UiAttribute, attr.value))
+    this.selectedAttr = null
+  }
 }

uidesigner/src/test/java/com/itsaky/androidide/uidesigner/UiDesignerTest.kt

@@ -17,11 +17,49 @@
 
 package com.itsaky.androidide.uidesigner
 
+import android.content.Context
+import android.view.View
+import android.widget.LinearLayout
 import androidx.appcompat.app.AppCompatActivity
+import com.itsaky.androidide.inflater.IComponentFactory.Companion.LAYOUT_INFLATER_COMPONENT_FACTORY_KEY
+import com.itsaky.androidide.inflater.IViewGroup
+import com.itsaky.androidide.inflater.internal.LayoutFile
+import com.itsaky.androidide.inflater.internal.ViewGroupImpl
+import com.itsaky.androidide.inflater.internal.ViewImpl
+import com.itsaky.androidide.inflater.internal.utils.ViewFactory
+import com.itsaky.androidide.inflater.viewGroup
+import com.itsaky.androidide.lookup.Lookup
+import com.itsaky.androidide.uidesigner.utils.UiInflaterComponentFactory
+import java.io.File
 import org.robolectric.Robolectric
 
 private val activity by lazy { Robolectric.buildActivity(AppCompatActivity::class.java).get() }
 
-fun requiresActivity(block: AppCompatActivity.() -> Unit) {
+fun requiresActivity(initComponentFactory: Boolean = true, block: AppCompatActivity.() -> Unit) {
+  if (initComponentFactory) {
+    Lookup.DEFAULT.apply {
+      lookup(LAYOUT_INFLATER_COMPONENT_FACTORY_KEY)
+        ?: register(LAYOUT_INFLATER_COMPONENT_FACTORY_KEY, UiInflaterComponentFactory())
+    }
+  }
   activity.block()
-}
+}
+
+fun Context.createLayout(parent: IViewGroup? = null): ViewGroupImpl {
+  return ViewGroupImpl(
+      LayoutFile(File(""), ""),
+      LinearLayout::class.qualifiedName!!,
+      LinearLayout(this)
+    )
+    .apply { parent?.let { applyLayoutParams(it) } }
+}
+
+fun Context.createView(parent: IViewGroup? = null): ViewImpl {
+  return ViewImpl(LayoutFile(File(""), ""), View::class.qualifiedName!!, View(this)).apply {
+    parent?.let { applyLayoutParams(it) }
+  }
+}
+
+fun ViewImpl.applyLayoutParams(parent: IViewGroup) {
+  view.layoutParams = ViewFactory.generateLayoutParams(parent.viewGroup)
+}

uidesigner/src/test/java/com/itsaky/androidide/uidesigner/undo/UndoManagerTest.kt

@@ -17,14 +17,11 @@
 
 package com.itsaky.androidide.uidesigner.undo
 
-import android.view.View
-import android.widget.LinearLayout
 import com.google.common.truth.Truth.assertThat
-import com.itsaky.androidide.inflater.internal.LayoutFile
-import com.itsaky.androidide.inflater.internal.ViewGroupImpl
-import com.itsaky.androidide.inflater.internal.ViewImpl
+import com.itsaky.androidide.uidesigner.createView
+import com.itsaky.androidide.uidesigner.createLayout
+import com.itsaky.androidide.uidesigner.models.UiAttribute
 import com.itsaky.androidide.uidesigner.requiresActivity
-import java.io.File
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
@@ -36,8 +33,8 @@ class UndoManagerTest {
   @Test
   fun `test single view addition undo redo`() {
     requiresActivity {
-      val parent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
-      val child = ViewImpl(LayoutFile(File(""), ""), "", View(this))
+      val parent = createLayout()
+      val child = createView(parent = parent)
       val undoManager = UndoManager()
 
       assertThat(undoManager.canUndo()).isFalse()
@@ -72,8 +69,8 @@ class UndoManagerTest {
   @Test
   fun `test single view removal undo redo`() {
     requiresActivity {
-      val parent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
-      val child = ViewImpl(LayoutFile(File(""), ""), "", View(this))
+      val parent = createLayout()
+      val child = createView(parent = parent)
       val undoManager = UndoManager()
 
       parent.addChild(child)
@@ -102,22 +99,21 @@ class UndoManagerTest {
       assertThat(parent.childCount).isEqualTo(0)
     }
   }
-  
+
   @Test
   fun `test undo redo when view moved from one parent to another`() {
     requiresActivity {
-      val firstParent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
-      val secondParent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
-      val child = ViewImpl(LayoutFile(File(""), ""), "", View(this))
+      val firstParent = createLayout()
+      val secondParent = createLayout()
+      val child = createView(parent = firstParent)
       val undoManager = UndoManager()
-      
+
       // view initially added to first parent
       firstParent.addChild(child)
       assertThat(firstParent.childCount).isEqualTo(1)
       assertThat(secondParent.childCount).isEqualTo(0)
       assertThat(firstParent[0]).isEqualTo(child)
-      
-      
+
       // view moved to second parent
       child.removeFromParent()
       secondParent.addChild(child)
@@ -127,7 +123,7 @@ class UndoManagerTest {
       assertThat(firstParent.childCount).isEqualTo(0)
       assertThat(secondParent.childCount).isEqualTo(1)
       assertThat(secondParent[0]).isEqualTo(child)
-      
+
       // undo the last action
       // this should move child from secondParent to firstParent
       undoManager.undo()
@@ -136,7 +132,7 @@ class UndoManagerTest {
       assertThat(firstParent.childCount).isEqualTo(1)
       assertThat(secondParent.childCount).isEqualTo(0)
       assertThat(firstParent[0]).isEqualTo(child)
-  
+
       // redo the last action
       // this should move child from firstParent to secondParent
       undoManager.redo()
@@ -151,8 +147,8 @@ class UndoManagerTest {
   @Test
   fun `test actions not redoable after new action push`() {
     requiresActivity {
-      val parent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
-      val child = ViewImpl(LayoutFile(File(""), ""), "", View(this))
+      val parent = createLayout()
+      val child = createView(parent = parent)
       val undoManager = UndoManager()
 
       // --------------------------------------------------------
@@ -180,9 +176,9 @@ class UndoManagerTest {
   @Test
   fun `test multiple view undo redo`() {
     requiresActivity {
-      val parent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
-      val firstChild = ViewImpl(LayoutFile(File(""), ""), "", View(this))
-      val secondChild = ViewImpl(LayoutFile(File(""), ""), "", View(this))
+      val parent = createLayout()
+      val firstChild = createView(parent = parent)
+      val secondChild = createView(parent = parent)
       val undoManager = UndoManager()
 
       assertThat(undoManager.canUndo()).isFalse()
@@ -233,16 +229,16 @@ class UndoManagerTest {
   @Test
   fun `test indexed child addition and removal`() {
     requiresActivity {
-      val parent = ViewGroupImpl(LayoutFile(File(""), ""), "", LinearLayout(this))
+      val parent = createLayout()
       val undoManager = UndoManager()
 
       for (i in 1..5) {
-        parent.addChild(ViewImpl(LayoutFile(File(""), ""), "", View(this)))
+        parent.addChild(createView(parent = parent))
       }
 
       assertThat(parent.childCount).isEqualTo(5)
 
-      val child = ViewImpl(LayoutFile(File(""), ""), "", View(this))
+      val child = createView(parent = parent)
 
       parent.addChild(3, child)
       undoManager.push(ViewAddedAction(child, parent))
@@ -267,4 +263,106 @@ class UndoManagerTest {
       assertThat(parent[3]).isEqualTo(child)
     }
   }
+
+  @Test
+  fun `test undo and redo for simple view attr addition`() {
+    requiresActivity {
+      val child = createView(parent = createLayout())
+      val attr = UiAttribute(name = "layout_height", value = "match_parent")
+      val undoManager = UndoManager()
+
+      child.addAttribute(attr)
+      undoManager.push(AttrAddedAction(child, attr))
+
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isTrue()
+      assertThat(undoManager.canRedo()).isFalse()
+
+      undoManager.undo()
+      assertThat(child.attributes).hasSize(0)
+      assertThat(undoManager.canUndo()).isFalse()
+      assertThat(undoManager.canRedo()).isTrue()
+
+      undoManager.redo()
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isTrue()
+      assertThat(undoManager.canRedo()).isFalse()
+    }
+  }
+
+  @Test
+  fun `test undo and redo for simple view attr removal`() {
+    requiresActivity {
+      val child = createView(parent = createLayout())
+      val attr = UiAttribute(name = "layout_height", value = "match_parent")
+      val undoManager = UndoManager()
+
+      undoManager.push(AttrRemovedAction(child, attr))
+
+      assertThat(child.attributes).hasSize(0)
+      assertThat(undoManager.canUndo()).isTrue()
+      assertThat(undoManager.canRedo()).isFalse()
+
+      undoManager.undo()
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isFalse()
+      assertThat(undoManager.canRedo()).isTrue()
+
+      undoManager.redo()
+      assertThat(child.attributes).hasSize(0)
+      assertThat(undoManager.canUndo()).isTrue()
+      assertThat(undoManager.canRedo()).isFalse()
+    }
+  }
+
+  @Test
+  fun `test undo and redo for simple view attr update`() {
+    requiresActivity {
+      val child = createView(parent = createLayout())
+      val attr = UiAttribute(name = "layout_height", value = "match_parent").immutable()
+      val undoManager = UndoManager()
+      
+      child.addAttribute(UiAttribute(attr))
+
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isFalse()
+      assertThat(undoManager.canRedo()).isFalse()
+      child.findAttribute(attr.namespace.uri, attr.name).apply {
+        assertThat(this).isNotNull()
+        assertThat(this!!.value).isEqualTo("match_parent")
+      }
+
+      val copy = UiAttribute(attr).apply {
+        value = "wrap_content"
+      }
+      child.updateAttribute(copy)
+      undoManager.push(AttrUpdatedAction(child, copy, attr.value))
+
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isTrue()
+      assertThat(undoManager.canRedo()).isFalse()
+      child.findAttribute(attr.namespace.uri, attr.name).apply {
+        assertThat(this).isNotNull()
+        assertThat(this!!.value).isEqualTo("wrap_content")
+      }
+
+      undoManager.undo()
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isFalse()
+      assertThat(undoManager.canRedo()).isTrue()
+      child.findAttribute(attr.namespace.uri, attr.name).apply {
+        assertThat(this).isNotNull()
+        assertThat(this!!.value).isEqualTo("match_parent")
+      }
+
+      undoManager.redo()
+      assertThat(child.attributes).hasSize(1)
+      assertThat(undoManager.canUndo()).isTrue()
+      assertThat(undoManager.canRedo()).isFalse()
+      child.findAttribute(attr.namespace.uri, attr.name).apply {
+        assertThat(this).isNotNull()
+        assertThat(this!!.value).isEqualTo("wrap_content")
+      }
+    }
+  }
 }

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/AttributeImpl.kt

@@ -21,7 +21,7 @@ import com.itsaky.androidide.inflater.IAttribute
 import com.itsaky.androidide.inflater.INamespace
 import com.itsaky.androidide.inflater.INamespace.Companion.ANDROID
 import com.itsaky.androidide.inflater.IView
-import com.itsaky.androidide.inflater.newAttribute
+import com.itsaky.androidide.inflater.utils.newAttribute
 
 open class AttributeImpl
 @JvmOverloads
@@ -41,7 +41,7 @@ constructor(
     return newAttribute(view = view, namespace = namespace, name = name, value = value)
   }
 
-  internal fun immutableCopy(): IAttribute {
+  fun immutable(): IAttribute {
     return ImmutableAttributeImpl(this)
   }
 

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/ImmutableAttributeImpl.kt

@@ -24,7 +24,7 @@ import com.itsaky.androidide.inflater.IAttribute
  *
  * @author Akash Yadav
  */
-internal class ImmutableAttributeImpl(private val src: AttributeImpl) : IAttribute by src {
+class ImmutableAttributeImpl(private val src: AttributeImpl) : IAttribute by src {
   override var value: String
     get() = src.value
     set(value) {

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/ImmutableViewImpl.kt

@@ -28,7 +28,7 @@ import com.itsaky.androidide.inflater.IViewGroup
  *
  * @author Akash Yadav
  */
-internal class ImmutableViewImpl(private val src: ViewImpl) : IView by src {
+class ImmutableViewImpl(private val src: ViewImpl) : IView by src {
   
   override fun addAttribute(attribute: IAttribute, update: Boolean) {
     throw UnsupportedOperationException("Immutable!")

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/ViewGroupImpl.kt

@@ -105,7 +105,7 @@ open class ViewGroupImpl(file: LayoutFile, name: String, view: ViewGroup) :
     this.hierarchyChangeListeners.forEach { it.onViewRemoved(this, child, index) }
   }
 
-  override fun immutableCopy(): IViewGroup {
+  override fun immutable(): IViewGroup {
     return ImmutableViewGroupImpl(this)
   }
 }

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/ViewImpl.kt

@@ -94,6 +94,10 @@ constructor(
   }
   
   override fun registerAttributeChangeListener(listener: AttributeChangeListener) {
+    if (this.attrChangeListeners.contains(listener)) {
+      log.warn("Attempt to register an already-registered AttributeChangeListener")
+      return
+    }
     this.attrChangeListeners.add(listener)
   }
   
@@ -122,6 +126,10 @@ constructor(
   fun findNamespaceByUri(uri: String): INamespace? {
     return this.namespaceDecls[uri] ?: (parent as? ViewImpl)?.findNamespaceByUri(uri)
   }
+  
+  open fun immutable() : IView {
+    return ImmutableViewImpl(this)
+  }
 
   protected open fun hasAttribute(attribute: IAttribute): Boolean {
     return hasAttribute(attribute.namespace.uri, attribute.name)
@@ -141,10 +149,6 @@ constructor(
     builder.append("\n")
   }
   
-  internal open fun immutableCopy() : IView {
-    return ImmutableViewImpl(this)
-  }
-  
   private fun updateAttributeInternal(attribute: IAttribute, notify: Boolean = true) {
     val existing =
       findAttribute(attribute)

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/adapters/TextViewAttrAdapter.kt

@@ -30,7 +30,7 @@ import com.itsaky.androidide.inflater.IAttribute
 import com.itsaky.androidide.inflater.INamespace
 import com.itsaky.androidide.inflater.IView
 import com.itsaky.androidide.inflater.internal.LayoutFile
-import com.itsaky.androidide.inflater.newAttribute
+import com.itsaky.androidide.inflater.utils.newAttribute
 import java.util.regex.Pattern
 
 /**

xml-inflater/src/main/java/com/itsaky/androidide/inflater/internal/adapters/ViewAttrAdapter.kt

@@ -38,7 +38,7 @@ import com.itsaky.androidide.inflater.IView
 import com.itsaky.androidide.inflater.IViewAdapter
 import com.itsaky.androidide.inflater.internal.LayoutFile
 import com.itsaky.androidide.inflater.internal.ViewImpl
-import com.itsaky.androidide.inflater.newAttribute
+import com.itsaky.androidide.inflater.utils.newAttribute
 
 /**
  * Attribute adapter for [View].

xml-inflater/src/main/java/com/itsaky/androidide/inflater/utils/inflaterUtils.kt

@@ -15,14 +15,20 @@
  *   along with AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package com.itsaky.androidide.inflater
+package com.itsaky.androidide.inflater.utils
 
+import com.itsaky.androidide.inflater.IAttribute
+import com.itsaky.androidide.inflater.IComponentFactory
+import com.itsaky.androidide.inflater.ILayoutInflater
+import com.itsaky.androidide.inflater.ILayoutInflater.Companion
+import com.itsaky.androidide.inflater.INamespace
+import com.itsaky.androidide.inflater.IView
 import com.itsaky.androidide.inflater.internal.AttributeImpl
 import com.itsaky.androidide.lookup.Lookup
 
 /** Get the [ILayoutInflater] registered with [Lookup]. */
 fun lookupLayoutInflater(): ILayoutInflater? {
-  return Lookup.DEFAULT.lookup(ILayoutInflater.LOOKUP_KEY)
+  return Lookup.DEFAULT.lookup(Companion.LOOKUP_KEY)
 }
 
 /** Get the [IComponentFactory] registered with [Lookup]. */

xml-inflater/src/test/java/com/itsaky/androidide/inflater/LayoutInflaterTest.kt

@@ -24,6 +24,7 @@ import com.itsaky.androidide.inflater.internal.LayoutInflaterImpl
 import com.itsaky.androidide.inflater.internal.ViewGroupImpl
 import com.itsaky.androidide.inflater.internal.ViewImpl
 import com.itsaky.androidide.inflater.internal.utils.IDTable
+import com.itsaky.androidide.inflater.utils.newAttribute
 import com.itsaky.androidide.projects.ProjectManager
 import com.itsaky.androidide.projects.api.AndroidModule
 import org.junit.Test