Reshape text at runtime via ViewModel and animation without mutating the document

include/pagx/PAGComposition.h

@@ -38,6 +38,7 @@ class Composition;
 class DataBindRuntime;
 class DataContext;
 class Node;
+class TextHolder;
 struct RuntimeBinding;
 
 /**
@@ -123,7 +124,7 @@ class PAGComposition : public PAGLayer {
   // compositions themselves. Used by the composition-tree walks (view-model build, data-bind
   // update, view-model advance) so that compositions nested under plain container layers are not
   // skipped.
-  static void CollectChildCompositions(PAGLayer* layer, std::vector<PAGComposition*>& outChildren);
+  static void CollectChildCompositions(const PAGLayer* layer, std::vector<PAGComposition*>& outChildren);
 
   // Refreshes this composition after edits: reconciles its child layer list and refreshes any dirty
   // leaf layers in place, then recurses into child compositions. Called by PAGScene::onNodesChanged.
@@ -185,6 +186,12 @@ class PAGComposition : public PAGLayer {
 
   void updateDataBinds(float mix = 1.0f);
 
+  // Appends every TextHolder registered in this composition's binding and its descendant
+  // compositions to `out`. Used by PAGScene to maintain a flat list of all holders across the
+  // runtime tree so per-frame flush / dirty checks can iterate it directly instead of walking the
+  // composition tree every frame.
+  void collectTextHolders(std::vector<std::shared_ptr<TextHolder>>& out) const;
+
   friend class PAGScene;
 };
 

include/pagx/PAGScene.h

@@ -45,6 +45,7 @@ class PAGViewModel;
 class PAGXDocument;
 class SuppressDelegation;
 class PAGViewModelValue;
+class TextHolder;
 class ViewModel;
 class Image;
 struct Matrix;
@@ -156,9 +157,9 @@ class PAGScene : public std::enable_shared_from_this<PAGScene> {
   /**
    * Returns true if the scene's content has changed since the last render, i.e. a redraw would
    * produce different pixels. Hosts driving their own render loop can consult this to skip
-   * redundant full renders on idle frames. Reflects only the runtime layer tree state captured
-   * by the last renderTo()/Record(); pending ViewModel data binds flushed at the next Record()
-   * are not accounted for here.
+   * redundant full renders on idle frames. Returns true when either the underlying display list
+   * has changed or a pending TextHolder reshape (driven by a ViewModel data bind or animation
+   * text-shaping channel) has not yet been flushed — flush runs inside Record().
    */
   bool hasContentChanged() const;
 
@@ -215,6 +216,10 @@ class PAGScene : public std::enable_shared_from_this<PAGScene> {
       ViewModel* schema, const std::shared_ptr<PAGScene>& scene,
       std::unordered_set<const ViewModel*>& visited);
   void flushDataBinds();
+  void flushTextHolders();
+  // Rebuilds the flat `textHolders` list from the current runtime tree. Called at the end of
+  // buildRuntimeTree and after refreshNodes so the list stays in sync with the binding state.
+  void collectTextHolders();
   void clearAllViewModelsDirty();
   static void ClearCompositionTreeDirty(PAGComposition* comp);
 
@@ -251,6 +256,12 @@ class PAGScene : public std::enable_shared_from_this<PAGScene> {
   bool suppressNotify = false;
   std::vector<PAGViewModelValue*> pendingNotifications = {};
 
+  // Flat list of every TextHolder registered across the runtime composition tree. Rebuilt at the
+  // end of buildRuntimeTree and after refreshNodes (which can replace a binding's holders via
+  // RefreshLayerInPlace). flushTextHolders and hasContentChanged iterate this list directly so the
+  // common case (no text reshape in the document) avoids walking the composition tree every frame.
+  std::vector<std::shared_ptr<TextHolder>> textHolders = {};
+
   // Maps tgfx layers in the runtime tree to their PAGLayer nodes for hit-test resolution.
   std::unordered_map<const tgfx::Layer*, PAGLayer*> layerRegistry = {};
 

resources/text/text_reshape_demo.pagx

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<pagx width="400" height="200" viewModel="@MainVM">
+  <Resources>
+    <ViewModel id="MainVM">
+      <Property id="title" name="title" type="String" default="VM Default"/>
+      <Property id="size" name="size" type="Number" default="40"/>
+    </ViewModel>
+  </Resources>
+
+  <Layer id="animLayer" name="AnimText" width="400" height="100">
+    <Text id="animText" text="Hello" fontFamily="NotoSansSC" fontSize="40" position="20,70"/>
+    <Fill color="#000000"/>
+    <Timelines>
+      <Animation ref="@textAnim"/>
+    </Timelines>
+  </Layer>
+
+  <Layer id="vmLayer" name="VMText" width="400" height="100" y="100">
+    <Text id="vmText" text="VM Default" fontFamily="NotoSansSC" fontSize="40" position="20,170"/>
+    <Fill color="#0000FF"/>
+  </Layer>
+
+  <DataBind source="$vm.title" target="@vmText" channel="text"/>
+  <DataBind source="$vm.size" target="@vmText" channel="fontSize"/>
+
+  <Animations>
+    <Animation id="textAnim" duration="120" frameRate="60" loop="once">
+      <Object target="animText">
+        <Channel name="text" type="string">
+          <Key time="0" value="Hello" interpolation="hold"/>
+          <Key time="60" value="Animated" interpolation="hold"/>
+        </Channel>
+      </Object>
+    </Animation>
+  </Animations>
+</pagx>