Add an experimental plugin system for decorating OnPreDrawListener in Glide.

- This change introduces `GlidePlugins` to allow external code to provide a decorator function for `ViewTreeObserver.OnPreDrawListener` instances used by `ViewTarget` and `CustomViewTarget`.

PiperOrigin-RevId: 825163004

Author: falhassen

library/src/main/java/com/bumptech/glide/GlidePlugins.java

@@ -0,0 +1,39 @@
+package com.bumptech.glide;
+
+import android.view.ViewTreeObserver.OnPreDrawListener;
+import java.util.function.Function;
+
+/**
+ * A class for holding static methods that are used to globally modify the behavior of Glide. This
+ * class is used to allow apps to globally modify the behavior of Glide.
+ */
+public final class GlidePlugins {
+
+  private static Function<OnPreDrawListener, OnPreDrawListener> onPreDrawListenerDecorator = null;
+
+  /**
+   * Sets a decorator to be applied to all {@link OnPreDrawListener}s created by Glide.
+   *
+   * <p>This is intended to be used by apps that want to globally modify all {@link
+   * OnPreDrawListener}s created by Glide.
+   *
+   * <p>This is an experimental method that may be removed without warning in a future version.
+   */
+  public static void experimentalSetOnPreDrawListenerDecorator(
+      Function<OnPreDrawListener, OnPreDrawListener> decorator) {
+    onPreDrawListenerDecorator = decorator;
+  }
+
+  /**
+   * Returns the {@link OnPreDrawListener} provided, possibly after being decorated by {@link
+   * #experimentalSetOnPreDrawListenerDecorator(Function)}.
+   */
+  public static OnPreDrawListener decorateOnPreDrawListener(OnPreDrawListener listener) {
+    if (onPreDrawListenerDecorator == null) {
+      return listener;
+    }
+    return onPreDrawListenerDecorator.apply(listener);
+  }
+
+  private GlidePlugins() {}
+}

library/src/main/java/com/bumptech/glide/request/target/CustomViewTarget.java

@@ -14,6 +14,7 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
+import com.bumptech.glide.GlidePlugins;
 import com.bumptech.glide.R;
 import com.bumptech.glide.request.Request;
 import com.bumptech.glide.request.transition.Transition;
@@ -299,7 +300,7 @@ static final class SizeDeterminer {
     private final List<SizeReadyCallback> cbs = new ArrayList<>();
     @Synthetic boolean waitForLayout;
 
-    @Nullable private SizeDeterminerLayoutListener layoutListener;
+    @Nullable private ViewTreeObserver.OnPreDrawListener layoutListener;
 
     SizeDeterminer(@NonNull View view) {
       this.view = view;
@@ -359,7 +360,8 @@ void getSize(@NonNull SizeReadyCallback cb) {
       }
       if (layoutListener == null) {
         ViewTreeObserver observer = view.getViewTreeObserver();
-        layoutListener = new SizeDeterminerLayoutListener(this);
+        layoutListener =
+            GlidePlugins.decorateOnPreDrawListener(new SizeDeterminerLayoutListener(this));
         observer.addOnPreDrawListener(layoutListener);
       }
     }

library/src/main/java/com/bumptech/glide/request/target/ViewTarget.java

@@ -14,6 +14,7 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
+import com.bumptech.glide.GlidePlugins;
 import com.bumptech.glide.R;
 import com.bumptech.glide.request.Request;
 import com.bumptech.glide.util.Preconditions;
@@ -324,7 +325,7 @@ static final class SizeDeterminer {
     private final List<SizeReadyCallback> cbs = new ArrayList<>();
     @Synthetic boolean waitForLayout;
 
-    @Nullable private SizeDeterminerLayoutListener layoutListener;
+    @Nullable private ViewTreeObserver.OnPreDrawListener layoutListener;
 
     SizeDeterminer(@NonNull View view) {
       this.view = view;
@@ -384,7 +385,8 @@ void getSize(@NonNull SizeReadyCallback cb) {
       }
       if (layoutListener == null) {
         ViewTreeObserver observer = view.getViewTreeObserver();
-        layoutListener = new SizeDeterminerLayoutListener(this);
+        layoutListener =
+            GlidePlugins.decorateOnPreDrawListener(new SizeDeterminerLayoutListener(this));
         observer.addOnPreDrawListener(layoutListener);
       }
     }