Add interface to enable spans to pre and post draw on canvas

Summary: This diff introduces a new interface that can be used to process custom span that need to provide extra drawing capabilities as described in the [Composable Spans RFC](https://docs.google.com/document/d/1EKlAx9dMWsrltmmN1Ge9NfsXSycSXKwCLcmoCoxbwlE/edit#bookmark=id.hwdk13oj54fd)

Reviewed By: rooju

Differential Revision: D53533455

fbshipit-source-id: 3b26102e0e6af2fd977e4a3e6243c6b939db222c

litho-rendercore-text/BUCK

@@ -3,6 +3,7 @@ load(
     "//tools/build_defs/oss:litho_defs.bzl",
     "LITHO_ANDROIDSUPPORT_TARGET",
     "LITHO_INFERANNOTATIONS_TARGET",
+    "LITHO_RENDERCORE_PRIMITIVES_TARGET",
     "LITHO_RENDERCORE_TARGET",
     "LITHO_RENDERCORE_TEXT_TARGET",
     "LITHO_TEXTLAYOUTBUILDER_TARGET",
@@ -13,9 +14,12 @@ load(
 
 litho_android_library(
     name = "litho-rendercore-text",
-    srcs = glob(["src/main/java/**/*.java"]),
+    srcs = glob([
+        "src/main/java/**/*.java",
+        "src/main/java/**/*.kt",
+    ]),
     autoglob = False,
-    language = "JAVA",
+    pure_kotlin = False,
     visibility = [
         "PUBLIC",
     ],
@@ -25,6 +29,7 @@ litho_android_library(
         LITHO_TEXTLAYOUTBUILDER_TARGET,
         LITHO_ANDROIDSUPPORT_TARGET,
         LITHO_INFERANNOTATIONS_TARGET,
+        LITHO_RENDERCORE_PRIMITIVES_TARGET,
         "//fbandroid/android_res/rendercore:rendercore",
         "//fbandroid/java/com/facebook/proguard/annotations:annotations",
     ],

litho-rendercore-text/build.gradle

@@ -15,6 +15,7 @@
  */
 
 apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion rootProject.compileSdkVersion
@@ -33,6 +34,7 @@ android {
 }
 
 dependencies {
+    implementation project(':litho-rendercore-primitives')
     implementation project(':litho-rendercore-res')
     api project(':litho-rendercore')
 

litho-rendercore-text/src/main/java/com/facebook/rendercore/text/OnPrePostDrawSpan.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.facebook.rendercore.text
+
+import android.graphics.Canvas
+import android.text.Layout
+
+/**
+ * A span interface that allows users to receive callbacks with the [Canvas] so that extra drawing
+ * capabilities as made available through the composable and extensible spans styles.
+ */
+interface OnPrePostDrawSpan {
+  fun draw(
+      canvas: Canvas,
+      text: CharSequence,
+      start: Int,
+      end: Int,
+      layout: Layout,
+      drawCommand: Command
+  )
+
+  interface Command {
+    fun draw(canvas: Canvas)
+  }
+}

litho-rendercore-text/src/main/java/com/facebook/rendercore/text/RCTextView.java

@@ -40,6 +40,7 @@
 import android.view.View;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityNodeInfo;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.core.view.AccessibilityDelegateCompat;
 import androidx.core.view.ViewCompat;
@@ -51,7 +52,10 @@
 import com.facebook.rendercore.text.accessibility.RCAccessibleClickableSpan;
 import java.util.List;
 
-/** A pared-down TextView that only displays text. */
+/**
+ * A custom Android View that behaves like a TextView providing support for spans, custom drawing
+ * and truncations.
+ */
 @DoNotStrip
 public class RCTextView extends View {
   private static final String ACCESSIBILITY_CLASS_BUTTON = "android.widget.Button";
@@ -112,13 +116,59 @@ public void draw(Canvas canvas) {
       shouldRestore = true;
     }
 
-    mLayout.draw(canvas, getSelectionPath(), mHighlightPaint, 0);
+    final OnPrePostDrawSpan[] onPrePostDrawSpans = getOnPrePostDrawableSpans();
+    if (onPrePostDrawSpans.length == 0) {
+      drawLayout(canvas);
+    } else {
+      drawInternal(onPrePostDrawSpans, canvas);
+    }
 
     if (shouldRestore) {
       canvas.restoreToCount(saveCount);
     }
   }
 
+  private void drawInternal(final OnPrePostDrawSpan[] onOnPrePostDrawSpans, final Canvas canvas) {
+    OnPrePostDrawSpan.Command currentDrawAction =
+        new OnPrePostDrawSpan.Command() {
+          @Override
+          public void draw(@NonNull Canvas canvas) {
+            drawLayout(canvas);
+          }
+        };
+    final Spanned text = (Spanned) mText;
+    // OnPrePostDraw spans are retrieved in the same order in which they are applied (i.e. in order
+    // of pre-order traversal of the composable span tree).  We want to have their onDraw calls
+    // invoked in the same order.  In order to chain them in that order, we need to walk the spans
+    // list backward.
+    int length = onOnPrePostDrawSpans.length;
+    for (int i = length - 1; i >= 0; i--) {
+      OnPrePostDrawSpan onDraw = onOnPrePostDrawSpans[i];
+      OnPrePostDrawSpan.Command previousAction = currentDrawAction;
+      int spanStart = text.getSpanStart(onDraw);
+      int spanEnd = text.getSpanEnd(onDraw);
+      currentDrawAction =
+          new OnPrePostDrawSpan.Command() {
+            @Override
+            public void draw(@NonNull Canvas canvas) {
+              onDraw.draw(canvas, mText, spanStart, spanEnd, mLayout, previousAction);
+            }
+          };
+    }
+    currentDrawAction.draw(canvas);
+  }
+
+  private void drawLayout(Canvas canvas) {
+    mLayout.draw(canvas, getSelectionPath(), mHighlightPaint, 0);
+  }
+
+  private OnPrePostDrawSpan[] getOnPrePostDrawableSpans() {
+    if (!(mText instanceof Spanned)) {
+      return new OnPrePostDrawSpan[0];
+    }
+    return ((Spanned) mText).getSpans(0, mText.length(), OnPrePostDrawSpan.class);
+  }
+
   public void mount(TextLayout textLayout) {
     final ColorStateList colorStateList = textLayout.textStyle.textColorStateList;
     mText = textLayout.processedText;