Editor implementation

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+# 4.2.0-SNAPSHOT
+* `MarkwonEditor` to highlight markdown input whilst editing (new module: `markwon-editor`)
+* `Markwon#configuration` method to expose `MarkwonConfiguration` via public API
+* `HeadingSpan#getLevel` getter
+
 # 4.1.2
 * Do not re-use RenderProps when creating a new visitor (fixes [#171])
 

app/build.gradle

@@ -24,10 +24,17 @@ android {
             proguardFile 'proguard.pro'
         }
     }
+
+    compileOptions {
+        targetCompatibility '1.8'
+        sourceCompatibility '1.8'
+    }
 }
 
 dependencies {
 
+    implementation project(':markwon-editor')
+
     implementation project(':markwon-core')
     implementation project(':markwon-ext-strikethrough')
     implementation project(':markwon-ext-tables')

app/src/main/AndroidManifest.xml

@@ -53,6 +53,11 @@
 
         </activity>
 
+        <activity
+            android:name=".edit.EditActivity"
+            android:exported="true"
+            android:windowSoftInputMode="adjustResize" />
+
     </application>
 
 </manifest>

app/src/main/java/io/noties/markwon/app/edit/EditActivity.java

@@ -0,0 +1,185 @@
+package io.noties.markwon.app.edit;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.text.Editable;
+import android.text.Spanned;
+import android.text.TextPaint;
+import android.text.style.ForegroundColorSpan;
+import android.text.style.MetricAffectingSpan;
+import android.text.style.UnderlineSpan;
+import android.widget.EditText;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import java.util.concurrent.Executors;
+
+import io.noties.debug.AndroidLogDebugOutput;
+import io.noties.debug.Debug;
+import io.noties.markwon.Markwon;
+import io.noties.markwon.app.R;
+import io.noties.markwon.core.MarkwonTheme;
+import io.noties.markwon.core.spans.BlockQuoteSpan;
+import io.noties.markwon.core.spans.CodeBlockSpan;
+import io.noties.markwon.core.spans.CodeSpan;
+import io.noties.markwon.core.spans.LinkSpan;
+import io.noties.markwon.core.spans.StrongEmphasisSpan;
+import io.noties.markwon.editor.MarkwonEditor;
+import io.noties.markwon.editor.MarkwonEditorTextWatcher;
+
+public class EditActivity extends Activity {
+
+    static {
+        Debug.init(new AndroidLogDebugOutput(true));
+    }
+//
+//    private static final String S = "**bold** it seems to **work** for now, new lines are cool to certain extend **yo**!\n" +
+//            "\n" +
+//            "> quote!\n" +
+//            "> > nested quote!\n" +
+//            "\n" +
+//            "**bold** man, make it bold!\n" +
+//            "\n" +
+//            "# Head\n" +
+//            "## Head\n" +
+//            "\n" +
+//            "man, **crazy** thing called love.... **work**, **work** **work** man, super weird,\n" +
+//            "\n" +
+//            "`code`, yeah and code doesn't work\n" +
+//            "\n" +
+//            "* one\n" +
+//            "* two\n" +
+//            "* three\n" +
+//            "* * hey!\n" +
+//            "   * super hey\n" +
+//            "\n" +
+//            "it does seem good **bold**, now shifted... **bold** man, now restored **bold** *em* sd\n" +
+//            "\n" +
+//            "[link](#) is it? ![image](./png) hey! **bold**\n" +
+//            "\n";
+
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_edit);
+
+        final EditText editText = findViewById(R.id.edit_text);
+
+        final Markwon markwon = Markwon.create(this);
+        final MarkwonTheme theme = markwon.configuration().theme();
+
+        final MarkwonEditor editor = MarkwonEditor.builder(markwon)
+                .withPunctuationSpan(MarkdownPunctuationSpan.class, MarkdownPunctuationSpan::new)
+                .includeEditSpan(Bold.class, Bold::new)
+                .includeEditSpan(CodeSpan.class, () -> new CodeSpan(theme))
+                .includeEditSpan(UnderlineSpan.class, UnderlineSpan::new)
+                .includeEditSpan(CodeBlockSpan.class, () -> new CodeBlockSpan(theme))
+                .includeEditSpan(BlockQuoteSpan.class, () -> new BlockQuoteSpan(theme))
+                .withEditSpanHandlerFor(StrongEmphasisSpan.class, new MarkwonEditor.EditSpanHandler<StrongEmphasisSpan>() {
+                    @Override
+                    public void handle(@NonNull MarkwonEditor.SpanStore store, @NonNull Editable editable, @NonNull String input, @NonNull StrongEmphasisSpan span, int spanStart, int spanTextLength) {
+                        editable.setSpan(
+                                store.get(Bold.class),
+                                spanStart,
+                                // we know that strong emphasis is delimited with 2 characters on both sides
+                                spanStart + spanTextLength + 4,
+                                Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                        );
+                    }
+                })
+                .withEditSpanHandlerFor(LinkSpan.class, new MarkwonEditor.EditSpanHandler<LinkSpan>() {
+                    @Override
+                    public void handle(@NonNull MarkwonEditor.SpanStore store, @NonNull Editable editable, @NonNull String input, @NonNull LinkSpan span, int spanStart, int spanTextLength) {
+                        editable.setSpan(
+                                store.get(UnderlineSpan.class),
+                                // add underline only for link text
+                                spanStart + 1,
+                                spanStart + 1 + spanTextLength,
+                                Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                        );
+                    }
+                })
+                .withEditSpanHandlerFor(CodeSpan.class, new MarkwonEditor.EditSpanHandler<CodeSpan>() {
+                    @Override
+                    public void handle(@NonNull MarkwonEditor.SpanStore store, @NonNull Editable editable, @NonNull String input, @NonNull CodeSpan span, int spanStart, int spanTextLength) {
+                        editable.setSpan(
+                                store.get(CodeSpan.class),
+                                spanStart,
+                                spanStart + spanTextLength,
+                                Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                        );
+                    }
+                })
+                .withEditSpanHandlerFor(CodeBlockSpan.class, new MarkwonEditor.EditSpanHandler<CodeBlockSpan>() {
+                    @Override
+                    public void handle(@NonNull MarkwonEditor.SpanStore store, @NonNull Editable editable, @NonNull String input, @NonNull CodeBlockSpan span, int spanStart, int spanTextLength) {
+                        // if starts with backticks -> count them and then add everything until the line end
+                        if (input.charAt(spanStart) == '`') {
+                            final int firstLineEnd = input.indexOf('\n', spanStart);
+                            if (firstLineEnd == -1) return;
+                            int lastLineEnd = input.indexOf('\n', spanStart + (firstLineEnd - spanStart) + spanTextLength + 1);
+                            if (lastLineEnd == -1) lastLineEnd = input.length();
+
+                            editable.setSpan(
+                                    store.get(CodeBlockSpan.class),
+                                    spanStart,
+                                    lastLineEnd,
+                                    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                            );
+                        } else {
+                            // todo: just everything until the end
+                            editable.setSpan(
+                                    store.get(CodeBlockSpan.class),
+                                    spanStart,
+                                    spanStart + spanTextLength,
+                                    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                            );
+                        }
+                    }
+                })
+                .withEditSpanHandlerFor(BlockQuoteSpan.class, new MarkwonEditor.EditSpanHandler<BlockQuoteSpan>() {
+                    @Override
+                    public void handle(@NonNull MarkwonEditor.SpanStore store, @NonNull Editable editable, @NonNull String input, @NonNull BlockQuoteSpan span, int spanStart, int spanTextLength) {
+                        editable.setSpan(
+                                store.get(BlockQuoteSpan.class),
+                                spanStart,
+                                spanStart + spanTextLength,
+                                Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                        );
+                    }
+                })
+                .build();
+
+        editText.addTextChangedListener(MarkwonEditorTextWatcher.withPreRender(
+                editor,
+                Executors.newCachedThreadPool(),
+                editText));
+    }
+
+    private static class MarkdownPunctuationSpan extends ForegroundColorSpan {
+        MarkdownPunctuationSpan() {
+            super(0xFFFF0000);
+        }
+    }
+
+    private static class Bold extends MetricAffectingSpan {
+        public Bold() {
+            super();
+        }
+
+        @Override
+        public void updateDrawState(TextPaint tp) {
+            update(tp);
+        }
+
+        @Override
+        public void updateMeasureState(@NonNull TextPaint textPaint) {
+            update(textPaint);
+        }
+
+        private void update(@NonNull TextPaint paint) {
+            paint.setFakeBoldText(true);
+        }
+    }
+}

app/src/main/res/layout/activity_edit.xml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:padding="8dip">
+
+    <EditText
+        android:id="@+id/edit_text"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:autofillHints="none"
+        android:hint="Message..."
+        android:maxLines="100"
+        android:inputType="text|textLongMessage|textMultiLine" />
+
+</FrameLayout>

markwon-core/src/main/java/io/noties/markwon/Markwon.java

@@ -134,6 +134,9 @@ public abstract class Markwon {
     @NonNull
     public abstract List<? extends MarkwonPlugin> getPlugins();
 
+    @NonNull
+    public abstract MarkwonConfiguration configuration();
+
     /**
      * Interface to set text on a TextView. Primary goal is to give a way to use PrecomputedText
      * functionality
@@ -141,21 +144,21 @@ public abstract class Markwon {
      * @see PrecomputedTextSetterCompat
      * @since 4.1.0
      */
-public interface TextSetter {
-    /**
-     * @param textView   TextView
-     * @param markdown   prepared markdown
-     * @param bufferType BufferType specified when building {@link Markwon} instance
-     *                   via {@link Builder#bufferType(TextView.BufferType)}
-     * @param onComplete action to run when set-text is finished (required to call in order
-     *                   to execute {@link MarkwonPlugin#afterSetText(TextView)})
-     */
-    void setText(
-            @NonNull TextView textView,
-            @NonNull Spanned markdown,
-            @NonNull TextView.BufferType bufferType,
-            @NonNull Runnable onComplete);
-}
+    public interface TextSetter {
+        /**
+         * @param textView   TextView
+         * @param markdown   prepared markdown
+         * @param bufferType BufferType specified when building {@link Markwon} instance
+         *                   via {@link Builder#bufferType(TextView.BufferType)}
+         * @param onComplete action to run when set-text is finished (required to call in order
+         *                   to execute {@link MarkwonPlugin#afterSetText(TextView)})
+         */
+        void setText(
+                @NonNull TextView textView,
+                @NonNull Spanned markdown,
+                @NonNull TextView.BufferType bufferType,
+                @NonNull Runnable onComplete);
+    }
 
     /**
      * Builder for {@link Markwon}.

markwon-core/src/main/java/io/noties/markwon/MarkwonBuilderImpl.java

@@ -113,6 +113,7 @@ class MarkwonBuilderImpl implements Markwon.Builder {
                 textSetter,
                 parserBuilder.build(),
                 visitorFactory,
+                configuration,
                 Collections.unmodifiableList(plugins)
         );
     }

markwon-core/src/main/java/io/noties/markwon/MarkwonImpl.java

@@ -21,6 +21,7 @@ class MarkwonImpl extends Markwon {
     private final TextView.BufferType bufferType;
     private final Parser parser;
     private final MarkwonVisitorFactory visitorFactory; // @since 4.1.1
+    private final MarkwonConfiguration configuration;
     private final List<MarkwonPlugin> plugins;
 
     // @since 4.1.0
@@ -32,11 +33,13 @@ class MarkwonImpl extends Markwon {
             @Nullable TextSetter textSetter,
             @NonNull Parser parser,
             @NonNull MarkwonVisitorFactory visitorFactory,
+            @NonNull MarkwonConfiguration configuration,
             @NonNull List<MarkwonPlugin> plugins) {
         this.bufferType = bufferType;
         this.textSetter = textSetter;
         this.parser = parser;
         this.visitorFactory = visitorFactory;
+        this.configuration = configuration;
         this.plugins = plugins;
     }
 
@@ -154,4 +157,10 @@ class MarkwonImpl extends Markwon {
     public List<? extends MarkwonPlugin> getPlugins() {
         return Collections.unmodifiableList(plugins);
     }
+
+    @NonNull
+    @Override
+    public MarkwonConfiguration configuration() {
+        return configuration;
+    }
 }

markwon-core/src/main/java/io/noties/markwon/core/spans/HeadingSpan.java

@@ -77,4 +77,11 @@ public class HeadingSpan extends MetricAffectingSpan implements LeadingMarginSpa
             }
         }
     }
+
+    /**
+     * @since 4.2.0-SNAPSHOT
+     */
+    public int getLevel() {
+        return level;
+    }
 }

markwon-editor/README.md

@@ -0,0 +1,6 @@
+# Editor
+
+Markdown editor for Android based on `Markwon`.
+
+Main principle: _difference_ between input text and rendered markdown is considered to be
+_punctuation_. 

markwon-editor/build.gradle

@@ -0,0 +1,32 @@
+apply plugin: 'com.android.library'
+
+android {
+
+    compileSdkVersion config['compile-sdk']
+    buildToolsVersion config['build-tools']
+
+    defaultConfig {
+        minSdkVersion config['min-sdk']
+        targetSdkVersion config['target-sdk']
+        versionCode 1
+        versionName version
+    }
+}
+
+dependencies {
+
+    api project(':markwon-core')
+
+    deps['test'].with {
+
+        testImplementation project(':markwon-test-span')
+
+        testImplementation it['junit']
+        testImplementation it['robolectric']
+        testImplementation it['mockito']
+
+        testImplementation it['commons-io']
+    }
+}
+
+registerArtifact(this)

markwon-editor/gradle.properties

@@ -0,0 +1,4 @@
+POM_NAME=Editor
+POM_ARTIFACT_ID=editor
+POM_DESCRIPTION=Markdown editor based on Markwon
+POM_PACKAGING=aar

markwon-editor/src/main/AndroidManifest.xml

@@ -0,0 +1 @@
+<manifest package="io.noties.markwon.editor" />

markwon-editor/src/main/java/io/noties/markwon/editor/EditSpanHandlerBuilder.java

@@ -0,0 +1,44 @@
+package io.noties.markwon.editor;
+
+import android.text.Editable;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import java.util.HashMap;
+import java.util.Map;
+
+class EditSpanHandlerBuilder {
+
+    private final Map<Class<?>, MarkwonEditor.EditSpanHandler> map = new HashMap<>(3);
+
+    <T> void include(@NonNull Class<T> type, @NonNull MarkwonEditor.EditSpanHandler<T> handler) {
+        map.put(type, handler);
+    }
+
+    @Nullable
+    MarkwonEditor.EditSpanHandler build() {
+        if (map.size() == 0) {
+            return null;
+        }
+        return new EditSpanHandlerImpl(map);
+    }
+
+    private static class EditSpanHandlerImpl implements MarkwonEditor.EditSpanHandler {
+
+        private final Map<Class<?>, MarkwonEditor.EditSpanHandler> map;
+
+        EditSpanHandlerImpl(@NonNull Map<Class<?>, MarkwonEditor.EditSpanHandler> map) {
+            this.map = map;
+        }
+
+        @Override
+        public void handle(@NonNull MarkwonEditor.SpanStore store, @NonNull Editable editable, @NonNull String input, @NonNull Object span, int spanStart, int spanTextLength) {
+            final MarkwonEditor.EditSpanHandler handler = map.get(span.getClass());
+            if (handler != null) {
+                //noinspection unchecked
+                handler.handle(store, editable, input, span, spanStart, spanTextLength);
+            }
+        }
+    }
+}

markwon-editor/src/main/java/io/noties/markwon/editor/MarkwonEditor.java

@@ -0,0 +1,160 @@
+package io.noties.markwon.editor;
+
+import android.text.Editable;
+
+import androidx.annotation.NonNull;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import io.noties.markwon.Markwon;
+
+// todo: if multiple spans are used via factory... only the first one is delivered to edit-span-handler
+//  does it though? yeah... only the first one and then break... deliver all?
+
+// todo: how to reuse existing spanFactories? to obtain a value they require render-props....
+//  maybe.. mock them? plus, spanFactory can return multiple spans
+
+// todo: we can actually create punctuation span with reasonable defaults to be used by default
+
+/**
+ * @since 4.2.0-SNAPSHOT
+ */
+public abstract class MarkwonEditor {
+
+    public interface SpanStore {
+
+        /**
+         * If a span of specified type was not registered with {@link Builder#includeEditSpan(Class, SpanFactory)}
+         * then an exception is raised.
+         *
+         * @param type of a span to obtain
+         * @return cached or newly created span
+         */
+        @NonNull
+        <T> T get(Class<T> type);
+    }
+
+    public interface SpanFactory<T> {
+        @NonNull
+        T create();
+    }
+
+    public interface EditSpanHandler<T> {
+        void handle(
+                @NonNull SpanStore store,
+                @NonNull Editable editable,
+                @NonNull String input,
+                @NonNull T span,
+                int spanStart,
+                int spanTextLength);
+    }
+
+    public interface PreRenderResult {
+
+        // With which pre-render method was called as input
+        @NonNull
+        Editable resultEditable();
+
+        void dispatchTo(@NonNull Editable editable);
+    }
+
+    public interface PreRenderResultListener {
+        void onPreRenderResult(@NonNull PreRenderResult result);
+    }
+
+    @NonNull
+    public static Builder builder(@NonNull Markwon markwon) {
+        return new Builder(markwon);
+    }
+
+    /**
+     * Synchronous method that processes supplied Editable in-place. If you wish to move this job
+     * to another thread consider using {@link #preRender(Editable, PreRenderResultListener)}
+     *
+     * @param editable to process
+     * @see #preRender(Editable, PreRenderResultListener)
+     */
+    public abstract void process(@NonNull Editable editable);
+
+    /**
+     * Please note that currently only `setSpan` and `removeSpan` actions will be recorded (and thus dispatched).
+     * make sure you use only these methods in your {@link EditSpanHandler}, or implement the required
+     * functionality in some other way.
+     *
+     * @param editable          to process and pre-render
+     * @param preRenderListener listener to be notified when pre-render result will be ready
+     * @see #process(Editable)
+     */
+    public abstract void preRender(@NonNull Editable editable, @NonNull PreRenderResultListener preRenderListener);
+
+    public static class Builder {
+
+        private final Markwon markwon;
+        private final EditSpanHandlerBuilder editSpanHandlerBuilder = new EditSpanHandlerBuilder();
+
+        private Class<?> punctuationSpanType;
+        private Map<Class<?>, SpanFactory> spans = new HashMap<>(3);
+
+        Builder(@NonNull Markwon markwon) {
+            this.markwon = markwon;
+        }
+
+        /**
+         * The only required argument which will make {@link MarkwonEditor} apply specified span only
+         * to markdown punctuation
+         *
+         * @param type    of the span
+         * @param factory to create a new instance of the span
+         */
+        @NonNull
+        public <T> Builder withPunctuationSpan(@NonNull Class<T> type, @NonNull SpanFactory<T> factory) {
+            this.punctuationSpanType = type;
+            this.spans.put(type, factory);
+            return this;
+        }
+
+        /**
+         * Include specific span that will be used in highlighting. It is important to understand
+         * that it is not the span that is used by Markwon, but instead your own span that you
+         * apply in a custom {@link EditSpanHandler} specified by {@link #withEditSpanHandlerFor(Class, EditSpanHandler)}.
+         * You can apply a Markwon bundled span (or any other) but it must be still explicitly
+         * included by this method.
+         * <p>
+         * The span will be exposed via {@link SpanStore} in your custom {@link EditSpanHandler}.
+         * If you do not use a custom {@link EditSpanHandler} you do not need to specify any span here.
+         *
+         * @param type    of a span to include
+         * @param factory to create a new instance of a span if one is missing from processed Editable
+         */
+        @NonNull
+        public <T> Builder includeEditSpan(
+                @NonNull Class<T> type,
+                @NonNull SpanFactory<T> factory) {
+            this.spans.put(type, factory);
+            return this;
+        }
+
+        @NonNull
+        public <T> Builder withEditSpanHandlerFor(@NonNull Class<T> type, @NonNull EditSpanHandler<T> editSpanHandler) {
+            this.editSpanHandlerBuilder.include(type, editSpanHandler);
+            return this;
+        }
+
+        @NonNull
+        public MarkwonEditor build() {
+
+            final Class<?> punctuationSpanType = this.punctuationSpanType;
+            if (punctuationSpanType == null) {
+                throw new IllegalStateException("Punctuation span type is required, " +
+                        "add with Builder#withPunctuationSpan method");
+            }
+
+            return new MarkwonEditorImpl(
+                    markwon,
+                    spans,
+                    punctuationSpanType,
+                    editSpanHandlerBuilder.build());
+        }
+    }
+}

markwon-editor/src/main/java/io/noties/markwon/editor/MarkwonEditorImpl.java

@@ -0,0 +1,237 @@
+package io.noties.markwon.editor;
+
+import android.text.Editable;
+import android.text.Spannable;
+import android.text.SpannableStringBuilder;
+import android.text.Spanned;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import io.noties.markwon.Markwon;
+import io.noties.markwon.editor.diff_match_patch.Diff;
+
+class MarkwonEditorImpl extends MarkwonEditor {
+
+    private final Markwon markwon;
+    private final Map<Class<?>, SpanFactory> spans;
+    private final Class<?> punctuationSpanType;
+
+    @Nullable
+    private final EditSpanHandler editSpanHandler;
+
+    MarkwonEditorImpl(
+            @NonNull Markwon markwon,
+            @NonNull Map<Class<?>, SpanFactory> spans,
+            @NonNull Class<?> punctuationSpanType,
+            @Nullable EditSpanHandler editSpanHandler) {
+        this.markwon = markwon;
+        this.spans = spans;
+        this.punctuationSpanType = punctuationSpanType;
+        this.editSpanHandler = editSpanHandler;
+    }
+
+    @Override
+    public void process(@NonNull Editable editable) {
+
+        final String input = editable.toString();
+        final Spanned renderedMarkdown = markwon.toMarkdown(input);
+        final String markdown = renderedMarkdown.toString();
+
+        final EditSpanHandler editSpanHandler = this.editSpanHandler;
+        final boolean hasAdditionalSpans = editSpanHandler != null;
+
+        final SpanStoreImpl store = new SpanStoreImpl(editable, spans);
+        try {
+
+            final List<Diff> diffs = diff_match_patch.diff_main(input, markdown);
+
+            int inputLength = 0;
+            int markdownLength = 0;
+
+            for (Diff diff : diffs) {
+
+                switch (diff.operation) {
+
+                    case DELETE:
+
+                        final int start = inputLength;
+                        inputLength += diff.text.length();
+                        editable.setSpan(
+                                store.get(punctuationSpanType),
+                                start,
+                                inputLength,
+                                Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+                        );
+
+                        if (hasAdditionalSpans) {
+                            final Object[] spans = renderedMarkdown.getSpans(markdownLength, markdownLength + 1, Object.class);
+                            for (Object span : spans) {
+                                if (markdownLength == renderedMarkdown.getSpanStart(span)) {
+                                    editSpanHandler.handle(
+                                            store,
+                                            editable,
+                                            input,
+                                            span,
+                                            start,
+                                            renderedMarkdown.getSpanEnd(span) - markdownLength);
+                                }
+                            }
+                        }
+                        break;
+
+                    case INSERT:
+                        markdownLength += diff.text.length();
+                        break;
+
+                    case EQUAL:
+                        final int length = diff.text.length();
+                        inputLength += length;
+                        markdownLength += length;
+                        break;
+
+                    default:
+                        throw new IllegalStateException();
+                }
+            }
+
+        } finally {
+            store.removeUnused();
+        }
+    }
+
+    @Override
+    public void preRender(@NonNull final Editable editable, @NonNull PreRenderResultListener listener) {
+        final RecordingSpannableStringBuilder builder = new RecordingSpannableStringBuilder(editable);
+        process(builder);
+        listener.onPreRenderResult(new PreRenderResult() {
+            @NonNull
+            @Override
+            public Editable resultEditable() {
+                // if they are the same, they should be equals then (what about additional spans?? like cursor? it should not interfere....)
+                return builder;
+            }
+
+            @Override
+            public void dispatchTo(@NonNull Editable e) {
+                for (Span span : builder.applied) {
+                    e.setSpan(span.what, span.start, span.end, span.flags);
+                }
+                for (Object span : builder.removed) {
+                    e.removeSpan(span);
+                }
+            }
+        });
+    }
+
+    @NonNull
+    static Map<Class<?>, List<Object>> extractSpans(@NonNull Spanned spanned, @NonNull Collection<Class<?>> types) {
+
+        final Object[] spans = spanned.getSpans(0, spanned.length(), Object.class);
+        final Map<Class<?>, List<Object>> map = new HashMap<>(3);
+
+        Class<?> type;
+
+        for (Object span : spans) {
+            type = span.getClass();
+            if (types.contains(type)) {
+                List<Object> list = map.get(type);
+                if (list == null) {
+                    list = new ArrayList<>(3);
+                    map.put(type, list);
+                }
+                list.add(span);
+            }
+        }
+
+        return map;
+    }
+
+    static class SpanStoreImpl implements SpanStore {
+
+        private final Spannable spannable;
+        private final Map<Class<?>, SpanFactory> spans;
+        private final Map<Class<?>, List<Object>> map;
+
+        SpanStoreImpl(@NonNull Spannable spannable, @NonNull Map<Class<?>, SpanFactory> spans) {
+            this.spannable = spannable;
+            this.spans = spans;
+            this.map = extractSpans(spannable, spans.keySet());
+        }
+
+        @NonNull
+        @Override
+        public <T> T get(Class<T> type) {
+
+            final Object span;
+
+            final List<Object> list = map.get(type);
+            if (list != null && list.size() > 0) {
+                span = list.remove(0);
+            } else {
+                final SpanFactory spanFactory = spans.get(type);
+                if (spanFactory == null) {
+                    throw new IllegalStateException("Requested type `" + type.getName() + "` was " +
+                            "not registered, use Builder#includeEditSpan method to register");
+                }
+                span = spanFactory.create();
+            }
+
+            //noinspection unchecked
+            return (T) span;
+        }
+
+        void removeUnused() {
+            for (List<Object> spans : map.values()) {
+                if (spans != null
+                        && spans.size() > 0) {
+                    for (Object span : spans) {
+                        spannable.removeSpan(span);
+                    }
+                }
+            }
+        }
+    }
+
+    private static class Span {
+        final Object what;
+        final int start;
+        final int end;
+        final int flags;
+
+        Span(Object what, int start, int end, int flags) {
+            this.what = what;
+            this.start = start;
+            this.end = end;
+            this.flags = flags;
+        }
+    }
+
+    private static class RecordingSpannableStringBuilder extends SpannableStringBuilder {
+
+        final List<Span> applied = new ArrayList<>(3);
+        final List<Object> removed = new ArrayList<>(0);
+
+        RecordingSpannableStringBuilder(CharSequence text) {
+            super(text);
+        }
+
+        @Override
+        public void setSpan(Object what, int start, int end, int flags) {
+            super.setSpan(what, start, end, flags);
+            applied.add(new Span(what, start, end, flags));
+        }
+
+        @Override
+        public void removeSpan(Object what) {
+            super.removeSpan(what);
+            removed.add(what);
+        }
+    }
+}

markwon-editor/src/main/java/io/noties/markwon/editor/MarkwonEditorTextWatcher.java

@@ -0,0 +1,140 @@
+package io.noties.markwon.editor;
+
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.view.View;
+import android.widget.EditText;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+
+/**
+ * Implementation of TextWatcher that uses {@link MarkwonEditor#process(Editable)} method
+ * to apply markdown highlighting right after text changes.
+ *
+ * @see MarkwonEditor#process(Editable)
+ * @see MarkwonEditor#preRender(Editable, MarkwonEditor.PreRenderResultListener)
+ * @since 4.2.0-SNAPSHOT
+ */
+public abstract class MarkwonEditorTextWatcher implements TextWatcher {
+
+    @NonNull
+    public static MarkwonEditorTextWatcher withProcess(@NonNull MarkwonEditor editor) {
+        return new WithProcess(editor);
+    }
+
+    @NonNull
+    public static MarkwonEditorTextWatcher withPreRender(
+            @NonNull MarkwonEditor editor,
+            @NonNull ExecutorService executorService,
+            @NonNull EditText editText) {
+        return new WithPreRender(editor, executorService, editText);
+    }
+
+    @Override
+    public abstract void afterTextChanged(Editable s);
+
+    @Override
+    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
+
+    }
+
+    @Override
+    public void onTextChanged(CharSequence s, int start, int before, int count) {
+
+    }
+
+
+    static class WithProcess extends MarkwonEditorTextWatcher {
+
+        private final MarkwonEditor editor;
+
+        private boolean selfChange;
+
+        public WithProcess(@NonNull MarkwonEditor editor) {
+            this.editor = editor;
+        }
+
+        @Override
+        public void afterTextChanged(Editable s) {
+
+            if (selfChange) {
+                return;
+            }
+
+            selfChange = true;
+            try {
+                editor.process(s);
+            } finally {
+                selfChange = false;
+            }
+        }
+    }
+
+    static class WithPreRender extends MarkwonEditorTextWatcher {
+
+        private final MarkwonEditor editor;
+        private final ExecutorService executorService;
+
+        @Nullable
+        private EditText editText;
+
+        private Future<?> future;
+
+        WithPreRender(
+                @NonNull MarkwonEditor editor,
+                @NonNull ExecutorService executorService,
+                @NonNull EditText editText) {
+            this.editor = editor;
+            this.executorService = executorService;
+            this.editText = editText;
+            this.editText.addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
+                @Override
+                public void onViewAttachedToWindow(View v) {
+
+                }
+
+                @Override
+                public void onViewDetachedFromWindow(View v) {
+                    WithPreRender.this.editText = null;
+                }
+            });
+        }
+
+        @Override
+        public void afterTextChanged(final Editable s) {
+
+            // todo: maybe checking hash is not so performant?
+            //   what if we create a atomic reference and use it (with tag applied to editText)?
+
+            if (future != null) {
+                future.cancel(true);
+            }
+
+            future = executorService.submit(new Runnable() {
+                @Override
+                public void run() {
+                    editor.preRender(s, new MarkwonEditor.PreRenderResultListener() {
+                        @Override
+                        public void onPreRenderResult(@NonNull final MarkwonEditor.PreRenderResult result) {
+                            if (editText != null) {
+                                final int key = result.resultEditable().toString().hashCode();
+                                editText.post(new Runnable() {
+                                    @Override
+                                    public void run() {
+                                        if (key == editText.getText().toString().hashCode()) {
+                                            result.dispatchTo(editText.getText());
+                                        }
+                                    }
+                                });
+                            }
+                        }
+                    });
+                }
+            });
+        }
+    }
+}

markwon-linkify/src/main/java/io/noties/markwon/linkify/LinkifyPlugin.java

@@ -52,6 +52,7 @@ public class LinkifyPlugin extends AbstractMarkwonPlugin {
         });
     }
 
+    // todo: thread safety (builder is reused)
     private static class LinkifyTextAddedListener implements CorePlugin.OnTextAddedListener {
 
         private final int mask;

settings.gradle

@@ -1,6 +1,7 @@
 rootProject.name = 'MarkwonProject'
 include ':app', ':sample',
         ':markwon-core',
+        ':markwon-editor',
         ':markwon-ext-latex',
         ':markwon-ext-strikethrough',
         ':markwon-ext-tables',