Sample, add heading handler

sample/src/main/java/io/noties/markwon/sample/editor/EditorActivity.java

@@ -64,7 +64,8 @@ public class EditorActivity extends ActivityWithMenuOptions {
                 .add("multipleEditSpans", this::multiple_edit_spans)
                 .add("multipleEditSpansPlugin", this::multiple_edit_spans_plugin)
                 .add("pluginRequire", this::plugin_require)
-                .add("pluginNoDefaults", this::plugin_no_defaults);
+                .add("pluginNoDefaults", this::plugin_no_defaults)
+                .add("heading", this::heading);
     }
 
     @Override
@@ -317,6 +318,16 @@ public class EditorActivity extends ActivityWithMenuOptions {
                 editor, Executors.newSingleThreadExecutor(), editText));
     }
 
+    private void heading() {
+        final Markwon markwon = Markwon.create(this);
+        final MarkwonEditor editor = MarkwonEditor.builder(markwon)
+                .useEditHandler(new HeadingEditHandler())
+                .build();
+
+        editText.addTextChangedListener(MarkwonEditorTextWatcher.withPreRender(
+                editor, Executors.newSingleThreadExecutor(), editText));
+    }
+
     private void initBottomBar() {
         // all except block-quote wraps if have selection, or inserts at current cursor position
 

sample/src/main/java/io/noties/markwon/sample/editor/HeadingEditHandler.java

@@ -0,0 +1,78 @@
+package io.noties.markwon.sample.editor;
+
+import android.text.Editable;
+import android.text.Spanned;
+
+import androidx.annotation.NonNull;
+
+import io.noties.markwon.Markwon;
+import io.noties.markwon.core.MarkwonTheme;
+import io.noties.markwon.core.spans.HeadingSpan;
+import io.noties.markwon.editor.EditHandler;
+import io.noties.markwon.editor.PersistedSpans;
+
+public class HeadingEditHandler implements EditHandler<HeadingSpan> {
+
+    private MarkwonTheme theme;
+
+    @Override
+    public void init(@NonNull Markwon markwon) {
+        this.theme = markwon.configuration().theme();
+    }
+
+    @Override
+    public void configurePersistedSpans(@NonNull PersistedSpans.Builder builder) {
+        builder
+                .persistSpan(Head1.class, () -> new Head1(theme))
+                .persistSpan(Head2.class, () -> new Head2(theme));
+    }
+
+    @Override
+    public void handleMarkdownSpan(
+            @NonNull PersistedSpans persistedSpans,
+            @NonNull Editable editable,
+            @NonNull String input,
+            @NonNull HeadingSpan span,
+            int spanStart,
+            int spanTextLength
+    ) {
+        final Class<?> type;
+        switch (span.getLevel()) {
+            case 1: type = Head1.class; break;
+            case 2: type = Head2.class; break;
+            default:
+                type = null;
+        }
+
+        if (type != null) {
+            final int index = input.indexOf('\n', spanStart + spanTextLength);
+            final int end = index < 0
+                    ? input.length()
+                    : index;
+            editable.setSpan(
+                    persistedSpans.get(type),
+                    spanStart,
+                    end,
+                    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
+            );
+        }
+    }
+
+    @NonNull
+    @Override
+    public Class<HeadingSpan> markdownSpanType() {
+        return HeadingSpan.class;
+    }
+
+    private static class Head1 extends HeadingSpan {
+        Head1(@NonNull MarkwonTheme theme) {
+            super(theme, 1);
+        }
+    }
+
+    private static class Head2 extends HeadingSpan {
+        Head2(@NonNull MarkwonTheme theme) {
+            super(theme, 2);
+        }
+    }
+}