overriding the default list handler with an implementation that takes into account the initial starting position

vector/src/main/java/im/vector/app/features/html/EventHtmlRenderer.kt

@@ -152,7 +152,9 @@ class EventHtmlRenderer @Inject constructor(
 class MatrixHtmlPluginConfigure @Inject constructor(private val colorProvider: ColorProvider, private val resources: Resources) : HtmlPlugin.HtmlConfigure {
 
     override fun configureHtml(plugin: HtmlPlugin) {
+
         plugin
+                .addHandler(ListHandlerWithInitialStart())
                 .addHandler(FontTagHandler())
                 .addHandler(ParagraphHandler(DimensionConverter(resources)))
                 .addHandler(MxReplyTagHandler())

vector/src/main/java/im/vector/app/features/html/ListHandlerWithInitialStart.java

@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2022 New Vector Ltd
+ *
+ * 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 im.vector.app.features.html;
+
+import androidx.annotation.NonNull;
+
+import org.commonmark.node.ListItem;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+import io.noties.markwon.MarkwonConfiguration;
+import io.noties.markwon.MarkwonVisitor;
+import io.noties.markwon.RenderProps;
+import io.noties.markwon.SpanFactory;
+import io.noties.markwon.SpannableBuilder;
+import io.noties.markwon.core.CoreProps;
+import io.noties.markwon.html.HtmlTag;
+import io.noties.markwon.html.MarkwonHtmlRenderer;
+import io.noties.markwon.html.TagHandler;
+
+/**
+ * Copied from https://github.com/noties/Markwon/blob/master/markwon-html/src/main/java/io/noties/markwon/html/tag/ListHandler.java#L44
+ * With a modification on the starting list position
+ */
+public class ListHandlerWithInitialStart extends TagHandler {
+
+    private static final String START_KEY = "start";
+
+    @Override
+    public void handle(
+            @NonNull MarkwonVisitor visitor,
+            @NonNull MarkwonHtmlRenderer renderer,
+            @NonNull HtmlTag tag) {
+
+        if (!tag.isBlock()) {
+            return;
+        }
+
+        final HtmlTag.Block block = tag.getAsBlock();
+        final boolean ol = "ol".equals(block.name());
+        final boolean ul = "ul".equals(block.name());
+
+        if (!ol && !ul) {
+            return;
+        }
+
+        final MarkwonConfiguration configuration = visitor.configuration();
+        final RenderProps renderProps = visitor.renderProps();
+        final SpanFactory spanFactory = configuration.spansFactory().get(ListItem.class);
+
+        // Modified line
+        int number = Integer.parseInt(block.attributes().containsKey(START_KEY) ? block.attributes().get(START_KEY) : "1");
+
+        final int bulletLevel = currentBulletListLevel(block);
+
+        for (HtmlTag.Block child : block.children()) {
+
+            visitChildren(visitor, renderer, child);
+
+            if (spanFactory != null && "li".equals(child.name())) {
+
+                // insert list item here
+                if (ol) {
+                    CoreProps.LIST_ITEM_TYPE.set(renderProps, CoreProps.ListItemType.ORDERED);
+                    CoreProps.ORDERED_LIST_ITEM_NUMBER.set(renderProps, number++);
+                } else {
+                    CoreProps.LIST_ITEM_TYPE.set(renderProps, CoreProps.ListItemType.BULLET);
+                    CoreProps.BULLET_LIST_ITEM_LEVEL.set(renderProps, bulletLevel);
+                }
+
+                SpannableBuilder.setSpans(
+                        visitor.builder(),
+                        spanFactory.getSpans(configuration, renderProps),
+                        child.start(),
+                        child.end());
+            }
+        }
+    }
+
+    @NonNull
+    @Override
+    public Collection<String> supportedTags() {
+        return Arrays.asList("ol", "ul");
+    }
+
+    private static int currentBulletListLevel(@NonNull HtmlTag.Block block) {
+        int level = 0;
+        while ((block = block.parent()) != null) {
+            if ("ul".equals(block.name())
+                    || "ol".equals(block.name())) {
+                level += 1;
+            }
+        }
+        return level;
+    }
+}