Replaced custom SpannableBuilder with ReverseSpannableStringBuilder

Background:
The usage and maintaining of SpannableBuilder is reduced by using
a good-old-SpannableStringBuilder directly but making sure its spans are
reversed.

The implementation is credited Uncodin/bypass

library/src/main/java/ru/noties/markwon/ReverseSpannableStringBuilder.java

@@ -0,0 +1,42 @@
+package ru.noties.markwon;
+
+import android.text.SpannableStringBuilder;
+
+/**
+ * Copied as is from @see <a href = "https://github.com/Uncodin/bypass/blob/master/platform/android/
+ * library/src/in/uncod/android/bypass/ReverseSpannableStringBuilder.java">Uncodin/bypass</a>
+ */
+public class ReverseSpannableStringBuilder extends SpannableStringBuilder {
+
+    public ReverseSpannableStringBuilder() {
+        super();
+    }
+
+    public ReverseSpannableStringBuilder(CharSequence text, int start, int end) {
+        super(text, start, end);
+    }
+
+    @Override
+    public <T> T[] getSpans(int queryStart, int queryEnd, Class<T> kind) {
+        T[] ret = super.getSpans(queryStart, queryEnd, kind);
+        reverse(ret);
+        return ret;
+    }
+
+    private static void reverse(Object[] arr) {
+        if (arr == null) {
+            return;
+        }
+
+        int i = 0;
+        int j = arr.length - 1;
+        Object tmp;
+        while (j > i) {
+            tmp = arr[j];
+            arr[j] = arr[i];
+            arr[i] = tmp;
+            j--;
+            i++;
+        }
+    }
+}

library/src/main/java/ru/noties/markwon/SpannableBuilder.java

@@ -1,241 +0,0 @@
-package ru.noties.markwon;
-
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.text.SpannableStringBuilder;
-import android.text.Spanned;
-
-import java.util.ArrayDeque;
-import java.util.Deque;
-import java.util.Iterator;
-
-/**
- * This class is used to _revert_ order of applied spans. Original SpannableStringBuilder
- * is using an array to store all the information about spans. So, a span that is added first
- * will be drawn first, which leads to subtle bugs (spans receive wrong `x` values when
- * requested to draw itself)
- *
- * @since 1.0.1
- */
-@SuppressWarnings({"WeakerAccess", "unused"})
-public class SpannableBuilder {
-
-    // do not implement CharSequence (or any of Spanned interfaces)
-
-    // we will be using SpannableStringBuilder anyway as a backing store
-    // as it has tight connection with system (implements some hidden methods, etc)
-    private final SpannableStringBuilder builder;
-
-    // actually we might be just using ArrayList
-    private final Deque<Span> spans = new ArrayDeque<>(8);
-
-    public SpannableBuilder() {
-        this("");
-    }
-
-    public SpannableBuilder(@NonNull CharSequence cs) {
-        this.builder = new SpannableStringBuilderImpl(cs.toString());
-        copySpans(0, cs);
-    }
-
-    /**
-     * Additional method that takes a String, which is proven to NOT contain any spans
-     *
-     * @param text String to append
-     * @return this instance
-     */
-    @NonNull
-    public SpannableBuilder append(@NonNull String text) {
-        builder.append(text);
-        return this;
-    }
-
-    @NonNull
-    public SpannableBuilder append(char c) {
-        builder.append(c);
-        return this;
-    }
-
-    @NonNull
-    public SpannableBuilder append(@NonNull CharSequence cs) {
-
-        copySpans(length(), cs);
-
-        builder.append(cs.toString());
-
-        return this;
-    }
-
-    @NonNull
-    public SpannableBuilder append(@NonNull CharSequence cs, @NonNull Object span) {
-        final int length = length();
-        append(cs);
-        setSpan(span, length);
-        return this;
-    }
-
-    @NonNull
-    public SpannableBuilder append(@NonNull CharSequence cs, @NonNull Object span, int flags) {
-        final int length = length();
-        append(cs);
-        setSpan(span, length, length(), flags);
-        return this;
-    }
-
-    @NonNull
-    public SpannableBuilder setSpan(@NonNull Object span, int start) {
-        return setSpan(span, start, length());
-    }
-
-    @NonNull
-    public SpannableBuilder setSpan(@NonNull Object span, int start, int end) {
-        return setSpan(span, start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-    }
-
-    @NonNull
-    public SpannableBuilder setSpan(@NonNull Object span, int start, int end, int flags) {
-        spans.push(new Span(span, start, end, flags));
-        return this;
-    }
-
-    public int length() {
-        return builder.length();
-    }
-
-    public char charAt(int index) {
-        return builder.charAt(index);
-    }
-
-    public char lastChar() {
-        return builder.charAt(length() - 1);
-    }
-
-    @NonNull
-    public CharSequence removeFromEnd(int start) {
-
-        // this method is not intended to be used by clients
-        // it's a workaround to support tables
-
-        final int end = length();
-
-        // as we do not expose builder and do no apply spans to it, we are safe to NOT to convert to String
-        final SpannableStringBuilderImpl impl = new SpannableStringBuilderImpl(builder.subSequence(start, end));
-
-        final Iterator<Span> iterator = spans.iterator();
-
-        Span span;
-
-        while (iterator.hasNext() && ((span = iterator.next())) != null) {
-            if (span.start >= start && span.end <= end) {
-                impl.setSpan(span.what, span.start - start, span.end - start, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-                iterator.remove();
-            }
-        }
-
-        builder.replace(start, end, "");
-
-        return impl;
-    }
-
-    @Override
-    @NonNull
-    public String toString() {
-        return builder.toString();
-    }
-
-    @NonNull
-    public CharSequence text() {
-
-        // okay, in order to not allow external modification and keep our spans order
-        // we should not return our builder
-        //
-        // plus, if this method was called -> all spans would be applied, which potentially
-        // breaks the order that we intend to use
-        // so, we will defensively copy builder
-
-        // as we do not expose builder and do no apply spans to it, we are safe to NOT to convert to String
-        final SpannableStringBuilderImpl impl = new SpannableStringBuilderImpl(builder);
-
-        for (Span span : spans) {
-            impl.setSpan(span.what, span.start, span.end, span.flags);
-        }
-
-        // now, let's remove trailing newLines (so small amounts of text are displayed correctly)
-        // @since 1.0.2
-
-        final int length = impl.length();
-        if (length > 0) {
-            int amount = 0;
-            for (int i = length - 1; i >= 0; i--) {
-                if (Character.isWhitespace(impl.charAt(i))) {
-                    amount += 1;
-                } else {
-                    break;
-                }
-            }
-            if (amount > 0) {
-                impl.replace(length - amount, length, "");
-            }
-        }
-
-        return impl;
-    }
-
-    private void copySpans(final int index, @Nullable CharSequence cs) {
-
-        // we must identify already reversed Spanned...
-        // and (!) iterate backwards when adding (to preserve order)
-
-        if (cs instanceof Spanned) {
-
-            final Spanned spanned = (Spanned) cs;
-            final boolean reverse = spanned instanceof SpannedReversed;
-
-            final Object[] spans = spanned.getSpans(0, spanned.length(), Object.class);
-            final int length = spans != null
-                    ? spans.length
-                    : 0;
-
-            if (length > 0) {
-                if (reverse) {
-                    Object o;
-                    for (int i = length - 1; i >= 0; i--) {
-                        o = spans[i];
-                        setSpan(
-                                o,
-                                index + spanned.getSpanStart(o),
-                                index + spanned.getSpanEnd(o),
-                                spanned.getSpanFlags(o)
-                        );
-                    }
-                } else {
-                    Object o;
-                    for (int i = 0; i < length; i++) {
-                        o = spans[i];
-                        setSpan(
-                                o,
-                                index + spanned.getSpanStart(o),
-                                index + spanned.getSpanEnd(o),
-                                spanned.getSpanFlags(o)
-                        );
-                    }
-                }
-            }
-        }
-    }
-
-    static class Span {
-
-        final Object what;
-        int start;
-        int end;
-        final int flags;
-
-        Span(@NonNull Object what, int start, int end, int flags) {
-            this.what = what;
-            this.start = start;
-            this.end = end;
-            this.flags = flags;
-        }
-    }
-}

library/src/main/java/ru/noties/markwon/SpannableStringBuilderImpl.java

@@ -1,13 +0,0 @@
-package ru.noties.markwon;
-
-import android.text.SpannableStringBuilder;
-
-/**
- * @since 1.0.1
- */
-class SpannableStringBuilderImpl extends SpannableStringBuilder implements SpannedReversed {
-
-    SpannableStringBuilderImpl(CharSequence text) {
-        super(text);
-    }
-}

library/src/main/java/ru/noties/markwon/SpannedReversed.java

@@ -1,9 +0,0 @@
-package ru.noties.markwon;
-
-import android.text.Spanned;
-
-/**
- * @since 1.0.1
- */
-interface SpannedReversed extends Spanned {
-}

library/src/main/java/ru/noties/markwon/renderer/SpannableMarkdownVisitor.java

@@ -2,6 +2,7 @@ package ru.noties.markwon.renderer;
 
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
+import android.text.SpannableStringBuilder;
 import android.text.Spanned;
 import android.text.TextUtils;
 
@@ -39,7 +40,7 @@ import java.util.ArrayList;
 import java.util.Deque;
 import java.util.List;
 
-import ru.noties.markwon.SpannableBuilder;
+import ru.noties.markwon.ReverseSpannableStringBuilder;
 import ru.noties.markwon.SpannableConfiguration;
 import ru.noties.markwon.SpannableFactory;
 import ru.noties.markwon.renderer.html.SpannableHtmlParser;
@@ -52,7 +53,7 @@ import ru.noties.markwon.tasklist.TaskListItem;
 public class SpannableMarkdownVisitor extends AbstractVisitor {
 
     private final SpannableConfiguration configuration;
-    private final SpannableBuilder builder;
+    private final SpannableStringBuilder builder;
     private final Deque<HtmlInlineItem> htmlInlineItems;
 
     private final SpannableTheme theme;
@@ -67,7 +68,7 @@ public class SpannableMarkdownVisitor extends AbstractVisitor {
 
     public SpannableMarkdownVisitor(
             @NonNull SpannableConfiguration configuration,
-            @NonNull SpannableBuilder builder
+            @NonNull SpannableStringBuilder builder
     ) {
         this.configuration = configuration;
         this.builder = builder;
@@ -363,10 +364,9 @@ public class SpannableMarkdownVisitor extends AbstractVisitor {
             if (pendingTableRow == null) {
                 pendingTableRow = new ArrayList<>(2);
             }
-
             pendingTableRow.add(new TableRowSpan.Cell(
                     tableCellAlignment(cell.getAlignment()),
-                    builder.removeFromEnd(length)
+                    removeFromEnd(length)
             ));
 
             tableRowIsHeader = cell.isHeader();
@@ -378,6 +378,22 @@ public class SpannableMarkdownVisitor extends AbstractVisitor {
         return handled;
     }
 
+    @NonNull
+    private CharSequence removeFromEnd(int start) {
+
+        // this method is not intended to be used by clients
+        // it's a workaround to support tables
+
+        final int end = builder.length();
+
+        // as we do not expose builder and do no apply spans to it, we are safe to NOT to convert to String
+        final SpannableStringBuilder impl = new ReverseSpannableStringBuilder(builder, start, end);
+        builder.delete(start, end);
+
+        return impl;
+    }
+
+
     @Override
     public void visit(Paragraph paragraph) {
         final boolean inTightList = isInTightList(paragraph);
@@ -504,7 +520,7 @@ public class SpannableMarkdownVisitor extends AbstractVisitor {
 
     private void newLine() {
         if (builder.length() > 0
-                && '\n' != builder.lastChar()) {
+                && '\n' != builder.charAt(builder.length() - 1)) {
             builder.append('\n');
         }
     }

library/src/main/java/ru/noties/markwon/renderer/SpannableRenderer.java

@@ -1,18 +1,19 @@
 package ru.noties.markwon.renderer;
 
 import android.support.annotation.NonNull;
+import android.text.SpannableStringBuilder;
 
 import org.commonmark.node.Node;
 
-import ru.noties.markwon.SpannableBuilder;
+import ru.noties.markwon.ReverseSpannableStringBuilder;
 import ru.noties.markwon.SpannableConfiguration;
 
 public class SpannableRenderer {
 
     @NonNull
     public CharSequence render(@NonNull SpannableConfiguration configuration, @NonNull Node node) {
-        final SpannableBuilder builder = new SpannableBuilder();
+        final SpannableStringBuilder builder = new ReverseSpannableStringBuilder();
         node.accept(new SpannableMarkdownVisitor(configuration, builder));
-        return builder.text();
+        return builder;
     }
 }

sample-custom-extension/src/main/java/ru/noties/markwon/sample/extension/IconVisitor.java

@@ -1,25 +1,25 @@
 package ru.noties.markwon.sample.extension;
 
 import android.support.annotation.NonNull;
+import android.text.SpannableStringBuilder;
+import android.text.Spanned;
 import android.text.TextUtils;
-import android.widget.TextView;
 
 import org.commonmark.node.CustomNode;
 
-import ru.noties.markwon.SpannableBuilder;
 import ru.noties.markwon.SpannableConfiguration;
 import ru.noties.markwon.renderer.SpannableMarkdownVisitor;
 
 @SuppressWarnings("WeakerAccess")
 public class IconVisitor extends SpannableMarkdownVisitor {
 
-    private final SpannableBuilder builder;
+    private final SpannableStringBuilder builder;
 
     private final IconSpanProvider iconSpanProvider;
 
     public IconVisitor(
             @NonNull SpannableConfiguration configuration,
-            @NonNull SpannableBuilder builder,
+            @NonNull SpannableStringBuilder builder,
             @NonNull IconSpanProvider iconSpanProvider
     ) {
         super(configuration, builder);
@@ -51,7 +51,7 @@ public class IconVisitor extends SpannableMarkdownVisitor {
                 final int length = builder.length();
 
                 builder.append(name);
-                builder.setSpan(iconSpanProvider.provide(name, color, size), length);
+                builder.setSpan(iconSpanProvider.provide(name, color, size), length, length, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
                 builder.append(' ');
                 
                 return true;

sample-custom-extension/src/main/java/ru/noties/markwon/sample/extension/MainActivity.java

@@ -3,6 +3,7 @@ package ru.noties.markwon.sample.extension;
 import android.app.Activity;
 import android.graphics.Typeface;
 import android.os.Bundle;
+import android.text.SpannableStringBuilder;
 import android.widget.TextView;
 
 import org.commonmark.ext.gfm.strikethrough.StrikethroughExtension;
@@ -12,7 +13,7 @@ import org.commonmark.parser.Parser;
 
 import java.util.Arrays;
 
-import ru.noties.markwon.SpannableBuilder;
+import ru.noties.markwon.ReverseSpannableStringBuilder;
 import ru.noties.markwon.SpannableConfiguration;
 import ru.noties.markwon.spans.SpannableTheme;
 import ru.noties.markwon.tasklist.TaskListExtension;
@@ -45,7 +46,7 @@ public class MainActivity extends Activity {
 
         final Node node = parser.parse(markdown);
 
-        final SpannableBuilder builder = new SpannableBuilder();
+        final SpannableStringBuilder builder = new ReverseSpannableStringBuilder();
 
         // please note that here I am passing `0` as fallback it means that if markdown references
         // unknown icon, it will try to load fallback one and will fail with ResourceNotFound. It's
@@ -70,6 +71,6 @@ public class MainActivity extends Activity {
         node.accept(visitor);
 
         // apply
-        textView.setText(builder.text());
+        textView.setText(builder);
     }
 }