Add custom TagHandler for <code> tags to add monospace typeface

app/src/main/java/io/github/hidroh/materialistic/AppUtils.java

@@ -92,6 +92,7 @@ public class AppUtils {
     public static final int HOT_FACTOR = 3;
     private static final String HOST_ITEM = "item";
     private static final String HOST_USER = "user";
+    private static final HtmlCodeTagHandler CODE_TAG_HANDLER = new HtmlCodeTagHandler();
 
     public static void openWebUrlExternal(Context context, @Nullable WebItem item,
                                           String url, @Nullable CustomTabsSession session) {
@@ -184,14 +185,16 @@ public static CharSequence fromHtml(String htmlText, boolean compact) {
         if (TextUtils.isEmpty(htmlText)) {
             return null;
         }
-        CharSequence spanned;
+        final CharSequence spanned;
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
             //noinspection InlinedApi
             spanned = Html.fromHtml(htmlText, compact ?
-                    Html.FROM_HTML_MODE_COMPACT : Html.FROM_HTML_MODE_LEGACY);
+                    Html.FROM_HTML_MODE_COMPACT : Html.FROM_HTML_MODE_LEGACY,
+                    null,
+                    CODE_TAG_HANDLER);
         } else {
             //noinspection deprecation
-            spanned = Html.fromHtml(htmlText);
+            spanned = Html.fromHtml(htmlText, null, CODE_TAG_HANDLER);
         }
         return trim(spanned);
     }

app/src/main/java/io/github/hidroh/materialistic/HtmlCodeTagHandler.java

@@ -0,0 +1,71 @@
+package io.github.hidroh.materialistic;
+
+import android.text.Editable;
+import android.text.Html;
+import android.text.Spannable;
+import android.text.Spanned;
+import android.text.style.TypefaceSpan;
+
+import org.xml.sax.XMLReader;
+
+/**
+ * TagHandler that 'knows' how to handle <code>code<code> tags.
+ * This handler can be used in the Html.fromHtml method to support formatting of code tags using the monospace typeface.
+ *
+ * Hackernews returns <code>&lt;pre&gt;&lt;code&gt;</code> blocks, but we are only interested in the inner code.
+ * The pre tag is then ignored by the Html.fromHtml default tag handler.
+ */
+public class HtmlCodeTagHandler implements Html.TagHandler {
+    @Override
+    public void handleTag(boolean opening, String tag, Editable output, XMLReader xmlReader) {
+        if (tag.equalsIgnoreCase("code")) {
+            if (opening) {
+                start(output, new Monospace());
+            } else {
+                end(output, Monospace.class, new TypefaceSpan("monospace"));
+            }
+        }
+    }
+
+    // This is copied from android.text.HtmlToSpannedConverter#start
+    private static void start(Editable text, Object mark) {
+        int len = text.length();
+        text.setSpan(mark, len, len, Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
+    }
+
+    // This is copied from android.text.HtmlToSpannedConverter#end
+    private static void end(Editable text, Class kind, Object repl) {
+        Object obj = getLast(text, kind);
+        if (obj != null) {
+            setSpanFromMark(text, obj, repl);
+        }
+    }
+
+    // This is copied from android.text.HtmlToSpannedConverter#setSpanFromMark
+    private static void setSpanFromMark(Spannable text, Object mark, Object... spans) {
+        int where = text.getSpanStart(mark);
+        text.removeSpan(mark);
+        int len = text.length();
+        if (where != len) {
+            for (Object span : spans) {
+                text.setSpan(span, where, len, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+            }
+        }
+    }
+
+    // This is copied from android.text.HtmlToSpannedConverter#getLast
+    private static <T> T getLast(Spanned text, Class<T> kind) {
+        /*
+         * This knows that the last returned object from getSpans()
+         * will be the most recently added.
+         */
+        T[] objs = text.getSpans(0, text.length(), kind);
+        if (objs.length == 0) {
+            return null;
+        } else {
+            return objs[objs.length - 1];
+        }
+    }
+    // This is copied from android.text.HtmlToSpannedConverter.Monospace
+    private static class Monospace {}
+}

app/src/test/java/io/github/hidroh/materialistic/AppUtilsTest.java

@@ -10,7 +10,9 @@
 import android.support.design.widget.AppBarLayout;
 import android.support.design.widget.FloatingActionButton;
 import android.support.v4.content.LocalBroadcastManager;
+import android.text.SpannedString;
 import android.text.format.DateUtils;
+import android.text.style.TypefaceSpan;
 import android.view.ContextThemeWrapper;
 import android.view.MotionEvent;
 import android.view.View;
@@ -239,6 +241,30 @@ public void testTrimHtmlWhitespaces() {
         assertThat(textView).hasTextString("paragraph");
     }
 
+    @Test
+    public void testPreformattedTextHasMonospaceTypeface() {
+        TextView textView = new TextView(context);
+        textView.setText(AppUtils.fromHtml("<pre><code>val x = myCode()</code></pre>"));
+        assertThat(textView).hasTextString("val x = myCode()");
+
+        SpannedString view = (SpannedString) textView.getText();
+        TypefaceSpan[] spans = view.getSpans(0, view.length(), TypefaceSpan.class);
+        assertThat(spans.length).isEqualTo(1);
+        assertThat(spans[0].getFamily()).isEqualTo("monospace");
+    }
+
+    @Test
+    public void testPreformattedTextHasMultipleMonospaceTypeface() {
+        TextView textView = new TextView(context);
+        textView.setText(AppUtils.fromHtml("<pre><code>val x = myCode()</code></pre><p>some more text<br/></p><pre><code>val y = myCode()</code></pre><p>And more text"));
+
+        SpannedString view = (SpannedString) textView.getText();
+        TypefaceSpan[] spans = view.getSpans(0, view.length(), TypefaceSpan.class);
+        assertThat(spans.length).isEqualTo(2);
+        assertThat(spans[0].getFamily()).isEqualTo("monospace");
+        assertThat(spans[1].getFamily()).isEqualTo("monospace");
+    }
+
     @Test
     public void testOpenExternalUrlNoConnection() {
         shadowOf((ConnectivityManager) context