Sanitize latex text placeholder (no new lines)

gradle.properties

@@ -8,7 +8,7 @@ android.enableJetifier=true
 android.enableBuildCache=true
 android.buildCacheDir=build/pre-dex-cache
 
-VERSION_NAME=4.0.1
+VERSION_NAME=4.0.2-SNAPSHOT
 
 GROUP=io.noties.markwon
 POM_DESCRIPTION=Markwon markdown for Android

markwon-ext-latex/build.gradle

@@ -16,8 +16,14 @@ android {
 dependencies {
 
     api project(':markwon-core')
-    api project(':markwon-image')
+
     api deps['jlatexmath-android']
+
+    deps['test'].with {
+        testImplementation it['junit']
+        testImplementation it['robolectric']
+        testImplementation it['mockito']
+    }
 }
 
 registerArtifact(this)

markwon-ext-latex/src/main/java/io/noties/markwon/ext/latex/JLatexMathPlugin.java

@@ -12,6 +12,7 @@ import android.widget.TextView;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.Px;
+import androidx.annotation.VisibleForTesting;
 
 import org.commonmark.parser.Parser;
 
@@ -84,8 +85,8 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
 
         // @since 4.0.0
         private final int paddingHorizontal;
-        // @since 4.0.0
 
+        // @since 4.0.0
         private final int paddingVertical;
 
         // @since 4.0.0
@@ -132,7 +133,10 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
 
                 final int length = visitor.length();
 
-                visitor.builder().append(latex);
+                // @since 4.0.2 we cannot append _raw_ latex as a placeholder-text,
+                // because Android will draw formula for each line of text, thus
+                // leading to formula duplicated (drawn on each line of text)
+                visitor.builder().append(prepareLatexTextPlaceholder(latex));
 
                 final MarkwonConfiguration configuration = visitor.configuration();
 
@@ -161,6 +165,13 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
         AsyncDrawableScheduler.schedule(textView);
     }
 
+    // @since 4.0.2
+    @VisibleForTesting
+    @NonNull
+    static String prepareLatexTextPlaceholder(@NonNull String latex) {
+        return latex.replace('\n', ' ').trim();
+    }
+
     public static class Builder {
 
         private final float textSize;
@@ -350,6 +361,8 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
             final Rect imageBounds = drawable.getResult().getBounds();
             final int canvasWidth = drawable.getLastKnownCanvasWidth();
 
+            // todo: scale down when formula is greater than width (keep ratio and apply height)
+
             if (fitCanvas
                     && imageBounds.width() < canvasWidth) {
                 // we increase only width (keep height as-is)

markwon-ext-latex/src/test/java/io/noties/markwon/ext/latex/JLatexMathPluginTest.java

@@ -0,0 +1,113 @@
+package io.noties.markwon.ext.latex;
+
+import androidx.annotation.NonNull;
+
+import org.commonmark.parser.Parser;
+import org.commonmark.parser.block.BlockParserFactory;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+import java.util.concurrent.ExecutorService;
+
+import io.noties.markwon.MarkwonConfiguration;
+import io.noties.markwon.MarkwonVisitor;
+import io.noties.markwon.SpannableBuilder;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@RunWith(RobolectricTestRunner.class)
+@Config(manifest = Config.NONE)
+public class JLatexMathPluginTest {
+
+    @Test
+    public void latex_text_placeholder() {
+        // text placeholder cannot have new-line characters and should be trimmed from ends
+
+        final String[] in = {
+                "hello",
+                "he\nllo",
+                " hello\n\n",
+                "\n\nhello\n\n",
+                "\n",
+                " \nhello\n "
+        };
+
+        for (String latex : in) {
+            final String placeholder = JLatexMathPlugin.prepareLatexTextPlaceholder(latex);
+            assertTrue(placeholder, placeholder.indexOf('\n') < 0);
+            if (placeholder.length() > 0) {
+                assertFalse(placeholder, Character.isWhitespace(placeholder.charAt(0)));
+                assertFalse(placeholder, Character.isWhitespace(placeholder.charAt(placeholder.length() - 1)));
+            }
+        }
+    }
+
+    @Test
+    public void block_parser_registered() {
+        final JLatexMathPlugin plugin = JLatexMathPlugin.create(0);
+        final Parser.Builder builder = mock(Parser.Builder.class);
+        plugin.configureParser(builder);
+        verify(builder, times(1)).customBlockParserFactory(any(BlockParserFactory.class));
+    }
+
+    @Test
+    public void visitor_registered() {
+        final JLatexMathPlugin plugin = JLatexMathPlugin.create(0);
+        final MarkwonVisitor.Builder builder = mock(MarkwonVisitor.Builder.class);
+        plugin.configureVisitor(builder);
+        //noinspection unchecked
+        verify(builder, times(1))
+                .on(eq(JLatexMathBlock.class), any(MarkwonVisitor.NodeVisitor.class));
+    }
+
+    @Test
+    public void visit() {
+        final JLatexMathPlugin plugin = JLatexMathPlugin.create(0, new JLatexMathPlugin.BuilderConfigure() {
+            @Override
+            public void configureBuilder(@NonNull JLatexMathPlugin.Builder builder) {
+                // no async in test (nooped for this test)
+                builder.executorService(mock(ExecutorService.class));
+            }
+        });
+        final MarkwonVisitor.Builder builder = mock(MarkwonVisitor.Builder.class);
+        final ArgumentCaptor<MarkwonVisitor.NodeVisitor> captor =
+                ArgumentCaptor.forClass(MarkwonVisitor.NodeVisitor.class);
+        plugin.configureVisitor(builder);
+        //noinspection unchecked
+        verify(builder, times(1))
+                .on(eq(JLatexMathBlock.class), captor.capture());
+        final MarkwonVisitor.NodeVisitor nodeVisitor = captor.getValue();
+
+        final MarkwonVisitor visitor = mock(MarkwonVisitor.class);
+        final JLatexMathBlock block = mock(JLatexMathBlock.class);
+        when(block.latex()).thenReturn(" first\nsecond\n ");
+
+        final SpannableBuilder spannableBuilder = mock(SpannableBuilder.class);
+        when(visitor.builder()).thenReturn(spannableBuilder);
+        when(visitor.configuration()).thenReturn(mock(MarkwonConfiguration.class));
+
+        //noinspection unchecked
+        nodeVisitor.visit(visitor, block);
+
+        verify(block, times(1)).latex();
+        verify(visitor, times(1)).length();
+
+        final ArgumentCaptor<String> stringArgumentCaptor = ArgumentCaptor.forClass(String.class);
+        verify(spannableBuilder, times(1)).append(stringArgumentCaptor.capture());
+
+        final String placeholder = stringArgumentCaptor.getValue();
+        assertTrue(placeholder, placeholder.indexOf('\n') < 0);
+
+        verify(visitor, times(1)).setSpans(eq(0), any());
+    }
+}

sample/src/main/java/io/noties/markwon/sample/latex/LatexActivity.java

@@ -68,20 +68,23 @@ public class LatexActivity extends Activity {
                 .build();
 
         if (true) {
-            final String l = "$$\n" +
+//            final String l = "$$\n" +
-                    "  P(X=r)=\\frac{\\lambda^r e^{-\\lambda}}{r!}\n" +
+//                    "  P(X=r)=\\frac{\\lambda^r e^{-\\lambda}}{r!}\n" +
-                    "$$\n" +
+//                    "$$\n" +
-                    "\n" +
+//                    "\n" +
-                    "$$\n" +
+//                    "$$\n" +
-                    "  P(X<r)=P(X<r-1)\n" +
+//                    "  P(X<r)=P(X<r-1)\n" +
-                    "$$\n" +
+//                    "$$\n" +
-                    "\n" +
+//                    "\n" +
-                    "$$\n" +
+//                    "$$\n" +
-                    "  P(X>r)=1-P(X<r=1)\n" +
+//                    "  P(X>r)=1-P(X<r=1)\n" +
-                    "$$\n" +
+//                    "$$\n" +
-                    "\n" +
+//                    "\n" +
-                    "$$\n" +
+//                    "$$\n" +
-                    "  \\text{Variance} = \\lambda\n" +
+//                    "  \\text{Variance} = \\lambda\n" +
+//                    "$$";
+            final String l = "$$ \n" +
+                    "    \\sigma_T^2 = \\frac{1-p}{p^2}\n" +
                     "$$";
             markwon.setMarkdown(textView, l);
             return;