JLatexMathPlugin add error handling

CHANGELOG.md

@@ -13,8 +13,12 @@
   ```
 * `JLatexMathPlugin`: add `theme` (to customize both inlines and blocks)
 * `JLatexMathPlugin`: add `renderMode` to use previous (pre `4.3.0`) LaTeX rendering
+* add `JLatexMathPlugin.ErrorHandler` to catch latex rendering errors and (optionally) display error drawable ([#204])
 * add `SoftBreakAddsNewLinePlugin` plugin (`core` module)
-* `LinkResolverDef` defaults to `https` when a link does not have scheme information
+* `LinkResolverDef` defaults to `https` when a link does not have scheme information ([#75])
+
+[#75]: https://github.com/noties/Markwon/issues/75
+[#204]: https://github.com/noties/Markwon/issues/204 
 
 
 # 4.2.2

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

@@ -29,6 +29,7 @@ import io.noties.markwon.image.AsyncDrawable;
 import io.noties.markwon.image.AsyncDrawableLoader;
 import io.noties.markwon.image.AsyncDrawableScheduler;
 import io.noties.markwon.image.AsyncDrawableSpan;
+import io.noties.markwon.image.DrawableUtils;
 import io.noties.markwon.image.ImageSizeResolver;
 import io.noties.markwon.inlineparser.MarkwonInlineParserPlugin;
 import ru.noties.jlatexmath.JLatexMathDrawable;
@@ -62,6 +63,22 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
         BLOCKS_AND_INLINES
     }
 
+    /**
+     * @since 4.3.0-SNAPSHOT
+     */
+    public interface ErrorHandler {
+
+        /**
+         * @param latex that caused the error or null if operated `AsyncDrawable`
+         *              is not an instance of `JLatexAsyncDrawable`
+         * @param error occurred
+         * @return (optional) error drawable that will be used instead (if drawable will have bounds
+         * it will be used, if not intrinsic bounds will be set)
+         */
+        @Nullable
+        Drawable handleError(@Nullable String latex, @NonNull Throwable error);
+    }
+
     public interface BuilderConfigure {
         void configureBuilder(@NonNull Builder builder);
     }
@@ -125,11 +142,15 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
         // @since 4.3.0-SNAPSHOT
         private final RenderMode renderMode;
 
+        // @since 4.3.0-SNAPSHOT
+        private final ErrorHandler errorHandler;
+
         private final ExecutorService executorService;
 
         Config(@NonNull Builder builder) {
             this.theme = builder.theme.build();
             this.renderMode = builder.renderMode;
+            this.errorHandler = builder.errorHandler;
             // @since 4.0.0
             ExecutorService executorService = builder.executorService;
             if (executorService == null) {
@@ -284,6 +305,9 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
         // @since 4.3.0-SNAPSHOT
         private RenderMode renderMode = RenderMode.BLOCKS_AND_INLINES;
 
+        // @since 4.3.0-SNAPSHOT
+        private ErrorHandler errorHandler;
+
         // @since 4.0.0
         private ExecutorService executorService;
 
@@ -305,6 +329,12 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
             return this;
         }
 
+        @NonNull
+        public Builder errorHandler(@Nullable ErrorHandler errorHandler) {
+            this.errorHandler = errorHandler;
+            return this;
+        }
+
         /**
          * @since 4.0.0
          */
@@ -351,10 +381,24 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
                         try {
                             execute();
                         } catch (Throwable t) {
+                            // @since 4.3.0-SNAPSHOT add error handling
+                            final ErrorHandler errorHandler = config.errorHandler;
+                            if (errorHandler == null) {
+                                // as before
                                 Log.e(
                                         "JLatexMathPlugin",
                                         "Error displaying latex: `" + drawable.getDestination() + "`",
                                         t);
+                            } else {
+                                final Drawable errorDrawable = errorHandler.handleError(
+                                        drawable.getDestination(),
+                                        t
+                                );
+                                if (errorDrawable != null) {
+                                    DrawableUtils.applyIntrinsicBoundsIfEmpty(errorDrawable);
+                                    setResult(drawable, errorDrawable);
+                                }
+                            }
                         }
                     }
 
@@ -370,19 +414,7 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
                             jLatexMathDrawable = createInlineDrawable(jLatextAsyncDrawable.getDestination());
                         }
 
-                        // we must post to handler, but also have a way to identify the drawable
+                        setResult(drawable, jLatexMathDrawable);
-                        // for which we are posting (in case of cancellation)
-                        handler.postAtTime(new Runnable() {
-                            @Override
-                            public void run() {
-                                // remove entry from cache (it will be present if task is not cancelled)
-                                if (cache.remove(drawable) != null
-                                        && drawable.isAttached()) {
-                                    drawable.setResult(jLatexMathDrawable);
-                                }
-
-                            }
-                        }, drawable, SystemClock.uptimeMillis());
                     }
                 }));
             }
@@ -456,6 +488,23 @@ public class JLatexMathPlugin extends AbstractMarkwonPlugin {
 
             return builder.build();
         }
+
+        // @since 4.3.0-SNAPSHOT
+        private void setResult(@NonNull final AsyncDrawable drawable, @NonNull final Drawable result) {
+            // we must post to handler, but also have a way to identify the drawable
+            // for which we are posting (in case of cancellation)
+            handler.postAtTime(new Runnable() {
+                @Override
+                public void run() {
+                    // remove entry from cache (it will be present if task is not cancelled)
+                    if (cache.remove(drawable) != null
+                            && drawable.isAttached()) {
+                        drawable.setResult(result);
+                    }
+
+                }
+            }, drawable, SystemClock.uptimeMillis());
+        }
     }
 
     private static class InlineImageSizeResolver extends ImageSizeResolver {

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

@@ -2,12 +2,15 @@ package io.noties.markwon.sample.latex;
 
 import android.content.res.Resources;
 import android.graphics.drawable.ColorDrawable;
+import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.widget.TextView;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.core.content.ContextCompat;
 
+import io.noties.debug.Debug;
 import io.noties.markwon.Markwon;
 import io.noties.markwon.ext.latex.JLatexMathPlugin;
 import io.noties.markwon.ext.latex.JLatexMathTheme;
@@ -57,6 +60,7 @@ public class LatexActivity extends ActivityWithMenuOptions {
                 .add("bangle", this::bangle)
                 .add("boxes", this::boxes)
                 .add("insideBlockQuote", this::insideBlockQuote)
+                .add("error", this::error)
                 .add("legacy", this::legacy);
     }
 
@@ -95,6 +99,27 @@ public class LatexActivity extends ActivityWithMenuOptions {
         render(md);
     }
 
+    private void error() {
+        final String md = wrapLatexInSampleMarkdown("\\sum_{i=0}^\\infty x \\cdot 0 \\rightarrow \\iMightNotExist{0}");
+
+        final Markwon markwon = Markwon.builder(this)
+                .usePlugin(MarkwonInlineParserPlugin.create())
+                .usePlugin(JLatexMathPlugin.create(textView.getTextSize(), builder -> {
+                    //noinspection Convert2Lambda
+                    builder.errorHandler(new JLatexMathPlugin.ErrorHandler() {
+                        @Nullable
+                        @Override
+                        public Drawable handleError(@Nullable String latex, @NonNull Throwable error) {
+                            Debug.e(error, latex);
+                            return ContextCompat.getDrawable(LatexActivity.this, R.drawable.ic_android_black_24dp);
+                        }
+                    });
+                }))
+                .build();
+
+        markwon.setMarkdown(textView, md);
+    }
+
     private void legacy() {
         final String md = wrapLatexInSampleMarkdown(LATEX_BANGLE);