Improve local PlantUML error reporting

Author: beNative

electron/main.ts

@@ -483,11 +483,11 @@ ipcMain.handle('plantuml:render-svg', async (_, diagram: string, format: 'svg' =
                     return;
                 }
 
-                const exitDetails = errorOutput.trim() || `Renderer exited with code ${code}.`;
+                const exitDetails = errorOutput.trim();
                 finalize({
                     success: false,
-                    error: 'Local PlantUML renderer failed to produce output.',
-                    details: exitDetails,
+                    error: derivePlantumlFriendlyError(exitDetails, code ?? undefined),
+                    details: exitDetails || (typeof code === 'number' ? `Renderer exited with code ${code}.` : undefined),
                 });
             });
 
@@ -514,6 +514,38 @@ let plantumlJarLookupPromise: Promise<string> | null = null;
 
 const PLANTUML_JAR_RELATIVE_PATH = path.join('assets', 'plantuml', 'plantuml.jar');
 
+function derivePlantumlFriendlyError(details?: string | null, exitCode?: number): string {
+    if (details) {
+        const normalized = details.toLowerCase();
+
+        if (normalized.includes('cannot run program') && normalized.includes('"dot"')) {
+            return 'Graphviz (the "dot" executable) is required for the local PlantUML renderer. Install Graphviz or add it to your PATH.';
+        }
+
+        if (normalized.includes('graphviz') && normalized.includes('not found')) {
+            return 'Graphviz binaries were not found. Install Graphviz to enable the local PlantUML renderer.';
+        }
+
+        if (normalized.includes('unsupportedclassversionerror')) {
+            return 'The bundled PlantUML renderer requires a newer Java runtime. Update Java and try again.';
+        }
+
+        if (normalized.includes('could not find or load main class') || normalized.includes('classnotfoundexception')) {
+            return 'The PlantUML renderer could not start. Ensure assets/plantuml/plantuml.jar is present and accessible.';
+        }
+
+        if (normalized.includes('permission denied')) {
+            return 'The PlantUML renderer could not be executed because of missing file permissions.';
+        }
+    }
+
+    if (typeof exitCode === 'number' && exitCode !== 0) {
+        return `Local PlantUML renderer exited with code ${exitCode}.`;
+    }
+
+    return 'Local PlantUML renderer failed to produce output.';
+}
+
 async function resolvePlantUmlJar(): Promise<string> {
     if (cachedPlantumlJarPath) {
         return cachedPlantumlJarPath;

services/preview/markdownRenderer.tsx

@@ -621,6 +621,7 @@ const MarkdownViewer = forwardRef<HTMLDivElement, MarkdownViewerProps>(({ conten
           gap: 0.5rem;
           align-items: flex-start;
           text-align: left;
+          user-select: text;
         }
 
         .df-mermaid-error__message,
@@ -636,6 +637,7 @@ const MarkdownViewer = forwardRef<HTMLDivElement, MarkdownViewerProps>(({ conten
           padding: 0.75rem 0.85rem;
           background: rgba(var(--color-background), 0.6);
           color: rgba(var(--color-text-secondary), 0.95);
+          user-select: text;
         }
 
         .df-mermaid-error__details > summary,

services/preview/plantumlDiagram.tsx

@@ -15,9 +15,21 @@ interface PlantUMLErrorProps {
   details?: string | null;
 }
 
+const stopPointerEvent = (event: React.SyntheticEvent) => {
+  event.stopPropagation();
+};
+
 const PlantUMLError: React.FC<PlantUMLErrorProps> = ({ message, details }) => (
   <div className="df-plantuml" role="alert">
-    <div className="df-plantuml-error">
+    <div
+      className="df-plantuml-error"
+      onPointerDown={stopPointerEvent}
+      onPointerMove={stopPointerEvent}
+      onPointerUp={stopPointerEvent}
+      onDoubleClick={stopPointerEvent}
+      onClick={stopPointerEvent}
+      onWheel={stopPointerEvent}
+    >
       <div className="df-plantuml-error__message">{message}</div>
       {details && details.trim() && (
         <details className="df-plantuml-error__details">

services/preview/plantumlRenderer.tsx

@@ -73,10 +73,12 @@ const PlantUMLPreview: React.FC<PlantUMLPreviewProps> = ({ content, settings })
           gap: 0.5rem;
           align-items: flex-start;
           text-align: left;
+          user-select: text;
         }
 
         .df-plantuml-error__details {
           font-size: 0.85rem;
+          user-select: text;
         }
       `}</style>
     </ZoomPanContainer>