From 2257a4017ed3bdc4bbf635279d9cd066091a425b Mon Sep 17 00:00:00 2001
From: Michael Daines <mdaines@fastmail.com>
Date: Fri, 13 Jan 2017 12:05:36 -0500
Subject: [PATCH] Create a new instance of Module for every call of Viz. Access
 errors via a new vizLastErrorMessage C API.

---
 Makefile    |  2 +-
 src/post.js | 25 ++++++-------------------
 src/viz.c   | 25 +++++++++----------------
 3 files changed, 16 insertions(+), 36 deletions(-)

diff --git a/Makefile b/Makefile
index 4231702d..fc049149 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,7 @@ viz.js: src/pre.js module.js src/post.js
 	cat $^ > $@
 
 module.js: src/viz.c
-	emcc -v -Os --closure 1 --memory-init-file 0 -s USE_ZLIB=1 -s MODULARIZE=1 -s EXPORTED_FUNCTIONS="['_vizRenderFromString', '_aglasterr', '_dtextract', '_Dtqueue']" -s EXPORTED_RUNTIME_METHODS="['Pointer_stringify', 'ccall', 'UTF8ToString']" -o $@ $< -I$(PREFIX)/include -I$(PREFIX)/include/graphviz -L$(PREFIX)/lib -L$(PREFIX)/lib/graphviz -lgvplugin_core -lgvplugin_dot_layout -lgvplugin_neato_layout -lcdt -lcgraph -lgvc -lgvpr -lpathplan -lexpat -lxdot -lz
+	emcc -v -Os --closure 1 --memory-init-file 0 -s USE_ZLIB=1 -s MODULARIZE=1 -s EXPORTED_FUNCTIONS="['_vizRenderFromString', '_vizLastErrorMessage', '_dtextract', '_Dtqueue']" -s EXPORTED_RUNTIME_METHODS="['Pointer_stringify', 'ccall', 'UTF8ToString']" -o $@ $< -I$(PREFIX)/include -I$(PREFIX)/include/graphviz -L$(PREFIX)/lib -L$(PREFIX)/lib/graphviz -lgvplugin_core -lgvplugin_dot_layout -lgvplugin_neato_layout -lcdt -lcgraph -lgvc -lgvpr -lpathplan -lexpat -lxdot -lz
 
 
 $(PREFIX):
diff --git a/src/post.js b/src/post.js
index b60d307a..88bb6260 100644
--- a/src/post.js
+++ b/src/post.js
@@ -10,27 +10,18 @@
       return render(src, format, engine);
     }
   }
-
-  var graphviz;
-  var errors;
-  
-  function appendError(buf) {
-    errors += graphviz["Pointer_stringify"](buf);
-  }
   
   function render(src, format, engine) {
-    if (typeof graphviz === "undefined") {
-      graphviz = Module();
-    }
-    
-    errors = "";
+    var graphviz = Module();
     
     var resultPointer = graphviz["ccall"]("vizRenderFromString", "number", ["string", "string", "string"], [src, format, engine]);
     var resultString = graphviz["Pointer_stringify"](resultPointer);
-    graphviz["_free"](resultPointer);
+
+    var errorMessagePointer = graphviz["ccall"]("vizLastErrorMessage", "number", [], []);
+    var errorMessageString = graphviz["Pointer_stringify"](errorMessagePointer);
     
-    if (errors != "") {
-      throw errors;
+    if (errorMessageString != "") {
+      throw errorMessageString;
     }
     
     return resultString;
@@ -105,10 +96,6 @@
     }
   }
   
-  Viz.setMemorySize = function(size) {
-    graphviz = Module({ TOTAL_MEMORY: size });
-  }
-  
   Viz.svgXmlToPngBase64 = function(svgXml, scale, callback) {
     Viz.svgXmlToPngImageElement(svgXml, scale, function(err, image) {
       if (err) {
diff --git a/src/viz.c b/src/viz.c
index 3ebf6cda..fe0ff7e5 100644
--- a/src/viz.c
+++ b/src/viz.c
@@ -6,16 +6,20 @@ extern gvplugin_library_t gvplugin_neato_layout_LTX_library;
 extern gvplugin_library_t gvplugin_core_LTX_library;
 
 GVC_t *context = NULL;
+char *errorMessage = NULL;
 
 int vizErrorf(char *buf) {
-  EM_ASM_({ appendError($0); }, buf);
+  errorMessage = buf;
   return 0;
 }
 
-char* vizRenderFromString(const char *src, const char *format, const char *engine) {
+char* vizLastErrorMessage() {
+  return errorMessage;
+}
 
-  Agraph_t *graph;
-  char *result;
+char* vizRenderFromString(const char *src, const char *format, const char *engine) {
+  Agraph_t *graph = NULL;
+  char *result = NULL;
   unsigned int length;
   
   if (context == NULL) {
@@ -28,25 +32,14 @@ char* vizRenderFromString(const char *src, const char *format, const char *engin
   agseterr(AGERR);
   agseterrf(vizErrorf);
   
-  // Reset line numbers.
-  agreadline(1);
-  
   while ((graph = agmemread(src))) {
     if (result == NULL) {
       gvLayout(context, graph, engine);
-      
-      // result is freed in post.js.
       gvRenderData(context, graph, format, &result, &length);
-      
-      gvFreeLayout(context, graph);
     }
     
-    agclose(graph);
-    
-    // agmemread will continue to process graphs from the initial input. Set its *new* input to the empty string so that we don't go into an infinite loop.
     src = "";
   }
-
-  return result;
   
+  return result;
 }