From 8204bbefa86361eb5d25055e3ed28d520237ee06 Mon Sep 17 00:00:00 2001
From: Tj Holowaychuk <tj@vision-media.ca>
Date: Wed, 27 Oct 2010 11:10:30 -0700
Subject: [PATCH 1/3] Added Canvas::Error()

---
 src/canvas.cc | 15 +++++++++++----
 src/canvas.h  |  1 +
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/canvas.cc b/src/canvas.cc
index 4af6355..e80d13c 100644
--- a/src/canvas.cc
+++ b/src/canvas.cc
@@ -86,10 +86,8 @@ Canvas::StreamPNG(const Arguments &args) {
   Canvas *canvas = ObjectWrap::Unwrap<Canvas>(args.This());
   closure_t closure;
   closure.fn = Handle<Function>::Cast(args[0]);
-  cairo_surface_write_to_png_stream(canvas->getSurface(), writeToBuffer, &closure);
-  Handle<Value> argv[2];
-  argv[0] = Null();
-  argv[1] = Integer::New(0);
+  cairo_status_t status = cairo_surface_write_to_png_stream(canvas->getSurface(), writeToBuffer, &closure);
+  Handle<Value> argv[2] = { Null(), Integer::New(0) };
   closure.fn->Call(Context::GetCurrent()->Global(), 2, argv);
   return Undefined();
 }
@@ -110,6 +108,15 @@ Canvas::~Canvas() {
   cairo_surface_destroy(_surface);
 }
 
+/*
+ * Construct an Error from the given cairo status.
+ */
+
+Handle<Value>
+Canvas::Error(cairo_status_t status) {
+  return Exception::Error(String::New(cairo_status_to_string(status)));
+}
+
 /*
  * Save a PNG at the given path.
  */
diff --git a/src/canvas.h b/src/canvas.h
index bdf0d5b..c8a2e16 100644
--- a/src/canvas.h
+++ b/src/canvas.h
@@ -52,6 +52,7 @@ class Canvas: public node::ObjectWrap {
     static Handle<Value> New(const Arguments &args);
     static Handle<Value> SavePNG(const Arguments &args);
     static Handle<Value> StreamPNG(const Arguments &args);
+    static Handle<Value> Error(cairo_status_t status);
     inline cairo_surface_t *getSurface(){ return _surface; }
     static void blur(cairo_surface_t *surface, int radius);
     Canvas(int width, int height);

From 6e4a4fc1b200be72a5f3f2a88e068048ab596150 Mon Sep 17 00:00:00 2001
From: Tj Holowaychuk <tj@vision-media.ca>
Date: Wed, 27 Oct 2010 11:16:10 -0700
Subject: [PATCH 2/3] streamPNG sig is now (err, buf, len)

---
 lib/pngstream.js |  6 ++++--
 src/canvas.cc    | 19 ++++++++++---------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/lib/pngstream.js b/lib/pngstream.js
index 1966ea8..274b4f0 100644
--- a/lib/pngstream.js
+++ b/lib/pngstream.js
@@ -37,8 +37,10 @@ var PNGStream = module.exports = function PNGStream(canvas) {
   var self = this;
   this.canvas = canvas;
   process.nextTick(function(){
-    canvas.streamPNG(function(chunk, len){
-      if (len) {
+    canvas.streamPNG(function(err, chunk, len){
+      if (err) {
+        self.emit('error', err);
+      } else if (len) {
         self.emit('data', chunk, len);
       } else {
         self.emit('end');
diff --git a/src/canvas.cc b/src/canvas.cc
index e80d13c..f7e9b52 100644
--- a/src/canvas.cc
+++ b/src/canvas.cc
@@ -61,14 +61,11 @@ Canvas::New(const Arguments &args) {
 static cairo_status_t
 writeToBuffer(void *c, const uint8_t *data, unsigned len) {
   closure_t *closure = (closure_t *) c;
-  Handle<Value> argv[2];
   Buffer *buf = Buffer::New(len);
   memcpy(buf->data(), data, len);
-  argv[0] = buf->handle_;
-  argv[1] = Integer::New(len);
-  closure->fn->Call(Context::GetCurrent()->Global(), 2, argv);
+  Handle<Value> argv[3] = { Null(), buf->handle_, Integer::New(len) };
+  closure->fn->Call(Context::GetCurrent()->Global(), 3, argv);
   // TODO: CAIRO_STATUS_NO_MEMORY
-  // TODO: leak
   return CAIRO_STATUS_SUCCESS;
 }
 
@@ -79,16 +76,20 @@ writeToBuffer(void *c, const uint8_t *data, unsigned len) {
 Handle<Value>
 Canvas::StreamPNG(const Arguments &args) {
   HandleScope scope;
-  // TODO: error handling
-  // TODO: nonblocking
+  // TODO: async
   if (!args[0]->IsFunction())
     return ThrowException(Exception::TypeError(String::New("callback function required")));
   Canvas *canvas = ObjectWrap::Unwrap<Canvas>(args.This());
   closure_t closure;
   closure.fn = Handle<Function>::Cast(args[0]);
   cairo_status_t status = cairo_surface_write_to_png_stream(canvas->getSurface(), writeToBuffer, &closure);
-  Handle<Value> argv[2] = { Null(), Integer::New(0) };
-  closure.fn->Call(Context::GetCurrent()->Global(), 2, argv);
+  if (status) {
+    Handle<Value> argv[1] = { Canvas::Error(status) };
+    closure.fn->Call(Context::GetCurrent()->Global(), 1, argv);
+  } else {
+    Handle<Value> argv[3] = { Null(), Null(), Integer::New(0) };
+    closure.fn->Call(Context::GetCurrent()->Global(), 3, argv);
+  }
   return Undefined();
 }
 

From d89dd26d1a1341e03510b3ac95c493b82d3bf4cc Mon Sep 17 00:00:00 2001
From: Tj Holowaychuk <tj@vision-media.ca>
Date: Wed, 27 Oct 2010 11:17:36 -0700
Subject: [PATCH 3/3] Comment

---
 src/canvas.cc | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/canvas.cc b/src/canvas.cc
index f7e9b52..b5f1c0b 100644
--- a/src/canvas.cc
+++ b/src/canvas.cc
@@ -65,7 +65,6 @@ writeToBuffer(void *c, const uint8_t *data, unsigned len) {
   memcpy(buf->data(), data, len);
   Handle<Value> argv[3] = { Null(), buf->handle_, Integer::New(len) };
   closure->fn->Call(Context::GetCurrent()->Global(), 3, argv);
-  // TODO: CAIRO_STATUS_NO_MEMORY
   return CAIRO_STATUS_SUCCESS;
 }