"NativeClient: NaCl module crashed" when flushing pp::Graphics2D - c++

Question

I'm trying to get familiar with Graphics2D for NaCl, but I'm getting the error "NativeClient: NaCl module crashed" when I try to paint and flush my Graphics2D instance.
Here is the output of my calls to console.log:
View did change
Making graphics context
Drawing
Making blank image data
PaintAndFlush
Flush
I am on main thread
NativeClient: NaCl module crashed
Here is my index.html : https://jsfiddle.net/3c1y4wp9/
And here is my c++ code:
#include <deque>
#include "ppapi/cpp/instance.h"
#include "ppapi/cpp/module.h"
#include "ppapi/cpp/var.h"
#include "ppapi/cpp/graphics_2d.h"
#include "ppapi/cpp/image_data.h"
#include "ppapi/cpp/instance.h"
#include "ppapi/cpp/module.h"
#include "ppapi/cpp/var.h"
#include "ppapi/cpp/var_array.h"
#include "ppapi/utility/completion_callback_factory.h"
namespace {
const uint32_t kBlue = 0xff4040ffu;
const uint32_t kBlack = 0xff000000u;
}
class GravitySimInstance : public pp::Instance {
public:
explicit GravitySimInstance(PP_Instance instance) : pp::Instance(instance)
{}
virtual ~GravitySimInstance() {}
private:
virtual void HandleMessage(const pp::Var& var_message) {
}
void PaintAndFlush(pp::ImageData* image_data) {
PostMessage("PaintAndFlush");
assert(!flushing_);
graphics_2d_context_.ReplaceContents(image_data);
PostMessage("Flush");
if (pp::Module::Get()->core()->IsMainThread()) {
PostMessage("I am on main thread");
} else {
PostMessage("I am NOT on main thread");
}
graphics_2d_context_.Flush(
callback_factory_.NewCallback(&GravitySimInstance::DidFlush));
flushing_ = true;
}
void DidFlush(int32_t error_code) {
PostMessage("DidFlush");
flushing_ = false;
}
virtual void DidChangeView(const pp::View& view) {
PostMessage("View did change");
if (size_ != view.GetRect().size()) {
size_ = view.GetRect().size();
const bool is_always_opaque = true;
PostMessage("Making graphics context");
graphics_2d_context_ = pp::Graphics2D(this, view.GetRect().size(),
is_always_opaque);
BindGraphics(graphics_2d_context_);
Draw();
}
}
void Draw() {
PostMessage("Drawing");
pp::ImageData image_data = MakeBlankImageData(size_);
PaintAndFlush(&image_data);
}
pp::ImageData MakeBlankImageData(const pp::Size& size) {
PostMessage("Making blank image data");
const bool init_to_zero = false;
pp::ImageData image_data = pp::ImageData(this,
PP_IMAGEDATAFORMAT_BGRA_PREMUL,
size,
init_to_zero);
uint32_t* image_buffer = static_cast<uint32_t*>(image_data.data());
for (int i = 0; i < size.GetArea(); ++i)
image_buffer[i] = kBlack;
return image_data;
}
pp::Graphics2D graphics_2d_context_;
pp::CompletionCallbackFactory<GravitySimInstance> callback_factory_;
/// The size of our rectangle in the DOM, as of the last time DidChangeView
/// was called.
pp::Size size_;
/// true iff we are flushing.
bool flushing_;
/// Stores the most recent histogram so that we can re-draw it if we get
/// resized.
double histogram_[10];
};
class GravitySimModule : public pp::Module {
public:
GravitySimModule() : pp::Module() {}
virtual ~GravitySimModule() {}
virtual pp::Instance* CreateInstance(PP_Instance instance) {
return new GravitySimInstance(instance);
}
};
namespace pp {
Module* CreateModule() {
return new GravitySimModule();
}
} // namespace pp

Answer 1

Nothing looks obviously wrong, except where you initialize the image buffer. You need to take the stride into consideration when working with the image data. However, it doesn't look like you're writing out of bounds. Have you tried making init_to_zero true and using the ImageData as is to see if it still crashes?

Answer 2

Try calling of Flush function only in main thread. If you want to call such functions (which should be called in main thread) from working thread call them throuth pp::Core::CallOnMainThread function.