Where communities thrive


  • Join over 1.5M+ people
  • Join over 100K+ communities
  • Free without limits
  • Create your own community
People
Activity
    Alessandro Pignotti
    @alexp-sssup
    Cheerp is a C++ compiler for the Web platform and as such you need to port your application to use Web APIs instead of windows/macosx/linux APIs
    Cheerp provides the standard C and C++ library of course
    And support for GLES
    Waldemar Pawlaszek
    @laoo
    Hello. I'm experimenting with cheerp and I've found it to be a great software!
    I have one question: What is the clean way of exposing non trivial class to JavaScript? What I mean is a class that is a proxy to other C++ objects. The best thing what I've came up is something like this: 
    namespace client
{
  JSProxy * getProxy();
}

void loadCallback()
{
  __asm__( "window.proxy = new JSProxy();" );
  __asm__( "window.getProxy = function(){ return window.proxy; }" );

  JSProxy * pProxy = client::getProxy();

  pProxy->setModel( pModel );

  ...
}
    Waldemar Pawlaszek
    @laoo
    Obviously prefered way would be to create an object in C++ code and somehow assign it to global context, but I don't know how to do it, so I create it in JavaScript (like in example) and transfer the pointer to the C++ code via JavaScript function. I don't think it is meant to be done that way though.
    Alessandro Pignotti
    @alexp-sssup
    Have you seen this feature already? https://github.com/leaningtech/cheerp-meta/wiki/JavaScript-interoperability#the-jsexport-attribute
    Waldemar Pawlaszek
    @laoo
    I'm old enough to ask question only after reading the documentation :smile: To rephrase the question: is there a possibility to set the above-mentioned window.proxy object from C++ code without the external javascript function or __asm()__ inlining?
    Alessandro Pignotti
    @alexp-sssup
    Something like namespace client { extern JSProxy* proxy; } should work
    Waldemar Pawlaszek
    @laoo
    #include "JSProxy.hpp"

namespace client { extern JSProxy* proxy; }

void loadCallback()
{
  // [...]
  client::proxy = new JSProxy();
  // [...]
}
    Generates Uncaught ReferenceError: proxy is not defined in Chrome's console, so something is still not right. Thanks though. I managed to refactor it to something better anyway.
    Alessandro Pignotti
    @alexp-sssup
    You are right, global variables in the client namspace need to be already defined somewhere else in the JS code. For example the global 'document' variable works
    I'll take note to take a look at this, since arguably it is a bug that you are not allowed to initialize global variables from C++ code. Thanks for letting us notice this issue.
    rongzhou
    @rongzhou

    Hello there, Cheerp looks so great. I have a question. I wrote a small piece of code use 

    FILE *fp = fopen("text.txt", "r");
fclose(fp);

    It can be compile, but failed to execute said some variable no defined. I guess it need to link some library on compiler command?

    Alessandro Pignotti
    @alexp-sssup
    Hello @rongzhou, On the web platform it's not possible to access files using those synchronous APIs
    so they are unsupported
    Accessing a file over the network with fread would stall the whole browser UI in the meantime
    Take a look here https://github.com/leaningtech/cheerp-meta/wiki/Browser-side-programming-guide#loading-data-xmlhttprequest to find out how to use the XMLHttpRequest web api from C++ to load data over HTTP
    Sync access to files in Web workers context is not currently supported, but we plan to enable it in the future
    rongzhou
    @rongzhou
    Thanks
    I presumed there is a virtual file systems like Emscripten.
    Alessandro Pignotti
    @alexp-sssup
    That is not the case, we believe that the virtual file system approach is a toy. It's useful for small demos but it's not sustainable on real projects. You can achieve a result similar to the emscripten virtual filesystem by directly embedding files as strings. http://stackoverflow.com/questions/410980/include-a-text-file-in-a-c-program-as-a-char. This is probably fine for small files and configuration data, but we strongly advise to dynamically download resources as required using asynchronous xhr
    rongzhou
    @rongzhou
    Thanks again, I got it.
    Orangeyness
    @Orangeyness
    Hey, I ran into something which seems a bit odd.
    blob
    I have been trying to console.log a std::string which I have generated, however it kept showing in the console as an empty string.
    Took me a while to figure out but am I right in saying string literals aren't std strings?
    It seems like whenever I add a string literal to a std::string (like in the last line of code that I posted) the std::string gets tainted and logs as an empty string.
    Orangeyness
    @Orangeyness
    It's pretty unintuitive and inconvenient, the code compiles fine with no errors or warnings but doesn't behave how you'd expect.
    Alessandro Pignotti
    @alexp-sssup
    @Orangeyness I reproduced the bug, let me take a look
    Alessandro Pignotti
    @alexp-sssup
    @Orangeyness There is a bug in one variant of the std::string::insert method, I am working on it
    Orangeyness
    @Orangeyness
    Cheers mate.
    Alessandro Pignotti
    @alexp-sssup
    @Orangeyness Issue fixes in master, we make nightly builds for Ubuntu in our PPA but for other platforms you will need to wait for our next point release. It should happen pretty soon.
    Orangeyness
    @Orangeyness
    Thanks a lot.
    Ray Burgemeestre
    @rayburgemeestre
    Hi guys, awesome project, I'm just experimenting with the cheerp compiler a bit, and I was wondering.. is the following source file supposed to work or is this code not supported? http://cppse.nl/example.cpp.txt (without the std::sort() it works.)
    (The nodejs error message is included in the .txt)
    Alessandro Pignotti
    @alexp-sssup
    @rayburgemeestre You need to use the -cheerp-no-math-imul command line switch
    node.js (possibly only on some distros) do not have Math.imul
    With this command line switch cheerp will fall back to using plain * to implement integer multiplication, although this may cause precision issues in some cases
    Ray Burgemeestre
    @rayburgemeestre
    ah great, that works perfectly
    (I see in chrome it was working without that switch)
    Thank you
    Alessandro Pignotti
    @alexp-sssup
    @laoo You may be interested in knowing that the bug you reported a few weeks ago is fixed in git master. You can now define global variables in the client namespace.
    Waldemar Pawlaszek
    @laoo
    @alexp-sssup Thanks for the fix! I'm developing my toy project for the web in C++ and I have impression that client::String class could have been something more elaborate. For example lack of simple string comparison is problematic (at least in my scenario). Another thing: the exceptions is the thing for near of rather far future?
    Alessandro Pignotti
    @alexp-sssup
    Exceptions require complex performance trade offs on the Web platform, so do not expect support soon. About client::String, it is exactly the same String that you have in JS. What features would you need?
    Waldemar Pawlaszek
    @laoo
    @alexp-sssup Maybe I don't know about something. How to compare client::String againts literal string or another client::String the right way? I can always cast to std::string and use comparison operator, but it does not feel right for JS string to do so.
    Alessandro Pignotti
    @alexp-sssup
    You can compare the "pointers", they are JS references
    You still need to convert C++ literals to JS string for the comparison to work
    client::String == const char would not do the right thing, as they are both pointers
    client::String* == const char*