Allowing plugins to talk to eachother?

On 14/01/2013 at 13:11, xxxxxxxx wrote:

No worries. Happens to me all the time.
I've got most of your code in place. But I'm afraid it's not working for me.
The Bitmap button is always blank.

The only code I couldn't use at all was this:

Bool PluginStart() {  
  Bool success;  
  success = MyDialog::InitStatic();  
  if (!success) {  
      MessageDialog("MyDialog class could not initialize internals.");  
      return FALSE;  
  // Register Command and Tag and stuff you need..  

I'm guessing you want me to put that in the main.cpp file?
I couldn't make it work. But it looks like that just handles a no image found scenario. And shouldn't stop the plugin from working if there's an image in the tag.

You also used an Auto type C++ 11 feature that didn't work for me. I don't think the SDK supports this new C++ feature yet.
So I wrote it this way instead:

  switch (type)  
      // Handle our custom message here !  
          // C++11 Feature!  
          //auto data = (PMSG_GetSampleImageData* ) data;  //<--Not supported by the SDK?  
          PMSG_GetSampleImageData *data = gNew PMSG_GetSampleImageData;  
          data->supported = TRUE;  
          data->bmp = image;  

I'm not sure if it's correct. But is doesn't crash.

I see what you're trying to do. But it's not working for me.
I'm still a learner with this C++ stuff so I might be doing something wrong.

Thanks anyway for trying to help,

On 14/01/2013 at 14:44, xxxxxxxx wrote:

Hi Scott!

The PluginStart() function from above should just give you a hint that I intended
MyDialog::InitStatic() to be called so that MyDialog::defaultImage will be initialized (and
that it will be handled when this method returned FALSE). It should not cover your complete
PluginStart() implementation (didn't even take a close look at yours).

The auto keyword is a C++11 feature supported by VC2010 and newer. It is just a shortcut
so you don't have to write the type identifier twice. Therefore, the correct non-C++11 version
of that line is as follows:

PMSG_GetSampleImageData* data = (PMSG_GetSampleImageData* ) msgData;

while msgData is the second parameter from the MyTag::Message() method (being a void*
pointer that needs to be casted into the expected data-type). In your version of the code,
you do not pass the requested data to the informant (sender of the message), but instead,
you create a new data object temporarily and freeing it afterwards. This is why we pass the
address of our data object to the message so the tag can fill in the data and we can retrieve it.

I'll try to set up some working and compiling code as soon as I have the time for it!


On 14/01/2013 at 15:28, xxxxxxxx wrote:

Ok. Thanks Niklas.

There's so many parts to these C++ plugins it's really hard to cover something like this with code snippets. It's not like sharing python code. There's too many places it can go wrong.
I had hoped that by providing a complete example it would lesson the burden of people trying to help me. And they could just edit my code without having to build it all from scratch.

I appreciate the help,

On 15/01/2013 at 04:40, xxxxxxxx wrote:

Hi Scott,

I've spent my last three hours working on a complete plugin. You definately owe
me a beer, okay? Windows x86 build is included. To build it on your own, you
must add threee new include paths to your VC project (I build from the command
line that is why the VC project is not included). These are ./ ./include and
../../resource/modules/xtensions/res/description/ (to include
drendersettings.h from PComUtils.h).

When you open the dialog, you will see an image showing a red exclamation mark
with the text "not supported". This image is shown in the BitmapButton when
no Tag is selected or the Tag does not respond positive to the
MSG_PCOM_CANSETBITMAP message. When you create a PComTag on an object and
select it, the image shown in the dialog will turn into a green one with the
word "Render". This happens due to the fact that the PComTag responds positive
to the MSG_PCOM_CANSETBITMAP message and additionally does not have an
internal bitmap assigned yet. When you click on that "Render" image, it will
turn into an image of the current scene (just like in your example). The
MSG_PCOM_SETBITMAP message is sent and the PComTag will store the rendered
image internally. When selecting another Tag, you will again see the red
exclamation mark. Selecting the PComTag again will display the stored image.
The image is retrieved from a Tag by sending the MSG_PCOM_RETRIEVEBITMAP
message. Clicking on the button when the stored image is displayed will
remove the image from the tag by sending MSG_PCOM_SETBITMAP with a NULL pointer
instead of a valid address to a bitmap (which by definition of the message
type states, that the internal image should be removed).

Best wishes,

On 15/01/2013 at 09:07, xxxxxxxx wrote:

Wow.That's really great.
Thanks a lot Niklas. :beer:

Sorry it took up so much of your time.


On 25/01/2013 at 08:58, xxxxxxxx wrote:

Has anyone ever used friend classes within these C4D plugins?
In some cases it would be much less complicated if the two plugins simply had access to each others class members. Rather than using a third party interface to make them communicate.

I've Googled about friend classes trying to learn how to write them.
But when I try to use them inside of these plugins. I can't get it to work.
I can set up the basic framework so it will compile without errors. But when I try to access the member variables from the other class. I get undefined type errors.


//Forward declare the tag so the Dialog can access it  
class MyTag;  
class MyDialog : public GeDialog  
      virtual blah, blah, blah;  
      virtual blah, blah, blah;  
      LONG dialogMemberVariable;  //A class member that the tag can also access  
      friend MyTag;  
//How do I access use the tagMemberVariable without getting undefined class errors?  
class MyTag : public TagData  
      virtual blah, blah, blah;  
      virtual blah, blah, blah;  
      LONG tagMemberVariable; //A class member that the dialog can also access  
      friend MyDialog;   
  //How do I access use the dialogMemberVariable without getting undefined class errors?  


On 27/01/2013 at 11:59, xxxxxxxx wrote:

Hi Scott,

The friend keyword allows the specified class to access protected and private attributes and
methods. Both of your classes have public members only, the friend keyword does not have any


On 27/01/2013 at 13:42, xxxxxxxx wrote:

Hiya Nik,

I learned a bit more about how to use friend yesterday.
I've a good raw C++ example now that I'm using as a learning tool:

//This is an example of using a custom method to access two different class's members  
//By making the method a friend of both of the classes  
#include <iostream>  
#include <string>  
using namespace std;  
class Class2;     //Forward declare Class2 so Class1 knows what's inside of it   
class Class1  
    int a, b;  
    Class1() : a(1), b(2) { }    //Constructor sets the class variable values  
    friend void change(Class1 c1, Class2 c2);  
class Class2  
    int j;  
    Class2() : j(3) { }        //Constructor sets the class variable value  
    friend void change(Class1 c1, Class2 c2);   
void change(Class1 &x1, Class2 &x2)  
  x1.a = 10;          //Changes the Class1 variable from 1 to 10  
  x2.j = 45;        //Changes the Class2 variable from 3 to 45  
      //Compare the members from the two different classes  
  if(x1.a < x2.j) cout << "Class1 member a is less than Class2 member j" <<endl;  
int main()  
  Class1 c1;  
  Class2 c2;  
  cout<< "Class1 member a= "<< c1.a <<endl;  
  cout<< "Class2 member j= "<< c2.j <<endl;  
  system("pause");   //Keeps the console open until the Enter key is pressed  
  return 0;  

The problem I'm having with this in C4D plugins is that we don't use main() quite the same way as in raw C++.
I think I need to place a prototype of the function that's the friend of the classes in the main.cpp file of C4D plugins. But I'm having a problem with the parameters part.

I can make a void type prototyped method without any parameters work fine in the C4D main.cpp file.
But when the method has params. in it ( In this cases the two classes). I'm having a hard time getting that to work in the main.cpp file.


On 27/01/2013 at 14:04, xxxxxxxx wrote:

Hi Scott,

I'm a little-bit confused. You never call the method check() of either class. The methods are defined,
but not implemented, nor ever referenced. What should this example actually demonstrate?

class A {
    friend B;

        void DoPrivateStuff();


        void DoPublicStuff();

class B {

        void DoPrivateStuff();


        void DoPublicStuff();

While class A has access to B::DoPublicStuff() only, class B has access to A::DoPublicStuff()
and A::DoPrivateStuff().


On 27/01/2013 at 14:16, xxxxxxxx wrote:

Oops. Sorry about that.
"check" should be "changed".
I changed it.

The problem I'm having is calling the changed() type function when doing it in a C4D plugin.
main() is written slightly differently in these C4D plugins.  And I'm having a problem with those differences.
Specifically. I'm having a hard time prototyping functions that have params. in them in the C4D main.cpp file.