C++/Tk how to exequte general tcl code?

Question

So we have code like:

#include "cpptk.h" #include <stdio.h> using namespace Tk; void hello() { puts("Hello C++/Tk!"); } int main(int, char *argv[]) { static char* str = "button .a -text "Say Hello ppure TCL"\n" "pack .a\n"; init(argv[0]); button(".b") -text("Say Hello") -command(hello); pack(".b") -padx(20) -pady(6); runEventLoop(); }

imagine str is complex tcl code. We want to feed it to C++/Tk as a string. Also we want to have it exequted in the same TCL vm our general C++/Tk programm with gui we created in C++/Tk code runs. So the result of this code would be 2 buttons inside a window. How to do such thing?

How to do such thing?

Community · Accepted Answer · 2020-06-20 09:12:55Z

Have you got access to the Tcl_Interp* handle used inside C++/Tk? If so (and assuming here you've got it in a variable called interp) use:

int resultCode = Tcl_Eval(interp, str);

Next, check the resultCode to see if it is TCL_OK or TCL_ERROR (other values are possible, but uncommon in normal scripts). That tells you the interpretation of the “result”, which you get like this:

const char *result = Tcl_GetString(Tcl_GetObjResult(interp));

If the result code says its an error, result is now an error message. If it was ok, the result is the output of the script (NB: not what was written to standard out though). It's up to you what to do with that.

[EDIT]: I looked this up in more detail. It's nastier than it appears, because C++/Tk hides away Tcl quite deep inside itself. In so far as I can see, you do this (untested!):

#include "cpptk.h" // might need "base/cpptkbase.h" instead #include <string> // This next part is in a function or method... std::string script("the script to evaluate goes here"); std::string result = Tk::details::Expr(script,true);

If you haven't got the Tcl_Interp, you'll have to make one with Tcl_CreateInterp(). That's more complex though, and you won't be able to interact with the GUI from it.

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