Question

Preamble

Using VTK library with C++, quite often I have to write something like this:

vtkInteractorStyleRubberBandZoom *isrbz = vtkInteractorStyleRubberBandZoom::New();

Furthermore, every time I need to use a new VTK class in my program, I have to go somewhere up the source file and add #include “vtkInteractorStyleRubberBandZoom.h”

How do I automate it, so I have to type each of the excruciatingly long class names one time instead of three?

I tried writing an Emacs minor mode for it. There are probably existing solutions out there already (YaSnippet?), but I thought that writing it myself would be a good excercise, too.

Code

;vtk-mode.el
;add to .emacs:
;(load  "vtk-mode")
;(global-set-key [(control =)] 'expand-vtk)

(defun expand-vtk ()
  (interactive)
  (setq now (point))
  (setq vtkstart (search-backward "vtk"))
  (setq vtkend (- (search-forward " ") 1))
  (setq vtkname (buffer-substring vtkstart vtkend))

  ;check for #include "vtkBlah.h"
  (setq includename (format "#include \"%s.h\"\n" vtkname))
  (search-backward includename nil (append-include-vtk includename))
  (goto-char (+ now (length includename)))

  (insert (format "= %s::New();" vtkname)))

(defun append-include-vtk (incname)
  (goto-char 0)
  (insert incname))

Problem

Basically, it works, except that searching for an include name always fails, e. g.:

vtkSomething *smth /*press C-= here, it looks backward for 
#include "vtkSomething.h", can't find it and 
calls append-include-vtk, adding it to the beginning 
of the file, then comes back here and expands this line into: */

vtkSomething *smth = vtkSomething::New();

//and let's add another instance of vtkSomething...
vtkSomething *smth2 /*press C-= again, it looks backward for 
#include "vtkSomething", and fails, despite the fact 
that it was added by the previous command. So it adds it again."*/

What am I doing wrong here with search-backward?

(there’s another (at least one) bug in the code, I shouldn’t add the (length includename) if the search-backward for it was successful, but for now I am more interested in how to make it successful, in the first place)

Answer 1

OK, I got it. Somehow I got an idea that the third argument of search-backward (noerror) is a callback, which it isn’t. Therefore it is evaluated every time, not just when the search fails. It should be something like this instead:

(defun expand-vtk ()
  (interactive)
  (setq now (point))
  (setq vtkstart (search-backward "vtk"))
  (setq vtkend (- (search-forward " ") 1))
  (setq vtkname (buffer-substring vtkstart vtkend))

  ;check for #include "vtkBlah.h"
  (setq includename (format "#include \"%s.h\"\n" vtkname))
  (if (search-backward includename nil t) 
      (goto-char now) 
      (progn (append-include-vtk includename) 
             (goto-char (+ now (length includename)))))  

  (insert (format "= %s::New();" vtkname)))

(defun append-include-vtk (incname)
  (goto-char 0)
  (insert incname))