Implementation and Benchmarking of plotting function

[Lars Jahr Røine]

Hello,

I asked a question about this on #Octave and wad advised to post my 
question here.

I've implemented a plotting function for plotting unstructured grids as 
an addition to a open source matlab toolbox which is currently being 
ported to Octave. My code is in C++ using OpenGL. I've now managed (I 
think) to move the functionality into the Octave C++ source code, but I 
run into problems when I try to benchmark.

What I've done so far is to implement a class Grid in  grid.hpp and 
included this in gl-render.h. I'm also using a simple fps counter which 
I have included (FpsCounter.hpp). I have then made a new function in the 
opengl_renderer class called draw_unstructured_grid(const 
grid::properties &props), where grid::properties is a class I've 
implemented in the file graphics.h.in. In addition I've made a script 
file in /octave/scripts/plot/ called plot_grid.m which checks the input 
before sending it to the C++ code.  I have made some modifications in 
the makefiles in /octave and in /octave/src (Which probably should be 
done in a different way, since I've now come to understand that the 
Makefiles shouldn't be modified directly). Here I have added -lGLEW a 
couple of places.

At first I had both a grid.hpp and a grid.cpp file, but then I got 
compile errors because the compiler couldn't find the files that where 
declared in grid.hpp but implemented in grid.cpp. I now assume this is 
because I didn't do anything to link my own code into octave. I noticed 
however that I was able to call functions that where fully implemented 
in the header file, grid.hpp. I therefore moved the entire 
implementation into grid.hpp and got my code to work. I am positive it 
works since I'm able to call my new plot_grid function from Octave, and 
I get a correct plot up and running. Debug print that I have in the 
methods in the grid class are also printed when running the Octave 
command. The fps-counter prints out results (incorrectly, but still it 
prints). How is this possible when I haven't linked my own code with the 
rest of the Octave code? (I guess this is more of a general C++ 
question, but still I hope I could get some help). And more importantly, 
how should I attack the problem of using both header and source files in 
Octave. Where do I make modifications so that my code is linked into the 
Octave code?

I originally thought I had gotten around the linkage problem by 
implementing all the code in the header-files until I tried to do some 
benchmarks. My idea was to make a large/infinite loop inside the draw 
function in /octave/src/DLD-FUNCTIONS/__init_fltk__.cc and then count 
the frames drawn inside the function I have implemented in the 
opengl_renderer class (draw_unsctructured_grid). When I did this the 
plots did not however appear (only the fltk window) until after the loop 
had finished. I got a tip from #Octave to call __fltk_redraw__() each 
time in the loop. To do this I had to forward declare __fltk_redraw__ 
because it is found in a later stage in the source file than the draw 
function. Octave compiles just fine, but I get an error when I call 
graphics_toolkit("fltk"):

error: feval: /octave/src/DLD-FUNCTIONS/__init_fltk__.oct: failed to 
load: /octave/src/DLD-FUNCTIONS/__init_fltk__.oct: undefined symbol: 
_ZN11OpenGL_fltk15__fltk_redraw__Ev
error: called from:
error:   
/home/lars/master/master_repo/larsjr-master/octave-dev/octave/scripts/plot/graphics_toolkit.m 
at line 56, column 5

I would appreciate all advice on how to solve these problems, and 
explanations on what I'm doing wrong :) It would be very interesting to 
learn how to change Octave's build system in a correct way.

Regards,

Lars