Thread: Help understanding the openVG api (fonts)

I've been using the OpenVG API (GitHub - ajstarks/openvg: Tools for exploring OpenVG) for a Raspberry Pi project i'm working on but i'm having trouble with adding new fonts.

As on the documentation. I built the c source file. I linked it and included it and this is were the problem is. It appears to me that you declare a variable (Fontinfo) and the documentation forgot a ; to end. I tried this and i get a segmentation fault I remove the ; and I get a compiler error. Now i'm totally lost and have no idea what to do and i'm not the most experienced so if anyone can grant me some insight that would be great.
Thank you!

Your question is incomprehensible.
What documentation?
What C source file?
What do you mean "linked it and include it"? C source files are not "included".
What Fontinfo and semicolon?

yes, i'm sorry. I read that after the fact and now it sounds crazy but its hard to explain my problem without describing the whole library and im not the most knowledgeable but I'll attempt to make some sense.

The library for openvg by ajstarks is the one i am using and is located at GitHub - ajstarks/openvg: Tools for exploring OpenVG.

The documentation for installing new fonts is at the bottom of the git hub page (third section from the bottom) titled "Using fonts".

starting from the top of the instructions, you are told to use a program provided called "font2openvg" witch essentially converts a .ttf file into a c source file witch only contains 8 different variables. The variables somehow combine to give you font data. This is where i believe the problem lies. The instructions say to include the created c source font file (DejaVuSans.inc) like a normal header file. then create a Fontinfo variable (At least i believe thats what he wants because he doesn't ad a semi colon to end the variable declaration... probably a mistake i just added on). one thing that bothers me is that this variable doesn't seam to be writing to, just created and read. the loadfont function mentioned after that doesn't provide much help.

This is the instructions posted.

Using fonts

Also included is the font2openvg program, which turns font information into C source that you can embed in your program. The Makefile makes font code from files found in /usr/share/fonts/truetype/ttf-dejavu/. If you want to use other fonts, adjust the Makefile accordingly, or generate the font code on your own once the font2openvg program is built.
font2openvg takes three arguments: the TrueType font file, the output file to be included and the prefix for identifiers. For example to use the DejaVu Sans font:

Code:

./font2openvg /usr/share/fonts/truetype/ttf-dejavu/DejaVuSans.ttf DejaVuSans.inc DejaVuSans

and include the generated code in your program:

Code:

#include "DejaVuSans.inc"
Fontinfo DejaFont

The loadfont function creates OpenVG paths from the font data:

Code:

loadfont(DejaVuSans_glyphPoints, 
        DejaVuSans_glyphPointIndices, 
        DejaVuSans_glyphInstructions,                
        DejaVuSans_glyphInstructionIndices, 
        DejaVuSans_glyphInstructionCounts, 
        DejaVuSans_glyphAdvances,
        DejaVuSans_characterMap, 
        DejaVuSans_glyphCount);

The unloadfont function releases the path information:

Code:

unloadfont(DejaFont.Glyphs, DejaFont.Count);

Note that the location of the font files may differ. (The current location for Jessie is /usr/share/fonts/truetype/ttf-dejavu) Use the FONTLIB makefile variable to adjust this location.

this is also the code for what i believe is the Fontinfo variable.

Code:

#ifndef OPENVG_FONTINFO_H
#define OPENVG_FONTINFO_H


#if defined(__cplusplus)
extern "C" {
#endif
    typedef struct {
        const short *CharacterMap;
        const int *GlyphAdvances;
        int Count;
        int descender_height;
        int font_height;
        VGPath Glyphs[500];
    } Fontinfo;


    extern Fontinfo SansTypeface, SerifTypeface, MonoTypeface;


#if defined(__cplusplus)
}
#endif                // OPENVG_FONTINFO_H
#endif

I did as you said and this is the result.

Code:

main: libshapes.c: 637: End: Assertion 'vgGetError() == VG_NO_ERROR' failed. 
(program exited with code: 134)

I guess I don't understand what you're trying to do, and I can't see your program from here, so ....

Can you get the client/hellovg.c program to work?

no you understand what i want but the errors are just so left field. I also thought i linked it at the top but i guess it didn't work so here it is.


the function getkey(012) is my function of i.h. i made it to wait for a key press and return the key.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/input.h>
#include <i.h>
#include "VG/openvg.h"
#include "VG/vgu.h"
#include "fontinfo.h"
#include "shapes.h"
#include "VG/Roboto.h"


int main(){
	
	int w, h;
	Fontinfo Roboto;
	
Roboto = loadfont(Roboto_glyphPoints, 
        Roboto_glyphPointIndices, 
        Roboto_glyphInstructions,                
        Roboto_glyphInstructionIndices, 
        Roboto_glyphInstructionCounts, 
        Roboto_glyphAdvances,
        Roboto_characterMap, 
        Roboto_glyphCount);
    Roboto.descender_height = Roboto_descender_height;
    Roboto.font_height = Roboto_font_height;
    
    initEvent();
     
    init(&w, &h);
    Start(w, h);
    Background(255,255,255);
    Fill(0,0,0,1);
    TextMid(300, 300, "Hello World", Roboto, 30);
    End();
    getKey(012);
    
    finish();
    
    
    exit(0);
}

What's in Roboto.h? Shouldn't it be called Roboto.inc? Could you check that it has the actual data (C code) in it? In this case you actually are including C code, which is not the norm.

Try commenting out "initEvent()" (whatever that is) and getKey(012). Replace getKey with:

Code:

    char s[99];
    fgets(s, sizeof s, stdin);  // wait for Enter key

The initEvent() function finds the keyboard file in /dev/input/by-path for getKey() to use and get press events.

I took your suggestion and it does work but i still get the same error. I'm starting looking though things for what i did wrong when making the file. I no longer believe that the problem is with my code. I think im using a wrong file (Roboto-regular.ttf). I'm thinking something about that file inst normal or compatible. im going to have to do a lot of work with building different files and hopefully i luck apon my problem. thanks for putting up with my incoherent messages.

Im starting to get frustrated with chasing my tail.