Create array of predefined arrays

Question

With the help of PlatformIO and the U8G2 library, I want to write an application for an ESP8266 microcontroller. The U8G2 offers countless fonts, and I would like to display them on a graphical display so that I can select the appropriate ones. Each font is defined as follows:

extern const uint8_t u8g2_font_logisoso50_tn[] U8G2_FONT_SECTION("u8g2_font_logisoso50_tn");

about 2000 different way, where the macros are defined as

#define U8G2_FONT_SECTION(name) U8X8_FONT_SECTION(name)
...
#  define U8X8_FONT_SECTION(name) __attribute__((section(".text." name)))
...
typedef __uint8_t uint8_t ;
...
typedef unsigned char __uint8_t ;

The font is displayed by a function

void setFont(const uint8_t *font)

I want to create an array from the list of fonts, which I can iterate through and show them one by one on the display.

const char* fonts[] = {
  "u8g2_font_u8glib_4_tf",
  ...
};

and display using this:

u8g2.setFont( U8G2_FONT_SECTION(fonts[pos]) );

but the compiler gives error as follows:

In file included from .pio\libdeps\d1\U8g2\src/U8x8lib.h:47,
                 from .pio\libdeps\d1\U8g2\src/U8g2lib.h:53,
                 from src\main.cpp:2:
src\main.cpp: In function 'void put()':
.pio\libdeps\d1\U8g2\src/clib/u8x8.h:162:35: error: expected primary-expression before '__attribute__'
  162 | #  define U8X8_FONT_SECTION(name) __attribute__((section(".text." name)))
      |                                   ^~~~~~~~~~~~~
.pio\libdeps\d1\U8g2\src/clib/u8g2.h:188:33: note: in expansion of macro 'U8X8_FONT_SECTION'
  188 | #define U8G2_FONT_SECTION(name) U8X8_FONT_SECTION(name)
      |                                 ^~~~~~~~~~~~~~~~~
src\main.cpp:18:20: note: in expansion of macro 'U8G2_FONT_SECTION'
   18 |   uint8_t font[] = U8G2_FONT_SECTION(fonts[pos]);
      |                    ^~~~~~~~~~~~~~~~~
*** [.pio\build\d1\src\main.cpp.o] Error 1

What else should I write?

Looking at your question, I see no error message. When I copy the code from the question and try to compile it, I get the error error: expected unqualified-id before '...' token. Is that the error I should be looking at? Or should I assume you decided to make answering harder by using ... instead of // ...? (Please do assume that someone will copy the code from the question directly into an online compiler and try to compile it. Making this process as easy as possible makes it more likely to get help.) — JaMiT
– JaMiT, Commented Nov 24, 2023 at 19:20
It might be worth the time to review How to Ask and minimal reproducible example. It would be better to start with the question and save your program's goal for the end. The question is relevant to the question, so should be in a prominent location (the beginning). The larger picture of your program might be relevant, but also might not be, so move it to the end to make it easier to skip if it's not relevant. — JaMiT
– JaMiT, Commented Nov 24, 2023 at 19:25
The U8G2_FONT_SECTION macro only makes sense in the context of a global variable declaration. Why do you want to use it when referencing your array elements? Why not just use something like const uint8_t* fonts[] = { u8g2_font_u8glib_4_tf, ... }; const uint8_t* font = fonts[pos];? — Miles Budnek
– Miles Budnek, Commented Nov 24, 2023 at 20:08

Michaël Roy · Accepted Answer · 2023-12-20 15:22:58Z

Simply define an array of pointers:

Example:

const uint8_t* fonts[] = {
  u8g2_font_u8glib_4_tf,
  u8g2_font_u8glib (etc...) ,
  ...
};

You can be a bit more inventive and crate a map:

struct font_info
{
    const char* name;
    const uint8_t* font;
};

// use a stringifying macro to painlessly generate displayable names 
// for your fonts
#define FONT_INFO(x)  font_info{ #x, x }

const font_info fonts[] = 
{
    FONT_INFO(u8g2_font_u8glib_4_tf),
    FONT_INFO(u8g2_font_u8glib (whatever the next one is...),
    ...
};

// later...

for (const auto& f : fonts)
{
    display_font_name(f.name);   // your own display function
    u8g2.setfont(f.font);
    display_font_sample_text();  // your own text sample display function
    wait_for user_input();       // you'll need to wait a bit so the user 
                                 // can see the font being displayed.
};

Or something close to that, so you can display the font name as well, if needed.

Collectives™ on Stack Overflow

Create array of predefined arrays

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related