define LV_FS_WIN32_LETTER "\0" error with lv_image_src_get_type

[USTHzhanglu]

LVGL version

v9.0.0

Platform

windows SDL2 with vscode

What happened?

lv_image_set_src: failed to get image info: 0x7ff7687c20e0 lv_image.c:175

and no img show
change \0 -> A ok
if path error it always show str

lv_image_set_src: failed to get image info: A:test.jpeg lv_image.c:175

How to reproduce?

lv_image_set_src(image1, "\0:test.jpeg");

[USTHzhanglu]

lv_image_src_get_type dont think \0` is file path.

    /*The first byte shows the type of the image source*/
    if(u8_p[0] >= 0x20 && u8_p[0] <= 0x7F) {
        return LV_IMAGE_SRC_FILE; /*If it's an ASCII character then it's file name*/
    }
    else if(u8_p[0] >= 0x80) {
        return LV_IMAGE_SRC_SYMBOL; /*Symbols begins after 0x7F*/
    }
    else {
        return LV_IMAGE_SRC_VARIABLE; /*`lv_image_dsc_t` is draw to the first byte < 0x20*/
    }

but lv_conf_template.h make default LETTER as \0. if I use it directly, it will error.
maybe change the lv_conf_template.h?

[vwheeler63]

Actually, I think the error is in the comment in lv_conf_template.h. It is my understanding that if one uses lv_fs_win32.c or anything that uses it (e.g. File Explorer), that it is a requirement of the programmer to change '\0' to a driver identifier of their choosing. However, given the way that macro is used (to provide a default value for the driver.letter field), I find that the instruction in the comment for this macro is misleading. Currently it is:

/**< Set an upper cased letter on which the drive will accessible (e.g. 'A') */

but it seems to me that it should be

/**< Set an upper cased letter to be the identifier for this file-system driver (e.g. 'A').  See docs under File System > Identifier Letters. */

Once done, then the call above that causes it should be (assuming 'A' as the driver identifier):

lv_image_set_src(image1, "A:C:/path/to/test.jpeg");  /* If drive and directory should be specified. *
lv_image_set_src(image1, "A:test.jpeg");  /* If default drive and directory are already correct. *

@liamHowatt , what do you think?

[liamHowatt]

It was fixed by #6367 (and improved by #6986). Are you able to use a newer version of LVGL? It generates a compile-time error if a driver letter is '\0' now.

[USTHzhanglu]

It was fixed by #6367 (and improved by #6986). Are you able to use a newer version of LVGL? It generates a compile-time error if a driver letter is '\0' now.

oh, i used lv_port_pc_vscode with [lvgl @ 8691574](https://github.com/lvgl/lvgl/tree/8691574c5bc8a84352d851d709e6d8c6d24fd624). the newer version of LVGL tell me error: "Invalid drive letter",it`s very useful