thread '<unnamed>' panicked at crates\usvg\src\text\layout.rs:1505:35: begin > end (2 > 0) when slicing `الويب`

Hi,

My context is Windows 11 (latest public version), compiling with Visual Studio 2026. I use the static lib, built myself using cargo.

I have no problem in general with the library, but with at least one specific test file of yours I get a crash. I'm using this simple console app:

#include <Windows.h>
#include "E:\github\resvg\crates\c-api\resvg.h"
#pragma comment(lib, "E:\\github\\resvg\\target\\release\\resvg.lib")
#pragma comment(lib, "Ws2_32.lib")
#pragma comment(lib, "Userenv.lib")
#pragma comment(lib, "ntdll.lib")

int main()
{
    SetEnvironmentVariable(L"RUST_BACKTRACE", L"full");
    resvg_init_log();

    resvg_options* opt = resvg_options_create();
    resvg_options_load_system_fonts(opt);

    resvg_render_tree* tree;
    auto err = resvg_parse_tree_from_file("E:\\github\\resvg\\crates\\resvg\\tests\\tests\\text\\font-kerning\\arabic-script.svg", opt, &tree);
    ...
}

thread '<unnamed>' (32232) panicked at crates\usvg\src\text\layout.rs:1505:35:
begin > end (2 > 0) when slicing `الويب`
stack backtrace:
   0:     0x7ff6fbbea330 - std::backtrace_rs::backtrace::win64::trace
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\..\..\backtrace\src\backtrace\win64.rs:85
   1:     0x7ff6fbbea330 - std::backtrace_rs::backtrace::trace_unsynchronized
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66
   2:     0x7ff6fbbea330 - std::sys::backtrace::_print_fmt
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\sys\backtrace.rs:74
   3:     0x7ff6fbbea330 - std::sys::backtrace::impl$0::print::impl$0::fmt
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\sys\backtrace.rs:44
   4:     0x7ff6fbb96d61 - core::fmt::write
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\core\src\fmt\mod.rs:0
   5:     0x7ff6fbbfed14 - std::io::default_write_fmt
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\io\mod.rs:639
   6:     0x7ff6fbbfed14 - std::io::Write::write_fmt<std::sys::stdio::windows::Stderr>
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\io\mod.rs:1994
   7:     0x7ff6fbbb8c8f - std::sys::backtrace::BacktraceLock::print
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\sys\backtrace.rs:47
   8:     0x7ff6fbbb8c8f - std::panicking::default_hook::closure$0
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\panicking.rs:292
   9:     0x7ff6fbbda3fd - std::panicking::default_hook
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\panicking.rs:319
  10:     0x7ff6fbbda774 - std::panicking::panic_with_hook
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\panicking.rs:825
  11:     0x7ff6fbbb8dc4 - std::panicking::panic_handler::closure$0
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\panicking.rs:698
  12:     0x7ff6fbbb580f - std::sys::backtrace::__rust_end_short_backtrace<std::panicking::panic_handler::closure_env$0,never$>
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\sys\backtrace.rs:182
  13:     0x7ff6fbbb9e6e - std::panicking::panic_handler
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\std\src\panicking.rs:689
  14:     0x7ff6fbf56f7d - core::panicking::panic_fmt
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\core\src\panicking.rs:80
  15:     0x7ff6fbb972c0 - core::str::slice_error_fail_rt
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\core\src\str\mod.rs:102
  16:     0x7ff6fbf56918 - core::str::slice_error_fail
                               at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library\core\src\str\mod.rs:69
  17:     0x7ff6fbd79a21 - fontdb::Database::with_face_data::h2e96d068f96c7839
  18:     0x7ff6fbd7387d - fontdb::Database::with_face_data::h2e96d068f96c7839
  19:     0x7ff6fbdaa610 - usvg::text::layout::layout_text::haf4a225e1f32f647
  20:     0x7ff6fbca4f59 - usvg::text::convert::h0ed7e4b2f301ab3a
  21:     0x7ff6fbc84424 - usvg::parser::text::convert::h55affc065c43c436
  22:     0x7ff6fbc51330 - usvg::parser::converter::convert_children::h57cf2bc760faf6f6
  23:     0x7ff6fbc5110a - usvg::parser::converter::convert_element::ha79f7227414b3921
  24:     0x7ff6fbc4fc24 - usvg::parser::converter::convert_group::h96224e70dbab6bfb
  25:     0x7ff6fbc50f01 - usvg::parser::converter::convert_element::ha79f7227414b3921
  26:     0x7ff6fbc511a3 - usvg::parser::converter::convert_children::h57cf2bc760faf6f6
  27:     0x7ff6fbc5110a - usvg::parser::converter::convert_element::ha79f7227414b3921
  28:     0x7ff6fbc4fc24 - usvg::parser::converter::convert_group::h96224e70dbab6bfb
  29:     0x7ff6fbc50f01 - usvg::parser::converter::convert_element::ha79f7227414b3921
  30:     0x7ff6fbc511a3 - usvg::parser::converter::convert_children::h57cf2bc760faf6f6
  31:     0x7ff6fbc4a273 - usvg::parser::converter::convert_doc::hac73b42f39263787
  32:     0x7ff6fbc19bb9 - usvg::parser::<impl usvg::tree::Tree>::from_str::h9ff03229df6d0b95
  33:     0x7ff6fbc19d66 - usvg::parser::<impl usvg::tree::Tree>::from_data::hfedf69decc63a57b
  34:     0x7ff6fbb84da9 - resvg_parse_tree_from_file
  35:     0x7ff6fbf503f0 - main
                               at E:\smo\work\ConsoleApplication17\ConsoleApplication17.cpp:18
  36:     0x7ff6fbf50e29 - invoke_main
                               at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78
  37:     0x7ff6fbf50cd2 - __scrt_common_main_seh
                               at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
  38:     0x7ff6fbf50b8e - __scrt_common_main
                               at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:330
  39:     0x7ff6fbf50ebe - mainCRTStartup
                               at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_main.cpp:16
  40:     0x7ffb464ae8d7 - BaseThreadInitThunk
  41:     0x7ffb472cc3fc - RtlUserThreadStart

Start with crates/usvg/src/text/layout.rs at line 1505 and reproduce the panic using crates/resvg/tests/tests/text/font-kerning/arabic-script.svg through the reported C API setup. Run the relevant text and font-kerning tests after investigating the Arabic text path; done means the fixture parses and renders without the reported slicing panic.