Modify the format0 length limit.

[lwang1997]

Description

This Pull Request fixes a bug in the lv_font_conv tool where the list_length in LV_FONT_FMT_TXT_CMAP_FORMAT0_FULL type cmap could exceed 255, causing memory allocation issues and incorrect character mapping. The issue was identified when using the symbols parameter, which led to the generation of a glyph_id_ofs_list with 256 elements.

Changes Made

• Modified the cmap_split function to ensure that the character range length does not exceed 255.

Related Issue

• This Pull Request addresses issue When using this tool to generate a CJK font library, I encountered an issue that causes an error when loading the font. #118. Please refer to the issue for more details: When using this tool to generate a CJK font library, I encountered an issue that causes an error when loading the font. #118

Testing

• Tested with various character ranges to ensure list_length does not exceed 255.
• Verified that the generated font files have correct character mappings.

[kisvegabor]

Thank you! Could you also update the test?