If you want a "glyph" you are trolling yourself because selecting and assembling glyphs in fonts is an additional layer of punishing complication on top of Unicode itself. Correct text rendering requires passing as much text as possible (even multiple lines) to a "black box" library that figures out layout, ligatures, glyph replacement etc.
If instead you want to find, as is more likely, whole grapheme clusters that can be treated as editing units (e.g. select/copy/delete "the character after the cursor", move the cursor N "characters", count "letters" in a string) you can go forward through your string, codepoint by codepoint, and decide depending on how those codepoints are classified where a "character" ends. Your ideas and requirements about the criteria might or might not match those of your libraries and of the Unicode standard itself.
If instead you want to find, as is more likely, whole grapheme clusters that can be treated as editing units (e.g. select/copy/delete "the character after the cursor", move the cursor N "characters", count "letters" in a string) you can go forward through your string, codepoint by codepoint, and decide depending on how those codepoints are classified where a "character" ends. Your ideas and requirements about the criteria might or might not match those of your libraries and of the Unicode standard itself.