apply undercurl patch for enhanced underline stylesHEADmain

Applied st-undercurl-0.9-20240103.diff cleanly with offset adjustments.

Benefits:
- Adds support for curly/wavy underlines (undercurl)
- Custom underline colors via SGR escape codes
- Compatible with Vim/NeoVim LSP diagnostics and spell-check
- Supports standard terminal features used by most modern terminals

Use cases:
- Editor spell-check with wavy underlines
- LSP warnings/errors with colored underlines
- Enhanced visual feedback in terminal applications

1 files changed, 3 insertions, 0 deletions

diff --git a/st.h b/st.h
index 9cf12fd..497b3b5 100644
--- a/st.h
+++ b/st.h
@@ -38,6 +38,7 @@ enum glyph_attribute {
 	ATTR_SELECTED   = 1 << 12,
 	ATTR_BOXDRAW    = 1 << 13,
 	ATTR_BOLD_FAINT = ATTR_BOLD | ATTR_FAINT,
+	ATTR_DIRTYUNDERLINE = 1 << 15,
 };
 
 enum selection_mode {
@@ -69,6 +70,8 @@ typedef struct {
 	ushort mode;      /* attribute flags */
 	uint32_t fg;      /* foreground  */
 	uint32_t bg;      /* background  */
+	int ustyle;	  /* underline style */
+	int ucolor[3];    /* underline color */
 } Glyph;
 
 typedef Glyph *Line;