GLXUSEXFONT(3gl)

💅 GLXUSEXFONT — the glXUseXFont page, GLX edition (section 3G, bestie)

okay so this is the whole entire manual page for glXUseXFont, and yes we're doing it with full group-chat energy because you deserve it. it lives in the GLX section of the manual (that's the 3G bit, iykyk), and it's literally about turning X font glyphs into bitmap display lists. iconic behaviour tbh. 🎀

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✨ NAME ✨

glXUseXFont — create bitmap display lists from an X font 🦋

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🌸 C SPECIFICATION 🌸

void glXUseXFont( Font font,
                  int first,
                  int count,
                  int listBase )

also there's a little formatting incantation tucked in here, delim $$, which is just the page doing its own thing. not your problem, but it's there, and we keep it because we keep everything. 💖

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🎀 PARAMETERS 🎀

• font — the font we're stealing glyphs from. this is where the character glyphs come from, bestie.
• first — the index of the first glyph we're taking. like, where the grabby hands start. 🙈
• count — how many glyphs we're taking. the number. the amount. the whole vibe.
• listBase — the index of the first display list that's gonna get generated. the starting point of the list situation. ✨

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👑 DESCRIPTION 👑

so glXUseXFont generates count display lists, named listBase through listBase+count-1, and each one contains a single glBitmap command. periodt.

the parameters of the glBitmap command in display list listBase+i are derived from glyph first+i. let's break that down because the math is the moment:

• xorig, yorig, width, and height are computed from font metrics as descent-1, -lbearing, rbearing-lbearing, and ascent+descent, respectively.
• xmove is taken from the glyph's width metric.
• ymove is set to zero.
• and finally, the glyph's image gets converted to the appropriate format for glBitmap. slay. 💅

using glXUseXFont may be more efficient than accessing the X font and generating the display lists explicitly. why? two reasons, and both are lowkey genius:

• the display lists are created on the server without requiring a round trip of the glyph data.
• the server may choose to delay the creation of each bitmap until it is accessed.

empty display lists are created for all glyphs that are requested and are not defined in font. so like, no glyph, no problem, you still get an empty list. 🫶

and glXUseXFont is ignored if there is no current GLX context. nothing happens. the call simply does not eat. 💀

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🔥 ERRORS 🔥

• BadFont is generated if font is not a valid font.
• GLXBadContextState is generated if the current GLX context is in display-list construction mode.
• GLXBadCurrentWindow is generated if the drawable associated with the current context of the calling thread is a window, and that window is no longer valid.

ngl those last two are the ones that sneak up on you. check your context state and check your window, bestie. 🌈

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⭐ SEE ALSO ⭐

• glBitmap
• glXMakeCurrent

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and that's the whole page!! this was GLXUSEXFONT() from the GLX corner of the manual, and yes we said goodbye in exactly that form because that's how the page signs off. go forth and make bitmap display lists. you got this. mwah. 💖✨🎀🦋