XdbeGetVisualInfo(3)

💖 XdbeGetVisualInfo — bestie edition 💖

okay so this is a page from the X FUNCTIONS manual, and it's all about XdbeGetVisualInfo(3). yes that's the whole title, no notes, she's iconic like that ✨

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✨ NAME ✨

XdbeGetVisualInfo — get dbe Visual Information 👑

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🌸 SYNOPSIS 🌸

#include <X11/extensions/Xdbe.h>

XdbeScreenVisualInfo *XdbeGetVisualInfo(
    Display  *dpy,
    Drawable *screen_specifiers,
    int      *num_screens)

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💅 DESCRIPTION 💅

okay bestie, listen. this function is literally just handing you the tea about which visuals support double buffering 🫶

so num_screens tells her how many elements are chilling in the screen_specifiers list. and each drawable in screen_specifiers? it's designating a screen — like, "hey, I want the supported visuals for this one please" 💁‍♀️

but here's the plot twist: if num_screens is zero, then you're requesting info for all screens, periodt. and in that case, when the function comes back, num_screens gets set to the number of screens that were found 👀

if an error happens, this function returns NULL. otherwise? she returns a pointer to a list of XdbeScreenVisualInfo structures of length num_screens 🌈

now the mapping, and this matters:

• the *n*th element in the returned list corresponds to the *n*th drawable in the screen_specifiers list
• UNLESS num_screens was passed in with the value zero — in which case the *n*th element in the returned list corresponds to the *n*th screen of the server, starting with screen zero 🌟

the XdbeScreenVisualInfo structure 🎀

she has these fields, and yes we're keeping them exactly:

int            count
XdbeVisualInfo *visinfo

• count — specifies the number of items in visinfo
• visinfo — specifies a list of visuals, depths, and performance hints for this screen

the XdbeVisualInfo structure 🦋

and this one has:

VisualID visual
int      depth
int      perflevel

• visual — specifies one visual ID that supports double-buffering
• depth — specifies the depth of the visual
• perflevel — a performance hint

now about perflevel, because the way this is worded is very specific and we're respecting it: the only operation defined on a perflevel is comparison to a perflevel of another visual on the same screen. the visual having the higher perflevel is likely to have better double-buffering graphics performance than the visual having the lower perflevel 🔥

and you literally cannot deduce anything from these, no cap: - the magnitude of the difference of two perflevels - a perflevel value in isolation - comparing perflevels from different servers

like, don't do it. it's giving undefined vibes and it will not slay 😭

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💀 ERRORS 💀

• BadDrawable — one or more values passed in screen_specifiers is not a valid drawable. (rude, honestly 🙈)

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👑 SEE ALSO 👑

DBE, XdbeAllocateBackBufferName(), XdbeBeginIdiom(), XdbeDeallocateBackBufferName(), XdbeEndIdiom(), XdbeFreeVisualInfo(), XdbeGetBackBufferAttributes(), XdbeQueryExtension(), XdbeSwapBuffers() 🫶

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okay that's the whole page, mwah 💋 this was X Version 11, libXext 1.3.6, and yeah XdbeGetVisualInfo(3) — go forth and double buffer, bestie, you ate 💖✨🎀