XdbeSwapBuffers(3)

💖 XdbeSwapBuffers — the manual, but make it make sense 💖

okay bestie, so you know how this whole page is from the X FUNCTIONS part of the X library? yeah. and the function itself is called XdbeSwapBuffers, and it lives in manpage section 3 (that's the "C library functions" section, iykyk). let's get into it 🫶

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✨ NAME ✨

XdbeSwapBuffers — swaps front and back DBE buffers. that's it, that's the whole job. she flips them. iconic behavior honestly 💅

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🎀 SYNOPSIS 🎀

#include <X11/extensions/Xdbe.h>

Status XdbeSwapBuffers(
    Display      *dpy,
    XdbeSwapInfo *swap_info,
    int          num_windows)

three args, no notes. ✨

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🦋 DESCRIPTION 🦋

so what she DOES: this function swaps the front and back buffers for a whole list of windows. not just one. a list. she's a multitasker, she ate 🔥

• num_windows tells you how many windows are getting their buffers swapped — literally, it's the number of elements in the swap_info array. no more, no less.
• swap_info is the tea 🍵 — it's the per-window info the function needs to actually do each swap.

and the XdbeSwapInfo structure? she has these two fields:

     Window            swap_window
     XdbeSwapAction    swap_action

• swap_window — which window we're swapping buffers for.
• swap_action — which swap action to use for that swap_window. (they're a matched pair, a duo, a little unit 🫶)

now, swap_action is the interesting part, because it decides what happens to the new back buffer of the swap_window it's paired with — on top of making the old back buffer visible. the defined actions are:

• XdbeUndefined — the contents of the new back buffer become undefined. sounds scary but it's actually the efficient one: it lets the implementation just yeet the buffer contents if it wants to. fastest glow-up available 💀✨
• XdbeBackground — the unobscured region of the new back buffer gets tiled with the window background. this one lets devices use a fast clear capability during a swap, which is a slay.
• XdbeUntouched — the unobscured region of the new back buffer is left unmodified by the swap. she simply did not touch her.
• XdbeCopied — the unobscured region of the new back buffer becomes the contents of the old back buffer. copy-paste core 🎀

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🌸 ERRORS 🌸

she can throw hands (errors). here's the list, no skipping:

• BadMatch — you specified a window that isn't double-buffered, OR you specified the same window twice. rude. pick a lane bestie 😭
• BadWindow — you specified a window that's just... invalid. doesn't exist. ghosted.
• BadValue — you specified an invalid swap action. not a real one. made up. 💀

lowkey important: these are actual errors that get raised, not vibes. check your windows and your actions before you call her, fr fr.

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👑 SEE ALSO 👑

go read these next, bestie, they're all part of the same friend group:

• DBE
• XdbeAllocateBackBufferName()
• XdbeBeginIdiom()
• XdbeDeallocateBackBufferName()
• XdbeEndIdiom()
• XdbeFreeVisualInfo()
• XdbeGetBackBufferAttributes()
• XdbeGetVisualInfo()
• XdbeQueryExtension()

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and that's the whole page 🫶 this came to you courtesy of X Version 11 and libXext 1.3.6, and yes, this is XdbeSwapBuffers(3) — section 3, exactly where she belongs. go swap some buffers, you've got this 💖✨🌸