104 lines
2.7 KiB
Go
104 lines
2.7 KiB
Go
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package xprop
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/*
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xprop/atom.go contains functions related to interning atoms and retrieving
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atom names from an atom identifier.
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It also manages an atom cache so that once an atom is interned from the X
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server, all future atom interns use that value. (So that one and only one
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request is sent for interning each atom.)
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*/
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import (
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"fmt"
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"github.com/jezek/xgb/xproto"
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"github.com/jezek/xgbutil"
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)
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// Atm is a short alias for Atom in the common case of interning an atom.
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// Namely, interning the atom always succeeds. (If the atom does not already
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// exist, a new one is created.)
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func Atm(xu *xgbutil.XUtil, name string) (xproto.Atom, error) {
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aid, err := Atom(xu, name, false)
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if err != nil {
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return 0, err
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}
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if aid == 0 {
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return 0, fmt.Errorf("Atm: '%s' returned an identifier of 0.", name)
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}
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return aid, err
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}
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// Atom interns an atom and panics if there is any error.
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func Atom(xu *xgbutil.XUtil, name string,
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onlyIfExists bool) (xproto.Atom, error) {
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// Check the cache first
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if aid, ok := atomGet(xu, name); ok {
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return aid, nil
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}
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reply, err := xproto.InternAtom(xu.Conn(), onlyIfExists,
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uint16(len(name)), name).Reply()
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if err != nil {
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return 0, fmt.Errorf("Atom: Error interning atom '%s': %s", name, err)
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}
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// If we're here, it means we didn't have this atom cached. So cache it!
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cacheAtom(xu, name, reply.Atom)
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return reply.Atom, nil
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}
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// AtomName fetches a string representation of an ATOM given its integer id.
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func AtomName(xu *xgbutil.XUtil, aid xproto.Atom) (string, error) {
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// Check the cache first
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if atomName, ok := atomNameGet(xu, aid); ok {
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return string(atomName), nil
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}
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reply, err := xproto.GetAtomName(xu.Conn(), aid).Reply()
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if err != nil {
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return "", fmt.Errorf("AtomName: Error fetching name for ATOM "+
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"id '%d': %s", aid, err)
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}
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// If we're here, it means we didn't have ths ATOM id cached. So cache it.
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atomName := string(reply.Name)
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cacheAtom(xu, atomName, aid)
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return atomName, nil
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}
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// atomGet retrieves an atom identifier from a cache if it exists.
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func atomGet(xu *xgbutil.XUtil, name string) (xproto.Atom, bool) {
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xu.AtomsLck.RLock()
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defer xu.AtomsLck.RUnlock()
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aid, ok := xu.Atoms[name]
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return aid, ok
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}
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// atomNameGet retrieves an atom name from a cache if it exists.
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func atomNameGet(xu *xgbutil.XUtil, aid xproto.Atom) (string, bool) {
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xu.AtomNamesLck.RLock()
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defer xu.AtomNamesLck.RUnlock()
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name, ok := xu.AtomNames[aid]
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return name, ok
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}
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// cacheAtom puts an atom into the cache.
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func cacheAtom(xu *xgbutil.XUtil, name string, aid xproto.Atom) {
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xu.AtomsLck.Lock()
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xu.AtomNamesLck.Lock()
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defer xu.AtomsLck.Unlock()
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defer xu.AtomNamesLck.Unlock()
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xu.Atoms[name] = aid
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xu.AtomNames[aid] = name
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}
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