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Improved font caching 

I made a patch that improves the performance of font caching mechanism.
This is based on a funny behaviour of FontConfig: it was handling
FcCharSet in a somewhat unexpected way.

So, we are currently adding "a character" to a new FcCharSet, and then
add it to a FcPattern. However, if we toss the FcPattern to FontConfig,
it loads the entire language(charset) that contains the character we
gave. That is, we don't always have to load a new font for each unknown
character. Instead, we can reused cached fonts, and this significantly
reduces the number of calls to extremely slow FontConfig matching
functions.

One more thing. I found that, in libXft, there's a function called
XftCharExists. XftCharIndex internally calls this function, and
does more stuffs if the character does exist. Since the returned index
is never used in st, we should call XftCharExists instead of
XftCharIndex. Please note that I already made this change in the patch.
This commit is contained in:
Eon S. Jeon 2013-07-19 01:07:02 -04:00 committed by Roberto E. Vargas Caballero
parent 40e4d76d22
commit 33ad83d492
1 changed files with 22 additions and 41 deletions
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63
st.c
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@ -462,17 +462,12 @@ enum {
typedef struct { typedef struct {
XftFont *font; XftFont *font;
long c;
int flags; int flags;
} Fontcache; } Fontcache;
/* /* Fontcache is an array now. A new font will be appended to the array. */
* Fontcache is a ring buffer, with frccur as current position and frclen as static Fontcache frc[16];
* the current length of used elements. static int frclen = 0;
*/
static Fontcache frc[1024];
static int frccur = -1, frclen = 0;
ssize_t ssize_t
xwrite(int fd, char *s, size_t len) { xwrite(int fd, char *s, size_t len) {
@ -2781,18 +2776,12 @@ xunloadfont(Font *f) {
void void
xunloadfonts(void) { xunloadfonts(void) {
int i, ip; int i;
/* /* Free the loaded fonts in the font cache. */
* Free the loaded fonts in the font cache. This is done backwards for(i = 0; i < frclen; i++) {
* from the frccur. XftFontClose(xw.dpy, frc[i].font);
*/
for(i = 0, ip = frccur; i < frclen; i++, ip--) {
if(ip < 0)
ip = LEN(frc) - 1;
XftFontClose(xw.dpy, frc[ip].font);
} }
frccur = -1;
frclen = 0; frclen = 0;
xunloadfont(&dc.font); xunloadfont(&dc.font);
@ -2918,7 +2907,7 @@ void
xdraws(char *s, Glyph base, int x, int y, int charlen, int bytelen) { xdraws(char *s, Glyph base, int x, int y, int charlen, int bytelen) {
int winx = borderpx + x * xw.cw, winy = borderpx + y * xw.ch, int winx = borderpx + x * xw.cw, winy = borderpx + y * xw.ch,
width = charlen * xw.cw, xp, i; width = charlen * xw.cw, xp, i;
int frp, frcflags; int frcflags;
int u8fl, u8fblen, u8cblen, doesexist; int u8fl, u8fblen, u8cblen, doesexist;
char *u8c, *u8fs; char *u8c, *u8fs;
long u8char; long u8char;
@ -3044,7 +3033,7 @@ xdraws(char *s, Glyph base, int x, int y, int charlen, int bytelen) {
s += u8cblen; s += u8cblen;
bytelen -= u8cblen; bytelen -= u8cblen;
doesexist = XftCharIndex(xw.dpy, font->match, u8char); doesexist = XftCharExists(xw.dpy, font->match, u8char);
if(!doesexist || bytelen <= 0) { if(!doesexist || bytelen <= 0) {
if(bytelen <= 0) { if(bytelen <= 0) {
if(doesexist) { if(doesexist) {
@ -3071,14 +3060,10 @@ xdraws(char *s, Glyph base, int x, int y, int charlen, int bytelen) {
if(doesexist) if(doesexist)
break; break;
frp = frccur;
/* Search the font cache. */ /* Search the font cache. */
for(i = 0; i < frclen; i++, frp--) { for(i = 0; i < frclen; i++) {
if(frp <= 0) if(XftCharExists(xw.dpy, frc[i].font, u8char)
frp = LEN(frc) - 1; && frc[i].flags == frcflags) {
if(frc[frp].c == u8char
&& frc[frp].flags == frcflags) {
break; break;
} }
} }
@ -3113,28 +3098,24 @@ xdraws(char *s, Glyph base, int x, int y, int charlen, int bytelen) {
/* /*
* Overwrite or create the new cache entry. * Overwrite or create the new cache entry.
*/ */
frccur++; if(frclen >= LEN(frc)) {
frclen++; frclen = LEN(frc) - 1;
if(frccur >= LEN(frc)) XftFontClose(xw.dpy, frc[frclen].font);
frccur = 0;
if(frclen > LEN(frc)) {
frclen = LEN(frc);
XftFontClose(xw.dpy, frc[frccur].font);
} }
frc[frccur].font = XftFontOpenPattern(xw.dpy, frc[frclen].font = XftFontOpenPattern(xw.dpy,
fontpattern); fontpattern);
frc[frccur].c = u8char; frc[frclen].flags = frcflags;
frc[frccur].flags = frcflags;
i = frclen;
frclen++;
FcPatternDestroy(fcpattern); FcPatternDestroy(fcpattern);
FcCharSetDestroy(fccharset); FcCharSetDestroy(fccharset);
frp = frccur;
} }
XftDrawStringUtf8(xw.draw, fg, frc[frp].font, XftDrawStringUtf8(xw.draw, fg, frc[i].font,
xp, winy + frc[frp].font->ascent, xp, winy + frc[i].font->ascent,
(FcChar8 *)u8c, u8cblen); (FcChar8 *)u8c, u8cblen);
xp += font->width; xp += font->width;