# st

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    commit 896310e5928b6daab5f594acd9648ffe8233022e
    parent 13a8eeb810ccfdaefd58c52328dd0ec867e3ae8d
    Author: Aurélien Aptel <aurelien.aptel@gmail.com>
    Date:   Sat, 21 Jan 2012 23:14:41 +0100

    copy dirty lines to screen, add select() timeout & min time between draw() calls.

    * add a timeout value (SELECT_TIMEOUT) of 20ms in the select() call
    * wait at least 20ms (DRAW_TIMEOUT) between draw() calls
    * only copy dirty lines from the buffer to the screen

    what draw() does:
    * clears dirty lines in the buffer
    * draws the longest same-attributes string of each
      dirty line to the buffer with multiple xdraws() call
    * copies the current dirty line from buffer to the screen with a single
      xcopy() call

    this changeset makes st run ~10x faster.
    Diffstat:
    Mst.c | 53++++++++++++++++++++++++++++++++++++++++++++---------

    1 file changed, 44 insertions(+), 9 deletions(-)
    diff --git a/st.c b/st.c
    @@ -13,8 +13,10 @@
     #include <sys/ioctl.h>
     #include <sys/select.h>
     #include <sys/stat.h>
    +#include <sys/time.h>
     #include <sys/types.h>
     #include <sys/wait.h>
    +#include <time.h>
     #include <unistd.h>
     #include <X11/Xatom.h>
     #include <X11/Xlib.h>
    @@ -22,9 +24,6 @@
     #include <X11/cursorfont.h>
     #include <X11/keysym.h>

    -#include <sys/time.h>
    -#include <time.h>
    -
     #if   defined(__linux)
      #include <pty.h>
     #elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__APPLE__)
    @@ -50,6 +49,9 @@
     #define XK_NO_MOD     UINT_MAX
     #define XK_ANY_MOD    0

    +#define SELECT_TIMEOUT (20*1000) /* 20 ms */
    +#define DRAW_TIMEOUT  (20*1000) /* 20 ms */
    +
     #define SERRNO strerror(errno)
     #define MIN(a, b)  ((a) < (b) ? (a) : (b))
     #define MAX(a, b)  ((a) < (b) ? (b) : (a))
    @@ -138,6 +140,7 @@ typedef struct {
     	int ch; /* char height */
     	int cw; /* char width  */
     	char state; /* focus, redraw, visible */
    +	struct timeval lastdraw;
     } XWindow;

     typedef struct {
    @@ -179,6 +182,7 @@ static void drawregion(int, int, int, int);
     static void execsh(void);
     static void sigchld(int);
     static void run(void);
    +static int last_draw_too_old(void);

     static void csidump(void);
     static void csihandle(void);
    @@ -214,6 +218,7 @@ static void ttywrite(const char *, size_t);
     static void xdraws(char *, Glyph, int, int, int, int);
     static void xhints(void);
     static void xclear(int, int, int, int);
    +static void xcopy(int, int, int, int);
     static void xdrawcursor(void);
     static void xinit(void);
     static void xloadcols(void);
    @@ -224,7 +229,7 @@ static void xresize(int, int);
     static void expose(XEvent *);
     static void visibility(XEvent *);
     static void unmap(XEvent *);
    -static char* kmap(KeySym, unsigned int state);
    +static char* kmap(KeySym, unsigned int);
     static void kpress(XEvent *);
     static void cmessage(XEvent *);
     static void resize(XEvent *);
    @@ -1786,6 +1791,14 @@ xdraws(char *s, Glyph base, int x, int y, int charlen, int bytelen) {
     		XDrawLine(xw.dpy, xw.buf, dc.gc, winx, winy+1, winx+width-1, winy+1);
     }

    +/* copy buffer pixmap to screen pixmap */
    +void
    +xcopy(int x, int y, int cols, int rows) {
    +	int src_x = x*xw.cw, src_y = y*xw.ch, src_w = cols*xw.cw, src_h = rows*xw.ch;
    +	int dst_x = BORDER+src_x, dst_y = BORDER+src_y;
    +	XCopyArea(xw.dpy, xw.buf, xw.win, dc.gc, src_x, src_y, src_w, src_h, dst_x, dst_y);
    +}
    +
     void
     xdrawcursor(void) {
     	static int oldx = 0;
    @@ -1805,7 +1818,9 @@ xdrawcursor(void) {
     		xdraws(term.line[oldy][oldx].c, term.line[oldy][oldx], oldx, oldy, 1, sl);
     	} else
     		xclear(oldx, oldy, oldx, oldy);
    -
    +
    +	xcopy(oldx, oldy, 1, 1);
    +
     	/* draw the new one */
     	if(!(term.c.state & CURSOR_HIDE) && (xw.state & WIN_FOCUSED)) {
     		sl = utf8size(g.c);
    @@ -1814,11 +1829,14 @@ xdrawcursor(void) {
     		xdraws(g.c, g, term.c.x, term.c.y, 1, sl);
     		oldx = term.c.x, oldy = term.c.y;
     	}
    +
    +	xcopy(term.c.x, term.c.y, 1, 1);
     }

     void
     draw() {
     	drawregion(0, 0, term.col, term.row);
    +	gettimeofday(&xw.lastdraw, NULL);
     }

     void
    @@ -1859,9 +1877,9 @@ drawregion(int x1, int y1, int x2, int y2) {
     		}
     		if(ib > 0)
     			xdraws(buf, base, ox, y, ic, ib);
    +		xcopy(0, y, term.col, 1);
     	}
     	xdrawcursor();
    -	XCopyArea(xw.dpy, xw.buf, xw.win, dc.gc, x1*xw.cw, y1*xw.ch, x2*xw.cw, y2*xw.ch, BORDER, BORDER);
     }

     void
    @@ -2006,25 +2024,42 @@ resize(XEvent *e) {
     	xresize(col, row);
     }

    +int
    +last_draw_too_old(void) {
    +	struct timeval now;
    +	gettimeofday(&now, NULL);
    +	return TIMEDIFF(now, xw.lastdraw) >= PRINT_TIMEOUT/1000;
    +}
    +
     void
     run(void) {
     	XEvent ev;
     	fd_set rfd;
     	int xfd = XConnectionNumber(xw.dpy);
    -
    +	struct timeval timeout = {0};
    +	int stuff_to_print = 0;
    +
     	for(;;) {
     		FD_ZERO(&rfd);
     		FD_SET(cmdfd, &rfd);
     		FD_SET(xfd, &rfd);
    -		if(select(MAX(xfd, cmdfd)+1, &rfd, NULL, NULL, NULL) < 0) {
    +		timeout.tv_sec  = 0;
    +		timeout.tv_usec = SELECT_TIMEOUT;
    +		if(select(MAX(xfd, cmdfd)+1, &rfd, NULL, NULL, &timeout) < 0) {
     			if(errno == EINTR)
     				continue;
     			die("select failed: %s\n", SERRNO);
     		}
     		if(FD_ISSET(cmdfd, &rfd)) {
     			ttyread();
    +			stuff_to_print = 1;
    +		}
    +
    +		if(stuff_to_print && last_draw_too_old()) {
    +			stuff_to_print = 0;
     			draw();
     		}
    +
     		while(XPending(xw.dpy)) {
     			XNextEvent(xw.dpy, &ev);
     			if(XFilterEvent(&ev, xw.win))
    @@ -2050,7 +2085,7 @@ main(int argc, char *argv[]) {
     		case 'w':
     			if(++i < argc) opt_embed = argv[i];
     			break;
    -		case 'e':
    +		case 'e':
     			/* eat every remaining arguments */
     			if(++i < argc) opt_cmd = &argv[i];
     			goto run;