st/st.h
bakkeby 5c7d8ab1ad auto-sync: draw on idle to avoid flicker/tearing
st could easily tear/flicker with animation or other unattended
output. This commit eliminates most of the tear/flicker.

Before this commit, the display timing had two "modes":

- Interactively, st was waiting fixed `1000/xfps` ms after forwarding
  the kb/mouse event to the application and before drawing.

- Unattended, and specifically with animations, the draw frequency was
  throttled to `actionfps`. Animation at a higher rate would throttle
  and likely tear, and at lower rates it was tearing big frames
  (specifically, when one `read` didn't get a full "frame").

The interactive behavior was decent, but it was impossible to get good
unattended-draw behavior even with carefully chosen configuration.

This commit changes the behavior such that it draws on idle instead of
using fixed latency/frequency. This means that it tries to draw only
when it's very likely that the application has completed its output
(or after some duration without idle), so it mostly succeeds to avoid
tear, flicker, and partial drawing.

The config values minlatency/maxlatency replace xfps/actionfps and
define the range which the algorithm is allowed to wait from the
initial draw-trigger until the actual draw. The range enables the
flexibility to choose when to draw - when least likely to flicker.

It also unifies the interactive and unattended behavior and config
values, which makes the code simpler as well - without sacrificing
latency during interactive use, because typically interactively idle
arrives very quickly, so the wait is typically minlatency.

While it only slighly improves interactive behavior, for animations
and other unattended-drawing it improves greatly, as it effectively
adapts to any [animation] output rate without tearing, throttling,
redundant drawing, or unnecessary delays (sounds impossible, but it
works).
2020-05-20 14:15:57 +02:00

148 lines
3.5 KiB
C

/* See LICENSE for license details. */
#include <stdint.h>
#include <sys/types.h>
#include "patches.h"
/* macros */
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) < (b) ? (b) : (a))
#define LEN(a) (sizeof(a) / sizeof(a)[0])
#define BETWEEN(x, a, b) ((a) <= (x) && (x) <= (b))
#define DIVCEIL(n, d) (((n) + ((d) - 1)) / (d))
#define DEFAULT(a, b) (a) = (a) ? (a) : (b)
#define LIMIT(x, a, b) (x) = (x) < (a) ? (a) : (x) > (b) ? (b) : (x)
#define ATTRCMP(a, b) ((a).mode != (b).mode || (a).fg != (b).fg || \
(a).bg != (b).bg)
#define TIMEDIFF(t1, t2) ((t1.tv_sec-t2.tv_sec)*1000 + \
(t1.tv_nsec-t2.tv_nsec)/1E6)
#define MODBIT(x, set, bit) ((set) ? ((x) |= (bit)) : ((x) &= ~(bit)))
#define TRUECOLOR(r,g,b) (1 << 24 | (r) << 16 | (g) << 8 | (b))
#define IS_TRUECOL(x) (1 << 24 & (x))
enum glyph_attribute {
ATTR_NULL = 0,
ATTR_BOLD = 1 << 0,
ATTR_FAINT = 1 << 1,
ATTR_ITALIC = 1 << 2,
ATTR_UNDERLINE = 1 << 3,
ATTR_BLINK = 1 << 4,
ATTR_REVERSE = 1 << 5,
ATTR_INVISIBLE = 1 << 6,
ATTR_STRUCK = 1 << 7,
ATTR_WRAP = 1 << 8,
ATTR_WIDE = 1 << 9,
ATTR_WDUMMY = 1 << 10,
#if BOXDRAW_PATCH
ATTR_BOXDRAW = 1 << 11,
#endif // BOXDRAW_PATCH
ATTR_BOLD_FAINT = ATTR_BOLD | ATTR_FAINT,
};
enum selection_mode {
SEL_IDLE = 0,
SEL_EMPTY = 1,
SEL_READY = 2
};
enum selection_type {
SEL_REGULAR = 1,
SEL_RECTANGULAR = 2
};
enum selection_snap {
SNAP_WORD = 1,
SNAP_LINE = 2
};
typedef unsigned char uchar;
typedef unsigned int uint;
typedef unsigned long ulong;
typedef unsigned short ushort;
typedef uint_least32_t Rune;
#define Glyph Glyph_
typedef struct {
Rune u; /* character code */
ushort mode; /* attribute flags */
uint32_t fg; /* foreground */
uint32_t bg; /* background */
} Glyph;
typedef Glyph *Line;
typedef union {
int i;
uint ui;
float f;
const void *v;
const char *s;
} Arg;
void die(const char *, ...);
void redraw(void);
void draw(void);
void printscreen(const Arg *);
void printsel(const Arg *);
void sendbreak(const Arg *);
void toggleprinter(const Arg *);
int tattrset(int);
void tnew(int, int);
void tresize(int, int);
void tsetdirtattr(int);
void ttyhangup(void);
int ttynew(char *, char *, char *, char **);
size_t ttyread(void);
void ttyresize(int, int);
void ttywrite(const char *, size_t, int);
void resettitle(void);
void selclear(void);
void selinit(void);
void selstart(int, int, int);
void selextend(int, int, int, int);
int selected(int, int);
char *getsel(void);
size_t utf8encode(Rune, char *);
void *xmalloc(size_t);
void *xrealloc(void *, size_t);
char *xstrdup(char *);
#if BOXDRAW_PATCH
int isboxdraw(Rune);
ushort boxdrawindex(const Glyph *);
#ifdef XFT_VERSION
/* only exposed to x.c, otherwise we'll need Xft.h for the types */
void boxdraw_xinit(Display *, Colormap, XftDraw *, Visual *);
void drawboxes(int, int, int, int, XftColor *, XftColor *, const XftGlyphFontSpec *, int);
#endif // XFT_VERSION
#endif // BOXDRAW_PATCH
#if RELATIVEBORDER_PATCH
int borderpx;
#endif // RELATIVEBORDER_PATCH
/* config.h globals */
extern char *utmp;
extern char *scroll;
extern char *stty_args;
extern char *vtiden;
extern wchar_t *worddelimiters;
extern int allowaltscreen;
extern char *termname;
extern unsigned int tabspaces;
extern unsigned int defaultfg;
extern unsigned int defaultbg;
extern unsigned int defaultcs;
#if BOXDRAW_PATCH
extern const int boxdraw, boxdraw_bold, boxdraw_braille;
#endif // BOXDRAW_PATCH
#if ALPHA_PATCH
extern float alpha;
#endif // ALPHA_PATCH