[hackers] [st][PATCH 1/3] Update XIM spot location when needed

[Ivan Tham]

Reduce number of calls to update XIM only if cursor position was changed
and user is not holding a key. In other words, send cursor position on
the last key release which change cursor position.

It also help reduce input lag problem with fcitx5 when holding keys.
---
 st.c |  7 +++++--
 x.c  | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/st.c b/st.c
index 3e48410..cb3a4dc 100644
--- a/st.c
+++ b/st.c
@@ -2570,7 +2570,7 @@ drawregion(int x1, int y1, int x2, int y2)
 void
 draw(void)
 {
-       int cx = term.c.x;
+       int cc, cx = term.c.x;
 
        if (!xstartdraw())
                return;
@@ -2586,9 +2586,12 @@ draw(void)
        drawregion(0, 0, term.col, term.row);
        xdrawcursor(cx, term.c.y, term.line[term.c.y][cx],
                        term.ocx, term.ocy, term.line[term.ocy][term.ocx]);
+       cc = term.ocx != cx || term.ocy != term.c.y;
        term.ocx = cx, term.ocy = term.c.y;
        xfinishdraw();
-       xximspot(term.ocx, term.ocy);
+
+       if (cc)
+               xximspot(term.ocx, term.ocy);
 }
 
 void
diff --git a/x.c b/x.c
index 1f62129..bf6d605 100644
--- a/x.c
+++ b/x.c
@@ -94,6 +94,7 @@ typedef struct {
        Drawable buf;
        GlyphFontSpec *specbuf; /* font spec buffer used for rendering */
        Atom xembed, wmdeletewin, netwmname, netwmpid;
+       XKeyEvent lkr; /* last key release event */
        struct {
                XIM xim;
                XIC xic;
@@ -107,6 +108,7 @@ typedef struct {
        int isfixed; /* is fixed geometry? */
        int l, t; /* left and top offset */
        int gm; /* geometry mask */
+       int repeat; /* key repeat */
 } XWindow;
 
 typedef struct {
@@ -168,6 +170,7 @@ static void expose(XEvent *);
 static void visibility(XEvent *);
 static void unmap(XEvent *);
 static void kpress(XEvent *);
+static void krelease(XEvent *);
 static void cmessage(XEvent *);
 static void resize(XEvent *);
 static void focus(XEvent *);
@@ -190,6 +193,7 @@ static void usage(void);
 
 static void (*handler[LASTEvent])(XEvent *) = {
        [KeyPress] = kpress,
+       [KeyRelease] = krelease,
        [ClientMessage] = cmessage,
        [ConfigureNotify] = resize,
        [VisibilityNotify] = visibility,
@@ -1627,7 +1631,7 @@ xfinishdraw(void)
 void
 xximspot(int x, int y)
 {
-       if (xw.ime.xic == NULL)
+       if (xw.ime.xic == NULL || xw.repeat)
                return;
 
        xw.ime.spot.x = borderpx + x * win.cw;
@@ -1782,6 +1786,9 @@ kpress(XEvent *ev)
        if (IS_SET(MODE_KBDLOCK))
                return;
 
+       /* keep track of repeat */
+       xw.repeat = xw.lkr.time == e->time && xw.lkr.keycode == e->keycode;
+
        if (xw.ime.xic)
                len = XmbLookupString(xw.ime.xic, e, buf, sizeof buf, &ksym, 
&status);
        else
@@ -1818,6 +1825,12 @@ kpress(XEvent *ev)
        ttywrite(buf, len, 1);
 }
 
+void
+krelease(XEvent *ev)
+{
+       xw.lkr = ev->xkey;
+}
+
 void
 cmessage(XEvent *e)
 {
-- 
2.25.0