Added the force redraw on keypress patch

README.md

@@ -1,4 +1,4 @@
-Similar to [dwm-flexipatch](https://github.com/bakkeby/dwm-flexipatch) this st 0.8.2 (51e19ea11dd42eefed1ca136ee3f6be975f618b1, 2020-02-18) project has a different take on st patching. It uses preprocessor directives to decide whether or not to include a patch during build time. Essentially this means that this build, for better or worse, contains both the patched _and_ the original code. The aim being that you can select which patches to include and the build will contain that code and nothing more.
+Similar to [dwm-flexipatch](https://github.com/bakkeby/dwm-flexipatch) this st 0.8.2 (c279f5, 2020-04-19) project has a different take on st patching. It uses preprocessor directives to decide whether or not to include a patch during build time. Essentially this means that this build, for better or worse, contains both the patched _and_ the original code. The aim being that you can select which patches to include and the build will contain that code and nothing more.
 
 For example to include the `alpha` patch then you would only need to flip this setting from 0 to 1 in [patches.h](https://github.com/bakkeby/st-flexipatch/blob/master/patches.def.h):
 ```c
@@ -15,6 +15,8 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
 
 ### Changelog:
 
+2020-04-20 - Added the force redraw on pselect after key is pressed patch
+
 2020-03-29 - Added invert and workingdir patches
 
 2020-03-24 - Upgraded to latest (master) of st (commit 51e19ea11dd42eefed1ca136ee3f6be975f618b1 at the time of writing). Custom changes to make the altscreen mouse scollback patch working.
@@ -68,6 +70,9 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
    - [font2](https://st.suckless.org/patches/font2/)
       - allows you to add a spare font besides the default
 
+   - [force-redraw-after-keypress](https://lists.suckless.org/hackers/2004/17221.html)
+      - this patch forces the terminal to check for new data on the tty on keypress with the aim of reducing input latency
+
    - [hidecursor](https://st.suckless.org/patches/hidecursor/)
       - hides the X cursor whenever a key is pressed and show it back when the mouse is moved in the terminal window
 

patches.def.h

@@ -82,6 +82,15 @@
  */
 #define FONT2_PATCH 0
 
+/* This patch creates a global flag which is set when a keypress is sent
+ * from X which forces the terminal to check for new data on the tty fd on
+ * every return from pselect(). When new data read from the tty results in
+ * a line being redrawn, the flag is reset. This results in a less input lag
+ * when typing on the terminal.
+ * https://lists.suckless.org/hackers/2004/17221.html
+ */
+#define FORCE_REDRAW_AFTER_KEYPRESS 0
+
 /* Hide the X cursor whenever a key is pressed and show it back when the mouse is moved in
  * the terminal window.
  * https://st.suckless.org/patches/hidecursor/

x.c

@@ -251,6 +251,9 @@ static DC dc;
 static XWindow xw;
 static XSelection xsel;
 static TermWindow win;
+#if FORCE_REDRAW_AFTER_KEYPRESS
+static int pendingkpress = 0;
+#endif // FORCE_REDRAW_AFTER_KEYPRESS
 
 /* Font Ring Cache */
 enum {
@@ -935,6 +938,12 @@ xclear(int x1, int y1, int x2, int y2)
 	#endif // INVERT_PATCH
 }
 
+void
+xclearwin(void)
+{
+	xclear(0, 0, win.w, win.h);
+}
+
 void
 xhints(void)
 {
@@ -1937,6 +1946,10 @@ xdrawline(Line line, int x1, int y1, int x2)
 	Glyph base, new;
 	XftGlyphFontSpec *specs = xw.specbuf;
 
+	#if FORCE_REDRAW_AFTER_KEYPRESS
+	pendingkpress = 0;
+	#endif // FORCE_REDRAW_AFTER_KEYPRESS
+
 	numspecs = xmakeglyphfontspecs(specs, &line[x1], x2 - x1, x1, y1);
 	i = ox = 0;
 	for (x = x1; x < x2 && i < numspecs; x++) {
@@ -2168,6 +2181,10 @@ kpress(XEvent *ev)
 	Status status;
 	Shortcut *bp;
 
+	#if FORCE_REDRAW_AFTER_KEYPRESS
+	pendingkpress = 1;
+	#endif // FORCE_REDRAW_AFTER_KEYPRESS
+
 	#if HIDECURSOR_PATCH
 	if (xw.pointerisvisible) {
 		XDefineCursor(xw.dpy, xw.win, xw.bpointer);
@@ -2330,6 +2347,10 @@ run(void)
 		tv = &drawtimeout;
 
 		dodraw = 0;
+		#if FORCE_REDRAW_AFTER_KEYPRESS
+		if (pendingkpress)
+			dodraw = 1;
+		#endif // FORCE_REDRAW_AFTER_KEYPRESS
 		#if VISUALBELL_2_PATCH || VISUALBELL_3_PATCH
 		to_ms = -1; /* timeout in ms, indefinite if negative */
 		if (blinkset) {