dmenu/dwm patch: color gradient

dwm_dmenu_color_gradient.patch

From 94132cbde161398b51cded896aa5989d0a96e563 Mon Sep 17 00:00:00 2001
From: NRK <nrk@disroot.org>
Date: Sat, 26 Mar 2022 03:06:36 +0600
Subject: [PATCH] patch: add color gradient

this patch uses HSL color representation and changes the hue +1 for each
w pixel. probably not very efficient drawing things one column at a time.

caveat: assumes true-color X server which supports rgb colors.
---
 drw.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 2 deletions(-)

diff --git a/drw.c b/drw.c
index a50c9ee..850a1d0 100644
--- a/drw.c
+++ b/drw.c
@@ -4,6 +4,7 @@
 #include <string.h>
 #include <X11/Xlib.h>
 #include <X11/Xft/Xft.h>
+#include <limits.h>
 
 #include "drw.h"
 #include "util.h"
@@ -16,6 +17,32 @@ static const unsigned char utfmask[UTF_SIZ + 1] = {0xC0, 0x80, 0xE0, 0xF0, 0xF8}
 static const long utfmin[UTF_SIZ + 1] = {       0,    0,  0x80,  0x800,  0x10000};
 static const long utfmax[UTF_SIZ + 1] = {0x10FFFF, 0x7F, 0x7FF, 0xFFFF, 0x10FFFF};
 
+typedef unsigned short    ushort;
+typedef unsigned long     ulong;
+typedef unsigned int      uint;
+#if UINT_MAX == 4294967295UL
+	typedef signed   int     i32;
+	typedef unsigned int     u32;
+	#define U32_X_FMT "X"
+#elif ULONG_MAX == 4294967295UL
+	typedef signed   long    i32;
+	typedef unsigned long    u32;
+	#define U32_X_FMT "lX"
+#else
+	#error "32 bit not available"
+#endif
+
+#define R(X)             (((X) & 0xFF0000) >> 16)
+#define G(X)             (((X) & 0x00FF00) >>  8)
+#define B(X)             (((X) & 0x0000FF) >>  0)
+
+typedef struct {
+	ushort h   : 9;
+	ushort s   : 7;
+	ushort l   : 7;
+	ushort idx : 9;
+} HSL;
+
 static long
 utf8decodebyte(const char c, size_t *i)
 {
@@ -248,6 +275,49 @@ drw_rect(Drw *drw, int x, int y, unsigned int w, unsigned int h, int filled, int
 		XDrawRectangle(drw->dpy, drw->drawable, drw->gc, x, y, w - 1, h - 1);
 }
 
+static u32
+hsl_to_rgb(HSL col)
+{
+	ulong f, p, q, t;
+	ulong h, s, l;
+	ulong r, g, b;
+
+	if (col.s == 0) {
+		const u32 tmp = (col.l * 255) / 100;
+		return (tmp << 16) | (tmp << 8) | tmp;
+	}
+
+	h = (col.h * 1000) / 6;
+	s = col.s;
+	l = col.l;
+
+	f = (h % 10000) / 100;
+	p = l * (100 - s);
+	q = l * (100 - (s * f) / 100);
+	t = (l * (10000 - s * (100 - f))) / 100;
+
+	l *= 100; /* scaled up x10000 */
+
+	switch (h/10000) {
+	case 0:
+		r = l; g = t; b = p; break;
+	case 1:
+		r = q; g = l; b = p; break;
+	case 2:
+		r = p; g = l; b = t; break;
+	case 3:
+		r = p; g = q; b = l; break;
+	case 4:
+		r = t; g = p; b = l; break;
+	default:
+		r = l; g = p; b = q; break;
+	}
+
+	return (((r * 255) / 10000) << 16) |
+	       (((g * 255) / 10000) <<  8) |
+	       (((b * 255) / 10000) <<  0);
+}
+
 int
 drw_text(Drw *drw, int x, int y, unsigned int w, unsigned int h, unsigned int lpad, const char *text, int invert)
 {
@@ -273,8 +343,14 @@ drw_text(Drw *drw, int x, int y, unsigned int w, unsigned int h, unsigned int lp
 	if (!render) {
 		w = invert ? invert : ~invert;
 	} else {
-		XSetForeground(drw->dpy, drw->gc, drw->scheme[invert ? ColFg : ColBg].pixel);
-		XFillRectangle(drw->dpy, drw->drawable, drw->gc, x, y, w, h);
+		static HSL col = { 0, 50, 50, 0 };
+		if (x < 10)
+			col.h = 0;
+		for (i = 0; i < w; ++i) {
+			col.h = (col.h + 1) % 360;
+			XSetForeground(drw->dpy, drw->gc, hsl_to_rgb(col));
+			XFillRectangle(drw->dpy, drw->drawable, drw->gc, x+i, y, 1, h);
+		}
 		d = XftDrawCreate(drw->dpy, drw->drawable,
 		                  DefaultVisual(drw->dpy, drw->screen),
 		                  DefaultColormap(drw->dpy, drw->screen));
-- 
2.34.1