Add support for additional alpha when the term-window is not focused

Xdefaults

@@ -1,5 +1,6 @@
 !! Transparency (0-1):
 st.alpha: 0.92
+st.alphaUnfocus: 0.62
 
 !! Set a default font and font size as below:
 st.font: Monospace-11;

config.h

@@ -108,6 +108,7 @@ unsigned int tabspaces = 8;
 
 /* bg opacity */
 float alpha = 0.8;
+float alphaUnfocus = 0.8;
 
 /* Terminal colors (16 first used in escape sequence) */
 static const char *colorname[] = {
@@ -144,6 +145,7 @@ unsigned int defaultfg = 259;
 unsigned int defaultbg = 258;
 unsigned int defaultcs = 256;
 unsigned int defaultrcs = 257;
+unsigned int background = 258;
 
 /*
  * Default shape of cursor
@@ -217,6 +219,7 @@ ResourcePref resources[] = {
 		{ "cwscale",      FLOAT,   &cwscale },
 		{ "chscale",      FLOAT,   &chscale },
 		{ "alpha",        FLOAT,   &alpha },
+		{ "alphaUnfocus", FLOAT,   &alphaUnfocus },
 };
 
 /*

st.c

@@ -201,7 +201,6 @@ static void tsetscroll(int, int);
 static void tswapscreen(void);
 static void tsetmode(int, int, int *, int);
 static int twrite(const char *, int, int);
-static void tfulldirt(void);
 static void tcontrolcode(uchar );
 static void tdectest(char );
 static void tdefutf8(char);

st.h

@@ -82,6 +82,7 @@ typedef union {
 
 void die(const char *, ...);
 void redraw(void);
+void tfulldirt(void);
 void draw(void);
 
 void externalpipe(const Arg *);
@@ -138,4 +139,5 @@ extern unsigned int tabspaces;
 extern unsigned int defaultfg;
 extern unsigned int defaultbg;
 extern float alpha;
+extern float alphaUnfocus;
 extern const int boxdraw, boxdraw_bold, boxdraw_braille;

x.c

@@ -272,6 +272,8 @@ static char *opt_line  = NULL;
 static char *opt_name  = NULL;
 static char *opt_title = NULL;
 
+static int focused = 0;
+
 static int oldbutton = 3; /* button event on startup: 3 = release */
 
 void
@@ -807,6 +809,16 @@ xloadcolor(int i, const char *name, Color *ncolor)
 	return XftColorAllocName(xw.dpy, xw.vis, xw.cmap, name, ncolor);
 }
 
+void
+xloadalpha(void)
+{
+	float const usedAlpha = focused ? alpha : alphaUnfocus;
+	if (opt_alpha) alpha = strtof(opt_alpha, NULL);
+	dc.col[defaultbg].color.alpha = (unsigned short)(0xffff * usedAlpha);
+	dc.col[defaultbg].pixel &= 0x00FFFFFF;
+	dc.col[defaultbg].pixel |= (unsigned char)(0xff * usedAlpha) << 24;
+}
+
 void
 xloadcols(void)
 {
@@ -814,15 +826,12 @@ xloadcols(void)
 	static int loaded;
 	Color *cp;
 
-	if (loaded) {
-		for (cp = dc.col; cp < &dc.col[dc.collen]; ++cp)
-			XftColorFree(xw.dpy, xw.vis, xw.cmap, cp);
-	} else {
-		dc.collen = MAX(LEN(colorname), 256);
+	if (!loaded) {
+		dc.collen = 1 + (defaultbg = MAX(LEN(colorname), 256));
 		dc.col = xmalloc(dc.collen * sizeof(Color));
 	}
 
-	for (i = 0; i < dc.collen; i++)
+	for (i = 0; i+1 < dc.collen; i++)
 		if (!xloadcolor(i, NULL, &dc.col[i])) {
 			if (colorname[i])
 				die("could not allocate color '%s'\n", colorname[i]);
@@ -830,12 +839,10 @@ xloadcols(void)
 				die("could not allocate color %d\n", i);
 		}
 
-	/* set alpha value of bg color */
-	if (opt_alpha)
-		alpha = strtof(opt_alpha, NULL);
-	dc.col[defaultbg].color.alpha = (unsigned short)(0xffff * alpha);
-	dc.col[defaultbg].pixel &= 0x00FFFFFF;
-	dc.col[defaultbg].pixel |= (unsigned char)(0xff * alpha) << 24;
+	if (dc.collen) // cannot die, as the color is already loaded.
+		xloadcolor(background, NULL, &dc.col[defaultbg]);
+
+	xloadalpha();
 	loaded = 1;
 }
 
@@ -1910,12 +1917,22 @@ focus(XEvent *ev)
 		xseturgency(0);
 		if (IS_SET(MODE_FOCUS))
 			ttywrite("\033[I", 3, 0);
+		if (!focused) {
+			focused = 1;
+			xloadcols();
+			tfulldirt();
+		}
 	} else {
 		if (xw.ime.xic)
 			XUnsetICFocus(xw.ime.xic);
 		win.mode &= ~MODE_FOCUSED;
 		if (IS_SET(MODE_FOCUS))
 			ttywrite("\033[O", 3, 0);
+		if (focused) {
+			focused = 0;
+			xloadcols();
+			tfulldirt();
+		}
 	}
 }
 
@@ -2280,6 +2297,7 @@ run:
 	config_init();
 	cols = MAX(cols, 1);
 	rows = MAX(rows, 1);
+	defaultbg = MAX(LEN(colorname), 256);
 	tnew(cols, rows);
 	xinit(cols, rows);
 	xsetenv();