config: add shadow-hex option

This allows the user to specify the shadow color via a single option,
instead of specifying red, green and blue separately.

man/picom.1.asciidoc

@@ -151,6 +151,9 @@ OPTIONS
 *--shadow-exclude* 'CONDITION'::
 	Specify a list of conditions of windows that should have no shadow.
 
+*--shadow-hex* 'STRING'::
+  Color of shadow using hex string ('#000000')
+
 *--fade-exclude* 'CONDITION'::
 	Specify a list of conditions of windows that should not be faded.
 

picom.sample.conf

@@ -44,6 +44,9 @@ shadow-offset-y = -7;
 # Blue color value of shadow (0.0 - 1.0, defaults to 0).
 # shadow-blue = 0
 
+# Hex string color value of shadow (#000000 - #FFFFFF, defaults to #000000). This option will override options set shadow-(red/green/blue)
+# shadow-hex = "#000000"
+
 # Do not paint shadows on shaped windows. Note shaped windows 
 # here means windows setting its shape through X Shape extension. 
 # Those using ARGB background is beyond our control. 

src/config.c

@@ -515,6 +515,7 @@ char *parse_config(options_t *opt, const char *config_file, bool *shadow_enable,
 	    .sw_opti = false,
 	    .use_damage = true,
 
+	    .shadow_hex = "#000000",
 	    .shadow_red = 0.0,
 	    .shadow_green = 0.0,
 	    .shadow_blue = 0.0,

src/config.h

@@ -140,6 +140,7 @@ typedef struct options {
 	// === Shadow ===
 	/// Red, green and blue tone of the shadow.
 	double shadow_red, shadow_green, shadow_blue;
+	char *shadow_hex;
 	int shadow_radius;
 	int shadow_offset_x, shadow_offset_y;
 	double shadow_opacity;

src/config_libconfig.c

@@ -21,6 +21,21 @@
 
 #pragma GCC diagnostic error "-Wunused-parameter"
 
+/**
+ * Hex color to rgb
+ */
+struct color hex_to_rgb(const char *hex) {
+	struct color rgb;
+	// Ignore the # in front of the string
+	const char *sane_hex = hex + 1;
+	int hex_color = (int)strtol(sane_hex, NULL, 16);
+	rgb.red = (float)(hex_color >> 16) / 256;
+	rgb.green = (float)((hex_color & 0x00ff00) >> 8) / 256;
+	rgb.blue = (float)(hex_color & 0x0000ff) / 256;
+
+	return rgb;
+}
+
 /**
  * Wrapper of libconfig's <code>config_lookup_int</code>.
  *
@@ -410,6 +425,14 @@ char *parse_config_libconfig(options_t *opt, const char *config_file, bool *shad
 	config_lookup_float(&cfg, "shadow-green", &opt->shadow_green);
 	// --shadow-blue
 	config_lookup_float(&cfg, "shadow-blue", &opt->shadow_blue);
+	// --shadow-hex
+	if (config_lookup_string(&cfg, "shadow-hex", &sval)) {
+		struct color rgb;
+		rgb = hex_to_rgb(sval);
+		opt->shadow_red = rgb.red;
+		opt->shadow_green = rgb.green;
+		opt->shadow_blue = rgb.blue;
+	}
 	// --shadow-exclude-reg
 	if (config_lookup_string(&cfg, "shadow-exclude-reg", &sval))
 		opt->shadow_exclude_reg_str = strdup(sval);