Added picom shader, fixing stalonetray transparency

picom/.config/picom/black_to_transparent.frag

@@ -0,0 +1,21 @@
+#version 330
+in vec2 texcoord;
+uniform float opacity;
+uniform bool invert_color;
+uniform sampler2D tex;
+
+vec4 window_shader() {
+	vec4 c = texelFetch(tex, ivec2(texcoord), 0);
+	{
+		// Change vec4(1.0, 1.0, 1.0, 1.0) to your desired color
+		vec4 vdiff = abs(vec4(0.0, 0.0, 0.0, 1.0) - c);
+		float diff = max(max(max(vdiff.r, vdiff.g), vdiff.b), vdiff.a);
+		// Change 0.8 to your desired opacity
+		if (diff < 0.001)
+			c *= 0;
+	}
+	if (invert_color)
+		c = vec4(vec3(c.a, c.a, c.a) - vec3(c), c.a);
+	c *= opacity;
+	return c;
+}

picom/.config/picom/picom.conf

@@ -294,6 +294,13 @@ use-damage = true;
 #
 # glx-fshader-win = ""
 
+# Use rules to set per-window shaders. Syntax is SHADER_PATH:PATTERN, similar
+# to opacity-rule. SHADER_PATH can be "default". This overrides window-shader-fg.
+#
+window-shader-fg-rule = [
+  "black_to_transparent.frag:class_g = 'stalonetray'"
+]
+
 # Force all windows to be painted with blending. Useful if you
 # have a glx-fshader-win that could turn opaque pixels transparent.
 #