From 721beb9202f2090c87ae391781f865d61a6f2b33 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 14 Jun 2019 11:11:43 +0530
Subject: [PATCH] More docs for the cell fragment shader

---
 kitty/cell_fragment.glsl | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kitty/cell_fragment.glsl b/kitty/cell_fragment.glsl
index ffc80fedd..aae9222f0 100644
--- a/kitty/cell_fragment.glsl
+++ b/kitty/cell_fragment.glsl
@@ -86,6 +86,9 @@ vec4 blend_onto_opaque_premul(vec3 over, float over_alpha, vec3 under) {
  *        First everything is rendered into a framebuffer, and then the framebauffer is blended onto
  *        the screen. The framebuffer is needed because it allows access to the background color pixels
  *        to blend with the image pixels. The steps are basically the same as for 2a.
+ *
+ *  In this shader exactly *one* of SIMPLE, SPECIAL, FOREGROUND or BACKGROUND will be defined, corresponding
+ *  to the appropriate rendering pass from above.
  */
 #ifdef NEEDS_FOREGROUND
 vec4 calculate_foreground() {