From 603eb579431bf366f8186ea5d11eb6f2f35f746f Mon Sep 17 00:00:00 2001
From: DS <ds.desour@proton.me>
Date: Fri, 16 Aug 2024 22:01:16 +0200
Subject: [PATCH] Fix comment and alpha test node oopsies from #14852

---
 games/devtest/mods/testnodes/textures.lua       |   8 +++++---
 .../testnodes_alpha_compositing_bottom.png      | Bin 251 -> 265 bytes
 src/client/imagesource.cpp                      |  12 +++++-------
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/games/devtest/mods/testnodes/textures.lua b/games/devtest/mods/testnodes/textures.lua
index 86bc3e343..96f291d6a 100644
--- a/games/devtest/mods/testnodes/textures.lua
+++ b/games/devtest/mods/testnodes/textures.lua
@@ -89,10 +89,12 @@ for a=1,#alphas do
 end
 
 minetest.register_node("testnodes:alpha_compositing", {
-	description = S("Alpha Compositing Test Node") .. "\n" ..
+	description = S("Texture Overlay Test Node") .. "\n" ..
 		S("A regular grid should be visible where each cell contains two " ..
-		"texels with the same colour.") .. "\n" ..
-		S("Alpha compositing is gamma-incorrect for backwards compatibility."),
+		"texels with the same color.") .. "\n" ..
+		S("Texture overlay is gamma-incorrect, " ..
+		"and in general it does not do alpha compositing, " ..
+		"both for backwards compatibility."),
 	drawtype = "glasslike",
 	paramtype = "light",
 	tiles = {"testnodes_alpha_compositing_bottom.png^"  ..
diff --git a/games/devtest/mods/testnodes/textures/testnodes_alpha_compositing_bottom.png b/games/devtest/mods/testnodes/textures/testnodes_alpha_compositing_bottom.png
index 83447e42309a9c7433a74662b39fb40175bb74a9..40d9f53dea9a98a249ba624c9a39f778ddc2bdd2 100644
GIT binary patch
delta 248
zcmey(*vT|OvYwfNfk8u;KNv{)1^9%x0%_6WY_Y=3d<ltSQPKYl|3ACz1`4hSKK}pz
z|MvFw&a^!3TT6f<3=IFZYi=3axSP+*%#xo~4+ISi4Gj&qBDMbm<$yZ>|8KGi%>gRp
zEeY}qW?*LK;&KTD8nI%<mL;6UW<ZJ9LQfaR5Q)oE``q~&9C(hj-DBp_{qujZj*hRO
zxZlP#Dn<+?84hz_Z<{~m0Hgjw?|BOqEW%QiLsqoA7x*$A@shkGFwy!U=XQoW*Zy_a
p)p6ce+~)kRe8t;<+l;phJ9)Vad0D$B#(RMr>*?y}vd$@?2>?*OT`~Xw

delta 234
zcmV<G02Tj<0{a1w8Gi-<001BJ|6u?C0K!Q`K~#9!V?YMRHtzqSOfa1#KkNVh{|x_c
zMQZ=ozO`hFcFnE-=JPWDH#9VW#ewn=^;i@TZ@_;L0@}DD_;@=|4+t{=W!qt<gXsDO
zhX0M(p~u&*U3(lP4N?I$9IP9w0-_CoFu-gV(c)}okfvf$QDZKs6Tyn>>+AnNo19bT
z;^M#tl6Q7>6oJbF36P&K6(9`2FAoDi0l1TqC1Gq_@)R3DFdYDyWTpdz0Yg0<0BOq7
k0g$FF9l*qJ$y00q0DfS@_D8%Q_y7O^07*qoM6N<$f(SBZ9{>OV

diff --git a/src/client/imagesource.cpp b/src/client/imagesource.cpp
index 696159408..adc39f130 100644
--- a/src/client/imagesource.cpp
+++ b/src/client/imagesource.cpp
@@ -371,14 +371,12 @@ void blitBaseImage(video::IImage* &src, video::IImage* &dst)
 
 namespace {
 
-/** Calculate the color of a single pixel drawn on top of another pixel without
- * gamma correction
+/** Calculate the result of the overlay texture modifier (`^`) for a single
+ * pixel
  *
- * The color mixing is a little more complicated than just
- * video::SColor::getInterpolated because getInterpolated does not handle alpha
- * correctly.
- * For example, a pixel with alpha=64 drawn atop a pixel with alpha=128 should
- * yield a pixel with alpha=160, while getInterpolated would yield alpha=96.
+ * This is not alpha blending if both src and dst are semi-transparent. The
+ * reason this is that an old implementation did it wrong, and fixing it would
+ * break backwards compatibility (see #14847).
  *
  * \tparam overlay If enabled, only modify dst_col if it is fully opaque
  * \param src_col Color of the top pixel