From 0fe6827daeb52d9de900204bf59c305d23155425 Mon Sep 17 00:00:00 2001
From: Zughy <63455151+Zughy@users.noreply.github.com>
Date: Sat, 20 Dec 2025 15:14:08 +0100
Subject: [PATCH] Add alpha channel in HUD text elements (#16730)

---
 doc/lua_api.md     |  7 +++++--
 src/client/hud.cpp | 13 ++++++++++---
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/doc/lua_api.md b/doc/lua_api.md
index 03bd1d692..c0418fabf 100644
--- a/doc/lua_api.md
+++ b/doc/lua_api.md
@@ -1851,8 +1851,11 @@ Displays text on the HUD.
 * `text`: The text to be displayed in the HUD element.
   Supports `core.translate` (always)
   and `core.colorize` (since protocol version 44)
-* `number`: An integer containing the RGB value of the color used to draw the
-  text. Specify `0xFFFFFF` for white text, `0xFF0000` for red, and so on.
+* `number`: An integer containing the (A)RGB value of the color used to draw the
+  text. Specify `0xFFFFFF` for white text, `0x80FF0000` for semi-transparent red, and so on.
+    * Alpha only works on Luanti 5.15+ clients. Older clients will see the text as opaque.
+    * To completely hide a text, set `text` to `""`. Setting the alpha value to `00`
+      will not work due to compatibility reasons (it'll be treated as `FF`).
 * `alignment`: The alignment of the text.
 * `offset`: offset in pixels from position.
 * `size`: size of the text.
diff --git a/src/client/hud.cpp b/src/client/hud.cpp
index 4155ce7cf..cffc3dba4 100644
--- a/src/client/hud.cpp
+++ b/src/client/hud.cpp
@@ -394,9 +394,16 @@ void Hud::drawLuaElements(const v3s16 &camera_offset)
 				if (textfont->getType() == gui::EGFT_CUSTOM)
 					ttfont = static_cast<gui::CGUITTFont *>(textfont);
 
-				video::SColor color(255, (e->number >> 16) & 0xFF,
-										 (e->number >> 8)  & 0xFF,
-										 (e->number >> 0)  & 0xFF);
+				u32 num = e->number;
+				u8 alpha = (num >> 24) & 0xFF;
+				if (alpha == 0)
+					alpha = 0xFF; // Backwards compatibility
+
+				video::SColor color = video::SColor(alpha,
+						(num >> 16) & 0xFF,
+						(num >> 8)  & 0xFF,
+						(num >> 0)  & 0xFF);
+
 				EnrichedString text(unescape_string(utf8_to_wide(e->text)), color);
 				core::dimension2d<u32> textsize = textfont->getDimension(text.c_str());