From 965576f2c628f93babd5d54f5b9cd96be080d2e1 Mon Sep 17 00:00:00 2001
From: Alex Shvartzkop <dudesuchamazing@gmail.com>
Date: Sun, 31 Dec 2023 15:05:00 +0500
Subject: [PATCH] Enable alpha test for bitmaps in OpenGL GAL.

---
 common/gal/opengl/opengl_gal.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/common/gal/opengl/opengl_gal.cpp b/common/gal/opengl/opengl_gal.cpp
index 7cdfc20555..3bb06802e3 100644
--- a/common/gal/opengl/opengl_gal.cpp
+++ b/common/gal/opengl/opengl_gal.cpp
@@ -1492,6 +1492,9 @@ void OPENGL_GAL::DrawBitmap( const BITMAP_BASE& aBitmap, double alphaBlend )
 
     glDepthFunc( GL_ALWAYS );
 
+    glAlphaFunc( GL_GREATER, 0.01f );
+    glEnable( GL_ALPHA_TEST );
+
     glMatrixMode( GL_TEXTURE );
     glPushMatrix();
     glTranslated( 0.5, 0.5, 0.5 );
@@ -1538,6 +1541,8 @@ void OPENGL_GAL::DrawBitmap( const BITMAP_BASE& aBitmap, double alphaBlend )
     glPopMatrix();
     glMatrixMode( GL_MODELVIEW );
 
+    glDisable( GL_ALPHA_TEST );
+
     glDepthFunc( GL_LESS );
 }