From 22f60d50ac323f29d2c56deef50a8a62e8677438 Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Mon, 21 Aug 2023 10:01:59 +0300
Subject: [PATCH] ref: gl: only enable/disable texture units in fixed-function
 pipeline rendering, in our case, low TMUs

---
 ref/gl/gl_backend.c | 26 +++++++++++++++++++++++---
 ref/gl/gl_image.c   |  5 ++---
 ref/gl/gl_local.h   |  1 +
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/ref/gl/gl_backend.c b/ref/gl/gl_backend.c
index 9d595d20..1ca0b440 100644
--- a/ref/gl/gl_backend.c
+++ b/ref/gl/gl_backend.c
@@ -259,6 +259,27 @@ void GL_MultiTexCoord2f( GLenum texture, GLfloat s, GLfloat t )
 		pglMultiTexCoord2f( texture + GL_TEXTURE0_ARB, s, t );
 }
 
+/*
+====================
+GL_EnableTextureUnit
+====================
+*/
+void GL_EnableTextureUnit( int tmu, qboolean enable )
+{
+	// only enable fixed-function pipeline units
+	if( tmu < glConfig.max_texture_units )
+	{
+		if( enable )
+		{
+			pglEnable( glState.currentTextureTargets[tmu] );
+		}
+		else if( glState.currentTextureTargets[tmu] != GL_NONE )
+		{
+			pglDisable( glState.currentTextureTargets[tmu] );
+		}
+	}
+}
+
 /*
 =================
 GL_TextureTarget
@@ -274,11 +295,10 @@ void GL_TextureTarget( uint target )
 
 	if( glState.currentTextureTargets[glState.activeTMU] != target )
 	{
-		if( glState.currentTextureTargets[glState.activeTMU] != GL_NONE )
-			pglDisable( glState.currentTextureTargets[glState.activeTMU] );
+		GL_EnableTextureUnit( glState.activeTMU, false );
 		glState.currentTextureTargets[glState.activeTMU] = target;
 		if( target != GL_NONE )
-			pglEnable( glState.currentTextureTargets[glState.activeTMU] );
+			GL_EnableTextureUnit( glState.activeTMU, true );
 	}
 }
 
diff --git a/ref/gl/gl_image.c b/ref/gl/gl_image.c
index 606ec891..737ba49f 100644
--- a/ref/gl/gl_image.c
+++ b/ref/gl/gl_image.c
@@ -105,10 +105,9 @@ void GL_Bind( GLint tmu, GLenum texnum )
 
 	if( glState.currentTextureTargets[tmu] != glTarget )
 	{
-		if( glState.currentTextureTargets[tmu] != GL_NONE )
-			pglDisable( glState.currentTextureTargets[tmu] );
+		GL_EnableTextureUnit( tmu, false );
 		glState.currentTextureTargets[tmu] = glTarget;
-		pglEnable( glState.currentTextureTargets[tmu] );
+		GL_EnableTextureUnit( tmu, true );
 	}
 
 	if( glState.currentTextures[tmu] == texture->texnum )
diff --git a/ref/gl/gl_local.h b/ref/gl/gl_local.h
index 5d940c87..f53f4561 100644
--- a/ref/gl/gl_local.h
+++ b/ref/gl/gl_local.h
@@ -301,6 +301,7 @@ void GL_CleanupAllTextureUnits( void );
 void GL_LoadIdentityTexMatrix( void );
 void GL_DisableAllTexGens( void );
 void GL_SetRenderMode( int mode );
+void GL_EnableTextureUnit( int tmu, qboolean enable );
 void GL_TextureTarget( uint target );
 void GL_Cull( GLenum cull );
 void R_ShowTextures( void );