fixup: use glBindSampler()

Author: illwieckz

src/engine/renderer/tr_backend.cpp

@@ -1625,18 +1625,42 @@ void RB_FXAA()
 		GL_BindToTMU( 0, tr.currentRenderImage[backEnd.currentMainFBO] )
 	);
 
-	// The framebuffer should use GL_LINEAR for FXAA to work.
-	glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
-	glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
+	bool greaterThanGL33 = std::make_pair( glConfig.glMajor, glConfig.glMinor ) >= std::make_pair( 3, 3 );
+
+	// FXAA expect GL_LINEAR for the sampling to work.
+	if ( greaterThanGL33 )
+	{
+		// Bind a sampler.
+		GLuint sampler = 0;
+		glGenSamplers( 1, &sampler );
+		glSamplerParameteri( sampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR) ;
+		glSamplerParameteri( sampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
+		glBindSampler( 0, sampler );
+	}
+	else
+	{
+		// Change the filter (requires a texture bind).
+		glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
+		glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
+	}
 
 	// This shader is run last, so let it render to screen.
 	R_BindNullFBO();
 
 	Tess_InstantScreenSpaceQuad();
 
-	// Restore GL_NEAREST to not break other effects.
-	glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
-	glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
+	// Make sure we didn't break other effects expecting GL_NEAREST.
+	if ( greaterThanGL33 )
+	{
+		// Unbind the sampler.
+		glBindSampler( 0, 0 );
+	}
+	else
+	{
+		// Restore the filter (requires a texture bind).
+		glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
+		glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
+	}
 
 	GL_CheckErrors();
 }