From 2cb9476d139699efc3519a2c4403a69bc11a565c Mon Sep 17 00:00:00 2001
From: Emanuel Rabina <emanuelrabina@gmail.com>
Date: Fri, 28 Jun 2024 19:09:49 +1200
Subject: [PATCH] Clear program used in clear method

---
 .../graphics/opengl/OpenGLRenderer.groovy     | 21 +++++++++----------
 .../graphics/opengl/OpenGLShader.groovy       | 19 ++++++++++++++++-
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLRenderer.groovy b/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLRenderer.groovy
index 3a051567..6275a286 100644
--- a/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLRenderer.groovy
+++ b/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLRenderer.groovy
@@ -55,7 +55,6 @@ import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import static org.lwjgl.opengl.GL11C.*
 import static org.lwjgl.opengl.GL20C.GL_MAX_FRAGMENT_UNIFORM_COMPONENTS
-import static org.lwjgl.opengl.GL20C.glUseProgram
 import static org.lwjgl.opengl.GL30C.GL_FRAMEBUFFER
 import static org.lwjgl.opengl.GL30C.glBindFramebuffer
 import static org.lwjgl.opengl.GL31C.*
@@ -169,6 +168,16 @@ class OpenGLRenderer implements GraphicsRenderer {
 	@Override
 	void clear() {
 
+		// For an error w/ nVidia on Windows, where the program state seems to
+		// linger when creating a shader with a different layout, eg: we last used
+		// the Sharp Upscaling shader which has all of colour, position, and
+		// texcoord attributes, then try to create the Primitives shader which has
+		// only colour and position.  This then manifests as an error on the next
+		// frame when we call glClear() 🤔
+		// "Program/shader state performance warning: Vertex shader in program X
+		// is being recompiled based on GL state"
+		OpenGLShader.useProgram(0)
+
 		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
 	}
 
@@ -307,16 +316,6 @@ class OpenGLRenderer implements GraphicsRenderer {
 			}
 
 			trigger(new DrawEvent())
-
-			// For an error w/ nVidia on Windows, where the program state seems to
-			// linger when creating a shader with a different layout, eg: we last used
-			// the Sharp Upscaling shader which has all of colour, position, and
-			// texcoord attributes, then try to create the Primitives shader which has
-			// only colour and position.  This then manifests as an error on the next
-			// frame when we call glClear() 🤔
-			// "Program/shader state performance warning: Vertex shader in program X
-			// is being recompiled based on GL state"
-			glUseProgram(0)
 		}
 	}
 
diff --git a/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLShader.groovy b/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLShader.groovy
index a93d74f6..68d4fccd 100644
--- a/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLShader.groovy
+++ b/redhorizon-engine/source/nz/net/ultraq/redhorizon/engine/graphics/opengl/OpenGLShader.groovy
@@ -29,6 +29,7 @@ import static org.lwjgl.opengl.GL20C.*
 import static org.lwjgl.system.MemoryStack.stackPush
 
 import groovy.transform.Memoized
+import groovy.transform.PackageScope
 
 /**
  * OpenGL-specific shader implementation.
@@ -38,6 +39,7 @@ import groovy.transform.Memoized
 class OpenGLShader extends Shader {
 
 	private static final Logger logger = LoggerFactory.getLogger(OpenGLShader)
+	private static int lastProgramId = 0
 
 	final int programId
 
@@ -158,6 +160,21 @@ class OpenGLShader extends Shader {
 	@Override
 	void use() {
 
-		glUseProgram(programId)
+		useProgram(programId)
+	}
+
+	/**
+	 * Set to use the OpenGL shader program with the given ID.
+	 * <p>
+	 * This is only used by the {@link OpenGLRenderer} to reset the program used
+	 * so that program state doesn't bleed into the next one.
+	 */
+	@PackageScope
+	static void useProgram(int programId) {
+
+		if (programId != lastProgramId) {
+			glUseProgram(programId)
+			lastProgramId = programId
+		}
 	}
 }