Enable stacking shaders

api/src/main/java/com/bartlomiejpluta/base/internal/render/ShaderManager.java

@@ -6,11 +6,9 @@ import org.joml.*;
 public interface ShaderManager extends Cleanable {
    ShaderManager createShader(String programName, String vertexShaderFilename, String fragmentShaderFilename);
 
-   ShaderManager selectShader(String programName);
+   ShaderManager activateShader(String programName);
 
-   ShaderManager useSelectedShader();
-
-   ShaderManager detachCurrentShader();
+   ShaderManager deactivateShader();
 
    ShaderManager createUniform(String uniformName);
 

engine/src/main/java/com/bartlomiejpluta/base/engine/core/gl/render/DefaultRenderer.java

@@ -4,6 +4,7 @@ import com.bartlomiejpluta.base.api.camera.Camera;
 import com.bartlomiejpluta.base.api.screen.Screen;
 import com.bartlomiejpluta.base.engine.core.gl.shader.constant.CounterName;
 import com.bartlomiejpluta.base.engine.core.gl.shader.constant.RenderConstants;
+import com.bartlomiejpluta.base.engine.core.gl.shader.constant.Shader;
 import com.bartlomiejpluta.base.engine.core.gl.shader.constant.UniformName;
 import com.bartlomiejpluta.base.internal.render.Renderable;
 import com.bartlomiejpluta.base.internal.render.ShaderManager;
@@ -12,6 +13,8 @@ import lombok.extern.slf4j.Slf4j;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
 
+import java.util.Arrays;
+
 import static org.lwjgl.opengl.GL15.*;
 
 @Slf4j
@@ -23,9 +26,15 @@ public class DefaultRenderer implements Renderer {
    @Override
    public void init() {
       log.info("Initializing renderer");
+
+      log.info("Registering shaders");
+      for (var shader : Shader.values()) {
+         shaderManager.createShader(shader.name, shader.vertex, shader.fragment);
+      }
+
+      log.info("Registering uniforms");
       shaderManager
-         .createShader("default", "/shaders/default.vs", "/shaders/default.fs")
-         .selectShader("default")
+         .activateShader(Shader.DEFAULT.name)
          .createUniform(UniformName.UNI_VIEW_MODEL_MATRIX)
          .createUniform(UniformName.UNI_MODEL_MATRIX)
          .createUniform(UniformName.UNI_PROJECTION_MATRIX)
@@ -52,7 +61,7 @@ public class DefaultRenderer implements Renderer {
       clear();
       updateViewport(screen);
 
-      shaderManager.selectShader("default").useSelectedShader();
+      shaderManager.activateShader(Shader.DEFAULT.name);
       shaderManager.resetCounters();
 
       // Important note:
@@ -62,7 +71,7 @@ public class DefaultRenderer implements Renderer {
       camera.render(screen, shaderManager);
       renderable.render(screen, camera, shaderManager);
 
-      shaderManager.detachCurrentShader();
+      shaderManager.deactivateShader();
 
       screen.restoreState();
    }

engine/src/main/java/com/bartlomiejpluta/base/engine/core/gl/shader/constant/Shader.java

@@ -0,0 +1,12 @@
+package com.bartlomiejpluta.base.engine.core.gl.shader.constant;
+
+import lombok.RequiredArgsConstructor;
+
+@RequiredArgsConstructor
+public enum Shader {
+   DEFAULT("default", "/shaders/default.vs", "/shaders/default.fs");
+
+   public final String name;
+   public final String vertex;
+   public final String fragment;
+}

engine/src/main/java/com/bartlomiejpluta/base/engine/core/gl/shader/manager/DefaultShaderManager.java

@@ -12,7 +12,9 @@ import org.joml.*;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
 
+import java.util.Deque;
 import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -25,6 +27,7 @@ public class DefaultShaderManager implements ShaderManager {
    private final ResourcesManager resourcesManager;
    private final Map<String, ShaderProgram> shaders = new HashMap<>();
    private final Map<String, AtomicInteger> counters = new HashMap<>();
+   private final Deque<ShaderProgram> stack = new LinkedList<>();
    private ShaderProgram current;
 
    @Override
@@ -40,20 +43,19 @@ public class DefaultShaderManager implements ShaderManager {
    }
 
    @Override
-   public ShaderManager selectShader(String programName) {
+   public ShaderManager activateShader(String programName) {
       current = shaders.get(programName);
-      return this;
-   }
-
-   @Override
-   public ShaderManager useSelectedShader() {
+      stack.push(current);
       current.use();
       return this;
    }
 
    @Override
-   public ShaderManager detachCurrentShader() {
+   public ShaderManager deactivateShader() {
       current.detach();
+      stack.pop();
+      current = stack.peek();
+      current.use();
       return this;
    }