A patch for MCP (1.8 - 1.8.9) which enables GLSLSandbox MainMenu shaders

shader_background.patch

Index: src/minecraft/net/minecraft/client/gui/GuiMainMenu.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/minecraft/net/minecraft/client/gui/GuiMainMenu.java	(date 1591536256953)
+++ src/minecraft/net/minecraft/client/gui/GuiMainMenu.java	(date 1591536256953)
@@ -25,10 +25,12 @@
 import net.minecraft.world.demo.DemoWorldServer;
 import net.minecraft.world.storage.ISaveFormat;
 import net.minecraft.world.storage.WorldInfo;
+import net.superblaubeere27.glslsandboxrenderer.GLSLSandboxShader;
 import org.apache.commons.io.Charsets;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.lwjgl.opengl.GL11;
+import org.lwjgl.opengl.GL20;
 import org.lwjgl.opengl.GLContext;
 import org.lwjgl.util.glu.Project;
 
@@ -84,6 +86,9 @@
     /** Minecraft Realms button. */
     private GuiButton realmsButton;
 
+    private GLSLSandboxShader backgroundShader;
+    private long initTime = System.currentTimeMillis(); // Initialize as a failsafe
+
     public GuiMainMenu()
     {
         this.openGLWarning2 = field_96138_a;
@@ -147,6 +152,12 @@
             this.openGLWarning2 = I18n.format("title.oldgl2", new Object[0]);
             this.openGLWarningLink = "https://help.mojang.com/customer/portal/articles/325948?ref=game";
         }
+
+        try {
+            this.backgroundShader = new GLSLSandboxShader("/noise.fsh");
+        } catch (IOException e) {
+            throw new IllegalStateException("Failed to load backgound shader", e);
+        }
     }
 
     /**
@@ -225,6 +236,8 @@
         }
 
         this.mc.func_181537_a(false);
+
+        initTime = System.currentTimeMillis();
     }
 
     /**
@@ -503,16 +516,28 @@
      */
     public void drawScreen(int mouseX, int mouseY, float partialTicks)
     {
-        GlStateManager.disableAlpha();
-        this.renderSkybox(mouseX, mouseY, partialTicks);
         GlStateManager.enableAlpha();
-        Tessellator tessellator = Tessellator.getInstance();
-        WorldRenderer worldrenderer = tessellator.getWorldRenderer();
+        GlStateManager.disableCull();
         int i = 274;
         int j = this.width / 2 - i / 2;
         int k = 30;
-        this.drawGradientRect(0, 0, this.width, this.height, -2130706433, 16777215);
-        this.drawGradientRect(0, 0, this.width, this.height, 0, Integer.MIN_VALUE);
+
+        this.backgroundShader.useShader(this.width, this.height, mouseX, mouseY, (System.currentTimeMillis() - initTime) / 1000f);
+
+        GL11.glBegin(GL11.GL_QUADS);
+
+        GL11.glVertex2f(-1f, -1f);
+        GL11.glVertex2f(-1f, 1f);
+        GL11.glVertex2f(1f, 1f);
+        GL11.glVertex2f(1f, -1f);
+
+        GL11.glEnd();
+
+        // Unbind shader
+        GL20.glUseProgram(0);
+
+        // Stuff enabled done by the skybox rendering
+
         this.mc.getTextureManager().bindTexture(minecraftTitleTextures);
         GlStateManager.color(1.0F, 1.0F, 1.0F, 1.0F);