Resizing BS!

src/teavm/java/com/mojang/minecraft/Minecraft.java

@@ -244,6 +244,20 @@ public final class Minecraft implements Runnable {
                 	  this.ungrabMouse();
                   }
                   
+                  if(this.width != GL11.parent.getClientWidth() || this.height != GL11.parent.getClientHeight()) {
+                	  this.width = GL11.parent.getClientWidth();
+                	  this.height = GL11.parent.getClientHeight();
+                	  GL11.canvas.setWidth(width);
+                	  GL11.canvas.setHeight(height);
+                	  GL11.updateDisplay();
+                	  if (currentScreen != null) {
+              			ScaledResolution scaledresolution = new ScaledResolution(width, height);
+              			int k = scaledresolution.getScaledWidth();
+              			int l = scaledresolution.getScaledHeight();
+              			currentScreen.setWorldAndResolution(this, k, l);
+              		}
+                  }
+
                   checkGLError("Pre render");
                   GL11.glEnable(3553);
                   if(!this.online) {

src/teavm/java/com/mojang/minecraft/ScaledResolution.java

@@ -0,0 +1,26 @@
+package com.mojang.minecraft;
+
+public class ScaledResolution {
+
+	public ScaledResolution(int i, int j) {
+		scaledWidth = i;
+		scaledHeight = j;
+		for (scaleFactor = 1; scaledWidth / (scaleFactor + 1) >= 320
+				&& scaledHeight / (scaleFactor + 1) >= 240; scaleFactor++) {
+		}
+		scaledWidth = scaledWidth / scaleFactor;
+		scaledHeight = scaledHeight / scaleFactor;
+	}
+
+	public int getScaledWidth() {
+		return scaledWidth;
+	}
+
+	public int getScaledHeight() {
+		return scaledHeight;
+	}
+
+	private int scaledWidth;
+	private int scaledHeight;
+	public int scaleFactor;
+}

src/teavm/java/com/mojang/minecraft/gui/GuiScreen.java

@@ -74,6 +74,15 @@ public class GuiScreen extends Screen {
 
    protected void onButtonClick(Button var1) {}
    
+   public void setWorldAndResolution(Minecraft minecraft, int i, int j) {
+		this.minecraft = minecraft;
+		fontRenderer = minecraft.fontRenderer;
+		width = i;
+		height = j;
+		buttons.clear();
+		onOpen();
+	}
+
    public final void open(Minecraft var1, int var2, int var3) {
       this.minecraft = var1;
       this.fontRenderer = var1.fontRenderer;