Code

package de.thexxturboxx.craftoflegends.gui;

import java.io.IOException;
import java.util.List;

import org.lwjgl.input.Keyboard;
import org.lwjgl.input.Mouse;
import org.lwjgl.opengl.GL11;

import de.thexxturboxx.craftoflegends.COLMod;
import de.thexxturboxx.craftoflegends.COLRegistry;
import de.thexxturboxx.craftoflegends.api.DataManager;
import de.thexxturboxx.craftoflegends.api.PLAYER_PROPERTY;
import de.thexxturboxx.craftoflegends.items.InvItem;
import de.thexxturboxx.craftoflegends.util.Helpers;
import net.minecraft.client.gui.GuiScreen;
import net.minecraft.util.ResourceLocation;
import scala.actors.threadpool.Arrays;

public class GuiShop extends GuiScreen {

	int guiWidth = 256;
	int guiHeight = 137;

	int realGuiWidth = 512;
	int realGuiHeight = 274;

	int goldWidth = 32;
	int goldHeight = 16;

	int scaleFactor = 2;

	int scroll = 0;
	int itemsPerLine = 7;
	int linesPerGui = 7;

	//GuiButton button;

	@Override
	public void drawScreen(int x, int y, float ticks) {
		int guiX = ((width - realGuiWidth) / 2 / scaleFactor);
		int guiY = ((height - realGuiHeight) / 2 / scaleFactor);
		GL11.glColor4f(1, 1, 1, 1);
		drawDefaultBackground();
		mc.renderEngine.bindTexture(new ResourceLocation(COLMod.ID, "textures/gui/datageneral.png"));
		GL11.glScaled(scaleFactor, scaleFactor, scaleFactor);
		drawTexturedModalRect(guiX, guiY, 0, 0, guiWidth, guiHeight);
		String s = Integer.toString(DataManager.getProperty(mc.thePlayer.getUniqueID().toString(), PLAYER_PROPERTY.GOLD));
		int xx = (16 + fontRendererObj.getStringWidth(s)) / 2;
		drawTexturedModalRect(guiX + (guiWidth / 2) - xx, guiY + 2, 0, guiHeight, goldWidth, goldHeight);
		fontRendererObj.drawString(s, guiX + (guiWidth / 2) + xx, guiY + 4, 0xffffff, false);
		GL11.glScaled((1 / (double) scaleFactor), (1 / (double) scaleFactor), (1 / (double) scaleFactor));
		int c = 0;
		for(InvItem is : COLRegistry.itemList) {
			InvItem i = COLRegistry.itemList.get(scroll * itemsPerLine + c);
			if(c < itemsPerLine * 10) {
				ResourceLocation r = new ResourceLocation(COLMod.ID, "textures/items/" + i.getName() + ".png");
				drawNextItem(i, r, c++, itemsPerLine);
			}
		}
		super.drawScreen(x, y, ticks);
	}

	protected void drawNextItem(InvItem i, ResourceLocation r, int number, int itemsPerLine) {
		int guiX = (width - realGuiWidth) / scaleFactor;
		int guiY = (height - realGuiHeight) / scaleFactor;
		GL11.glColor4f(1, 1, 1, 1);
		mc.renderEngine.bindTexture(r);
		int lineX = (number % itemsPerLine) + 1;
		int lineY = (number - lineX + 1) / itemsPerLine;
		int itemX = guiX + ((lineX - 1) * 32) + 3;
		int itemY = guiY + (lineY * 32) + 33;
		GL11.glScaled(0.0625, 0.0625, 0.0625);
		drawTexturedModalRect(16 * (itemX + 5), 16 * itemY, 0, 0, 256, 256);
		String cost = Integer.toString(i.getCost());
		int stringX = (itemX + 13) - ((fontRendererObj.getStringWidth(cost) + 1) / 2);
		int stringY = itemY + 17;
		GL11.glScaled(16, 16, 16);
		GL11.glColor4d(0.5, 0.5, 0.5, 1);
		fontRendererObj.drawString(cost, stringX, stringY, 0x557661);
	}

	@Override
	protected void keyTyped(char typedChar, int keyCode) throws IOException {
		if(keyCode == Keyboard.KEY_DOWN) {
			if(scroll + 1 <= Math.ceil(((double) COLRegistry.itemList.size() / (double) itemsPerLine)) - linesPerGui) {
				scroll++;
			}
		}
		if(keyCode == Keyboard.KEY_UP) {
			if(scroll - 1 >= 0) {
				scroll--;
			}
		}
		super.keyTyped(typedChar, keyCode);
	}

	@Override
	public void handleMouseInput() throws IOException {
		for(int number = 0; number < COLRegistry.itemList.size(); number++) {
			int guiX = (width - realGuiWidth) / scaleFactor;
			int guiY = (height - realGuiHeight) / scaleFactor;
			int lineX = (number % itemsPerLine) + 1;
			int lineY = (number - lineX + 1) / itemsPerLine;
			int itemX = guiX + ((lineX - 1) * 32) + 3;
			int itemY = guiY + (lineY * 32) + 33;
			int i = Mouse.getEventX() * this.width / this.mc.displayWidth;
	        int j = this.height - Mouse.getEventY() * this.height / this.mc.displayHeight - 4;
			if(i >= itemX && j >= itemY && i <= itemX + 16 && j <= itemY + 16) {
				String[] sa = new String[] {Helpers.translate("item." + COLRegistry.itemList.get(number).getName() + ".name")};
				List<String> s = Arrays.asList(sa);
				drawHoveringText(s, i, j);
			}
		}
		super.handleMouseInput();
	}
}