Drawing a textured rectangle in a Minecraft GUI

GuiTexturedRect.java

// HOW TO DRAW A TEXTURED RECTANGLE IN A MINECRAFT GUI WITH THE TEXTURE SCALED TO FIT
//
//
// 1. You need an instance of RenderEngine. Using ModLoader you can obtain it with:
//
RenderEngine renderEngine = ModLoader.getMinecraftInstance().renderEngine;
 
// 2a. When your mod first starts, you need to load your texture into OpenGL. If your image
//     file is on the classpath (i.e. inside minecraft.jar or inside your own mod's jar) then
//     you can load it easily. Your image file should contain an alpha layer with only 0 or 255
//     values. Load the file using (the leading slash is important here):
int myTextureName = renderEngine.getTexture("/foobar.png");

// 2b. Alternatively, if you are loading the texture from the network or computing it on the fly,
//     you'll have to provide your own code to setup a BufferedImage with your texture image
//     (use TYPE_INT_ARGB for the imageType). Then you can load it with:
int myTextureName = renderEngine.allocateAndSetupTexture(myBufferedImage);
 
// 3.  You'll need to write your own version of the Gui.drawTexturedModalRect() method
//     This method can go into your own Gui class:
 public void myDrawTexturedModalRect(int x, int y, int width, int height)
{
    Tessellator tessellator = Tessellator.instance;
    tessellator.startDrawingQuads();    
    tessellator.addVertexWithUV(x        , y + height, 0, 0.0, 1.0);
    tessellator.addVertexWithUV(x + width, y + height, 0, 1.0, 1.0);
    tessellator.addVertexWithUV(x + width, y         , 0, 1.0, 0.0);
    tessellator.addVertexWithUV(x        , y         , 0, 0.0, 0.0);
    tessellator.draw();
}

// 4.  Somewhere in your own Gui class's drawScreen() method, you draw the rectangle with:
renderEngine.bindTexture(myTextureName);
myDrawTextureModalRect(x, y, w, h);

// NOTE: Your texture image does not have to be square but its width and height should both
// be a power of 2 like 32x64, 16x128, 8x4, etc.