GUI.DrawTexture on GUI.Button press

Question

I've got a GUI menu with a GUI button on it, when the button is pressed I want a GUI texture to come up which will display information. Ive got the following script but when I click the button, it doesn't bring the texture up (I've assigned it in the Inspector):

 using UnityEngine;
 using System.Collections;
 
 public class GUIDisplay : MonoBehaviour 
 {
     public Texture2D background;
     public Texture2D helpPage;
 
     void OnGUI()
     {
         GUI.DrawTexture(new Rect(0,0,Screen.width,Screen.height),background);
         GUI.backgroundColor = Color.clear;
         if(GUI.Button(new Rect(Screen.width * (4.5f/6.55f),Screen.height * (5.25f/6.3f),Screen.width * (0.8f/6.55f), Screen.height * (0.85f/6.3f)),""))
             GUI.DrawTexture(new Rect(0,0,Screen.width,Screen.height),helpPage);
                 }
             }

Any ideas what I'm doing wrong?

Alternatively, I could activate and deactivate the texture, I tried:

 helpPage.SetActive(true);

and

 helpPage.enabled = true;

But neither of these worked. (I'm using C# by the way)

Answer 1

Best Answer

Answer by troien · Oct 15, 2014 at 01:16 PM

The problem is that the OnGUI method is called a lot. (depending on the event) OnGUI gets called once per frame for the Repaint event for instance. And whenever you mousedown, mouseup, mousemove etc. OnGUI will be called additional times for each event.

Your problem is that the content of the if(GUI.Button()) call only gets called on the mouseUP event. Not the repaint event. so any GUI calls inside are basically ignored.

So the thing you could do is something like the following

 using UnityEngine;
 using System.Collections;
  
 public class GUIDisplay : MonoBehaviour 
 {
     public Texture2D background;
     public Texture2D helpPage;
 
     private bool clicked = false;
  
     void OnGUI()
     {
         GUI.DrawTexture(new Rect(0,0,Screen.width,Screen.height),background);
         GUI.backgroundColor = Color.clear;
         if(GUI.Button(new Rect(Screen.width * (4.5f/6.55f),Screen.height * (5.25f/6.3f),Screen.width * (0.8f/6.55f), Screen.height * (0.85f/6.3f)),""))
             clicked = true;
 
         if (clicked)
             GUI.DrawTexture(new Rect(0,0,Screen.width,Screen.height),helpPage);
     }
 }

For more information about how OnGUI works you should check the docs.

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hollym16 · Oct 15, 2014 at 01:41 PM 0

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Thanks, it works brilliantly. How would I go about 'undrawing' the texture? There's a button on the texture I activated that, when clicked, I want to deactivate. If that makes any sense?

troien · Oct 15, 2014 at 02:03 PM 0

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well, setting "clicked" to false again will stop everything inside "if (clicked)" from geting called. Therefore I think that the following example should point you in the right direction.

 if (clicked)
         {
             GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), helpPage);
             if (GUI.Button(new Rect(0, 0, 100,50),""))
                 clicked = false;
         }

ps. you should really take note to the "gets called once per frame" part of my answer. with this I also meant that every frame the entire GUI will be clearded and re-drawn. and therefore there doesn't exist something like 'undrawing' something in Unity OnGUI.

GUI.DrawTexture on GUI.Button press

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