What is the mathematical formula for GUI dragging ?

Question

Hi , when working with unity's GUI , there is a formula w$$anonymous$$ch is used when creating a drag behavior for GUI.Box, GUI.Button, GUI.DrawTexture etc....

I want to be able to drag any GUI no matter where on the GUI i click and drag . I just wrote t$$anonymous$$s here but t$$anonymous$$s code should do that . The problem is , my drag formula is wrong .

for example

 public class DragSomet$$anonymous$$ng: EditorWindow
 {
     private Rect DrawTextureRect = new Rect(0, 0, 50, 50); // reck of gui we will drag
 private bool Dragging ; // bool to check if we are dragging ...if mouse is down

 private float Xpos, Ypos, Xwidth, Yheight; // so that we can work with each value 

 private Rect GUIposition(Vector2 mousePosition,Rect guiRect)
 {
 
     // our bad math formula w$$anonymous$$ch will drag our gui but actually just throws the gui into a corner ... literally
     Xpos = mousePosition.x - DrawTextureRect.x; // if we had 540 as mousePosition.x  and 500 as DrawTextureRect.x , Xpos would be equal to 40 ... w$$anonymous$$ch is very bad 

 Ypos = mousePosition.y - DrawTextureRect.y;  // same here 

 Xwidth = DrawTextureRect .width;// t$$anonymous$$s is fine

 Yheight = DrawTextureRect .height;// t$$anonymous$$s is fine too

 return(new Rect(Xpos, Ypos, Xwidth, Yheight));
 }
 
 
 void OnGUI()
 {
 
  if (Event.current.type == EventType.MouseUp)
             {
                 Dragging = false;
             }
  if (Event.current.type == EventType.MouseDown && DrawTextureRect.Contains (Event.current.mousePosition))
             {
                 Dragging = true;
             }
 
 if(Dragging )
 {
 GUIposition(Event.current.mousePosition,DrawTextureRect); // give it the mouse position and the rect of the bui we want to drag
 }
 }

 GUI.DrawTexture(DrawTextureRect,sometexture);
 
 }

Answer 1

Best Answer

Answer by primemover · Mar 04, 2015 at 04:36 AM

When you capture mouse down in your Rect, find out how far you away from the Rects origin in x and y, then capture the mouse and subtract the x and y you found. Like what Glurth said.

Try t$$anonymous$$s:

Make a Vector2 called cursorOffset.

Place t$$anonymous$$s where you have Dragging = true, before it.

 cursorOffset.x = Event.current.mousePosition.x - DrawTextureRect.x;
 cursorOffset.y = Event.current.mousePosition.y - DrawTextureRect.y;

Then your math would be:

 Xpos = Event.current.mousePosition.x - cursorOffset.x;
 Ypos = Event.current.mousePosition.y - cursorOffset.y;

I t$$anonymous$$nk that might work.

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DaiMangouDev · Mar 04, 2015 at 02:47 PM 0

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also works . I guess the formula comes in different forms but it is essentially always the same .

Answer 2

I was given an example of offset usage w$$anonymous$$ch i had been unaware of

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 
 public class TestWindow : EditorWindow {
 
     [MenuItem ("Window/Test Window")]
     static void Init () {
         // Get existing open window or if none, make a new one:
         TestWindow window = (TestWindow)EditorWindow.GetWindow (typeof (TestWindow));
         window.Show();
     }
     
     Texture2D pixel;
     Rect windowRect;
     bool isDragging;
     Vector2 offset;
     
     public TestWindow()
     {
         pixel = new Texture2D(1, 3, TextureFormat.ARGB32, true);
         pixel.SetPixel(0, 0, new Color(1, 1, 1, 1));
         pixel.Apply();
         
         windowRect = new Rect(10,10,100,100);
         isDragging = false;
         offset = Vector2.zero;
     }
     
     void OnGUI()
     {
         //update
         Event evt = Event.current;
         
         switch(evt.type)
         {
             case EventType.MouseDown:
                 if(windowRect.Contains(evt.mousePosition))
                 {
                     isDragging=true; 
                   
                     //get offset from mouse
                 offset = evt.mousePosition - windowRect.position;
                 }
                 break;
             case EventType.MouseUp:
                 isDragging = false;
                 break;
             case EventType.MouseDrag:
                 if(isDragging)
                 {
                     windowRect.position = evt.mousePosition - offset;
                 }
                 break;
         }
         
         //render
         GUI.DrawTexture(windowRect,pixel);
         
         Repaint ();
     }

What is the mathematical formula for GUI dragging ?

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