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EditorZoomer - an easy way to do panning and zooming inside Unity Editor IMGUI
using UnityEngine;
using System.Collections;
using System;
//based on the code in this post: http://martinecker.com/martincodes/unity-editor-window-zooming/
//but I changed how the API works and made it much more flexible
//usage: create an EditorZoomer instance wherever you want to use it (it tracks the pan + zoom state)
//in your OnGUI, draw your scrollable content between zoomer.Begin() and zoomer.End();
//you also must offset your content by zoomer.GetContentOffset();
public class EditorZoomer
{
private const float kEditorWindowTabHeight = 21.0f;
public float zoom = 1f;
public Rect zoomArea = new Rect();
public Vector2 zoomOrigin = Vector2.zero;
Vector2 lastMouse = Vector2.zero;
Matrix4x4 prevMatrix;
public Rect Begin(params GUILayoutOption[] options)
{
HandleEvents();
//fill the available area
var possibleZoomArea = GUILayoutUtility.GetRect(0, 10000, 0, 10000, options);
if (Event.current.type == EventType.Repaint) //the size is correct during repaint, during layout it's 1,1
{
zoomArea = possibleZoomArea;
}
GUI.EndGroup(); // End the group Unity begins automatically for an EditorWindow to clip out the window tab. This allows us to draw outside of the size of the EditorWindow.
Rect clippedArea = zoomArea.ScaleSizeBy(1f/zoom, zoomArea.TopLeft());
clippedArea.y += kEditorWindowTabHeight;
GUI.BeginGroup(clippedArea);
prevMatrix = GUI.matrix;
Matrix4x4 translation = Matrix4x4.TRS(clippedArea.TopLeft(), Quaternion.identity, Vector3.one);
Matrix4x4 scale = Matrix4x4.Scale(new Vector3(zoom, zoom, 1.0f));
GUI.matrix = translation * scale * translation.inverse * GUI.matrix;
return clippedArea;
}
public void End()
{
GUI.matrix = prevMatrix; //restore the original matrix
GUI.EndGroup();
GUI.BeginGroup(new Rect(0.0f, kEditorWindowTabHeight, Screen.width, Screen.height));
}
public void HandleEvents()
{
if (Event.current.isMouse)
{
if (Event.current.type == EventType.MouseDrag && ((Event.current.button == 0 && Event.current.modifiers == EventModifiers.Alt) || Event.current.button == 2))
{
var mouseDelta = Event.current.mousePosition - lastMouse;
zoomOrigin += mouseDelta;
Event.current.Use();
}
lastMouse = Event.current.mousePosition;
}
if (Event.current.type == EventType.ScrollWheel)
{
float oldZoom = zoom;
float zoomChange = 1.10f;
zoom *= Mathf.Pow(zoomChange, -Event.current.delta.y / 3f);
zoom = Mathf.Clamp(zoom,0.1f, 10f);
bool shouldZoomTowardsMouse = true; //if this is false, it will always zoom towards the center of the content (0,0)
if (shouldZoomTowardsMouse)
{
//we want the same content that was under the mouse pre-zoom to be there post-zoom as well
//in other words, the content's position *relative to the mouse* should not change
Vector2 areaMousePos = Event.current.mousePosition - zoomArea.center;
Vector2 contentOldMousePos = (areaMousePos/oldZoom) - (zoomOrigin/oldZoom);
Vector2 contentMousePos = (areaMousePos/zoom) - (zoomOrigin/zoom);
Vector2 mouseDelta = contentMousePos - contentOldMousePos;
zoomOrigin += mouseDelta * zoom;
}
Event.current.Use();
}
}
public Vector2 GetContentOffset()
{
Vector2 offset = -zoomOrigin / zoom; //offset the midpoint
offset -= (zoomArea.size / 2f) / zoom; //offset the center
return offset;
}
}
// Helper Rect extension methods
public static class RectExtensions
{
public static Vector2 TopLeft(this Rect rect)
{
return new Vector2(rect.xMin, rect.yMin);
}
public static Rect ScaleSizeBy(this Rect rect, float scale)
{
return rect.ScaleSizeBy(scale, rect.center);
}
public static Rect ScaleSizeBy(this Rect rect, float scale, Vector2 pivotPoint)
{
Rect result = rect;
result.x -= pivotPoint.x;
result.y -= pivotPoint.y;
result.xMin *= scale;
result.xMax *= scale;
result.yMin *= scale;
result.yMax *= scale;
result.x += pivotPoint.x;
result.y += pivotPoint.y;
return result;
}
public static Rect ScaleSizeBy(this Rect rect, Vector2 scale)
{
return rect.ScaleSizeBy(scale, rect.center);
}
public static Rect ScaleSizeBy(this Rect rect, Vector2 scale, Vector2 pivotPoint)
{
Rect result = rect;
result.x -= pivotPoint.x;
result.y -= pivotPoint.y;
result.xMin *= scale.x;
result.xMax *= scale.x;
result.yMin *= scale.y;
result.yMax *= scale.y;
result.x += pivotPoint.x;
result.y += pivotPoint.y;
return result;
}
}
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