From 5364ead170ff66e0a13fc435117e1ea04f4eb273 Mon Sep 17 00:00:00 2001
From: sulai <6741822+sulai@users.noreply.github.com>
Date: Tue, 7 Jan 2025 19:49:58 +0100
Subject: [PATCH] Add GoogleMaps-like pinching (#12765)

Co-authored-by: mrimvo <6030346+mrimvo@users.noreply.github.com>
---
 .../ui/components/ZoomGestureListener.kt      | 27 +++++++++++--------
 .../components/widgets/ZoomableScrollPane.kt  |  9 ++++---
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/core/src/com/unciv/ui/components/ZoomGestureListener.kt b/core/src/com/unciv/ui/components/ZoomGestureListener.kt
index ae0faadb3274f..3dde8e68bec65 100644
--- a/core/src/com/unciv/ui/components/ZoomGestureListener.kt
+++ b/core/src/com/unciv/ui/components/ZoomGestureListener.kt
@@ -9,8 +9,8 @@ import com.badlogic.gdx.scenes.scene2d.InputEvent
 open class ZoomGestureListener(
     halfTapSquareSize: Float, tapCountInterval: Float, longPressDuration: Float, maxFlingDelay: Float
 ) : EventListener {
-    val detector: GestureDetector
-    var event: InputEvent? = null
+    
+    private val detector: GestureDetector
 
     constructor() : this(20f, 0.4f, 1.1f, Int.MAX_VALUE.toFloat())
 
@@ -22,22 +22,29 @@ open class ZoomGestureListener(
             maxFlingDelay,
             object : GestureDetector.GestureAdapter() {
 
-                override fun zoom(initialDistance: Float, distance: Float): Boolean {
-                    this@ZoomGestureListener.zoom(initialDistance, distance)
-                    return true
-                }
-
+                private var pinchCenter: Vector2? = null
+                private var initialDistance = 0f
+                
                 override fun pinch(
                     stageInitialPointer1: Vector2,
                     stageInitialPointer2: Vector2,
                     stagePointer1: Vector2,
                     stagePointer2: Vector2
                 ): Boolean {
-                    this@ZoomGestureListener.pinch()
+                    if (pinchCenter == null) {
+                        pinchCenter = stageInitialPointer1.cpy().add(stageInitialPointer2).scl(.5f)
+                        initialDistance = stageInitialPointer1.dst(stageInitialPointer2)
+                    }
+                    val currentCenter = stagePointer1.cpy().add(stagePointer2).scl(.5f)
+                    val delta = currentCenter.cpy().sub(pinchCenter)
+                    pinchCenter = currentCenter.cpy()
+                    this@ZoomGestureListener.pinch(delta)
+                    this@ZoomGestureListener.zoom(initialDistance, stagePointer1.dst(stagePointer2))
                     return true
                 }
 
                 override fun pinchStop() {
+                    pinchCenter = null
                     this@ZoomGestureListener.pinchStop()
                 }
             })
@@ -61,12 +68,10 @@ open class ZoomGestureListener(
                     detector.reset()
                     return false
                 }
-                this.event = event
                 detector.touchUp(event.stageX, event.stageY, event.pointer, event.button)
                 return true
             }
             InputEvent.Type.touchDragged -> {
-                this.event = event
                 detector.touchDragged(event.stageX, event.stageY, event.pointer)
                 return true
             }
@@ -79,6 +84,6 @@ open class ZoomGestureListener(
 
     open fun scrolled(amountX: Float, amountY: Float): Boolean { return false }
     open fun zoom(initialDistance: Float, distance: Float) {}
-    open fun pinch() {}
+    open fun pinch(delta: Vector2) {}
     open fun pinchStop() {}
 }
diff --git a/core/src/com/unciv/ui/components/widgets/ZoomableScrollPane.kt b/core/src/com/unciv/ui/components/widgets/ZoomableScrollPane.kt
index 3853f884963cd..073fe79e040da 100644
--- a/core/src/com/unciv/ui/components/widgets/ZoomableScrollPane.kt
+++ b/core/src/com/unciv/ui/components/widgets/ZoomableScrollPane.kt
@@ -246,11 +246,16 @@ open class ZoomableScrollPane(
             }
         }
 
-        override fun pinch() {
+        override fun pinch(delta: Vector2) {
             if (!isZooming) {
                 isZooming = true
                 onZoomStartListener?.invoke()
             }
+            scrollTo(
+                scrollX - delta.x,
+                scrollY + delta.y,
+                true
+            )
         }
 
         override fun pinchStop() {
@@ -317,8 +322,6 @@ open class ZoomableScrollPane(
 
             //clamp() call is missing here but it doesn't seem to make any big difference in this case
 
-            if ((isScrollX && deltaX != 0f || isScrollY && deltaY != 0f))
-                cancelTouchFocus()
         }
 
         override fun panStop(event: InputEvent?, x: Float, y: Float, pointer: Int, button: Int) {