From 097891e311fae1d8354eb092a0fd0171e630d78c Mon Sep 17 00:00:00 2001
From: thewoz <leonardo.parisi@gmail.com>
Date: Wed, 12 Apr 2023 09:32:46 +0200
Subject: [PATCH] Merge pull request #23394 from thewoz:Cocoa-Scroll-Wheel

Add scrollWheel to Cocoa #23394

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake
---
 modules/highgui/include/opencv2/highgui.hpp |  2 +-
 modules/highgui/src/window_cocoa.mm         | 23 +++++++++++++++++++--
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/modules/highgui/include/opencv2/highgui.hpp b/modules/highgui/include/opencv2/highgui.hpp
index 32f6dfb25d7e..71c0cf6e85bb 100644
--- a/modules/highgui/include/opencv2/highgui.hpp
+++ b/modules/highgui/include/opencv2/highgui.hpp
@@ -504,7 +504,7 @@ left scrolling, respectively.
 
 @note
 
-Mouse-wheel events are currently supported only on Windows.
+Mouse-wheel events are currently supported only on Windows and Cocoa
 
 @param flags The mouse callback flags parameter.
  */
diff --git a/modules/highgui/src/window_cocoa.mm b/modules/highgui/src/window_cocoa.mm
index 3f44deb1f179..762d57943821 100644
--- a/modules/highgui/src/window_cocoa.mm
+++ b/modules/highgui/src/window_cocoa.mm
@@ -899,8 +899,22 @@ - (void)cvSendMouseEvent:(NSEvent *)event type:(int)type flags:(int)flags {
     mp.y *= (imageSize.height / std::max(viewSize.height, 1.));
     mp.x *= (imageSize.width / std::max(viewSize.width, 1.));
 
-    if( mp.x >= 0 && mp.y >= 0 && mp.x < imageSize.width && mp.y < imageSize.height )
-        mouseCallback(type, mp.x, mp.y, flags, mouseParam);
+    if( [event type] == NSEventTypeScrollWheel ) {
+      if( event.hasPreciseScrollingDeltas ) {
+        mp.x = int(event.scrollingDeltaX);
+        mp.y = int(event.scrollingDeltaY);
+      } else {
+        mp.x = int(event.scrollingDeltaX / 0.100006);
+        mp.y = int(event.scrollingDeltaY / 0.100006);
+      }
+      if( mp.x && !mp.y && CV_EVENT_MOUSEWHEEL == type ) {
+        type = CV_EVENT_MOUSEHWHEEL;
+      }
+      mouseCallback(type, mp.x, mp.y, flags, mouseParam);
+    } else if( mp.x >= 0 && mp.y >= 0 && mp.x < imageSize.width && mp.y < imageSize.height ) {
+      mouseCallback(type, mp.x, mp.y, flags, mouseParam);
+    }
+
 }
 
 - (void)cvMouseEvent:(NSEvent *)event {
@@ -923,6 +937,11 @@ - (void)cvMouseEvent:(NSEvent *)event {
     if([event type] == NSLeftMouseDragged) {[self cvSendMouseEvent:event type:CV_EVENT_MOUSEMOVE   flags:flags | CV_EVENT_FLAG_LBUTTON];}
     if([event type] == NSRightMouseDragged)	{[self cvSendMouseEvent:event type:CV_EVENT_MOUSEMOVE   flags:flags | CV_EVENT_FLAG_RBUTTON];}
     if([event type] == NSOtherMouseDragged)	{[self cvSendMouseEvent:event type:CV_EVENT_MOUSEMOVE   flags:flags | CV_EVENT_FLAG_MBUTTON];}
+    if([event type] == NSEventTypeScrollWheel) {[self cvSendMouseEvent:event type:CV_EVENT_MOUSEWHEEL   flags:flags ];}
+}
+
+-(void)scrollWheel:(NSEvent *)theEvent {
+    [self cvMouseEvent:theEvent];
 }
 - (void)keyDown:(NSEvent *)theEvent {
     //cout << "keyDown" << endl;