From 11151ca6f0be82d56207e4f482722a0e304d02fe Mon Sep 17 00:00:00 2001
From: Carlos Aragones <c.aragones@gamehouse.com>
Date: Tue, 16 Nov 2021 09:55:27 +0100
Subject: [PATCH] Add option to invert the Mouse Y coordinate on MacOS

---
 CMakeLists.txt       |  5 +++++
 README.md            | 14 ++++++++++++++
 src/macosx/OSXView.m |  6 +++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 66b1a32..01cf2f4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -104,6 +104,7 @@ option(MINIFB_BUILD_EXAMPLES "Build minifb example programs" TRUE)
 
 if(APPLE AND NOT IOS)
     option(USE_METAL_API "Build the project using metal API code" ON)
+    option(USE_INVERTED_Y_ON_MACOS "Use default mouse position: (0, 0) at (left, down)" OFF)
 elseif(UNIX)
     option(USE_WAYLAND_API "Build the project using wayland API code" OFF)
     if(NOT USE_WAYLAND_API)
@@ -180,6 +181,10 @@ elseif(APPLE)
         add_definitions(-DUSE_METAL_API)
     endif()
 
+    if(USE_INVERTED_Y_ON_MACOS)
+        add_definitions(-DUSE_INVERTED_Y_ON_MACOS)
+    endif()
+
     list(APPEND SrcLib ${SrcMacOSX})
 
 elseif(UNIX)
diff --git a/README.md b/README.md
index b30e74c..1ef65ff 100644
--- a/README.md
+++ b/README.md
@@ -186,6 +186,20 @@ cd build
 cmake .. -DUSE_METAL_API=OFF
 ```
 
+#### Coordinate system
+
+On MacOS, the default mouse coordinate system is (0, 0) -> (left, bottom). But as we want to create a multiplatform library we inverted the coordinates in such a way that now (0, 0) -> (left, top), like in the other platforms.
+
+In any case, if you want to get the default coordinate system you can use the CMake flag: USE_INVERTED_Y_ON_MACOS=ON
+
+```
+mkdir build
+cd build
+cmake .. -DUSE_INVERTED_Y_ON_MACOS=ON
+```
+
+_Note: In the future, we may use a global option so that all platforms behave in the same way. Probably: -DUSE_INVERTED_Y_
+
 if you use **tundra**:
 
 ```
diff --git a/src/macosx/OSXView.m b/src/macosx/OSXView.m
index 0bf0378..b00fca3 100644
--- a/src/macosx/OSXView.m
+++ b/src/macosx/OSXView.m
@@ -186,8 +186,12 @@
         NSPoint point = [event locationInWindow];
         //NSPoint localPoint = [self convertPoint:point fromView:nil];
         window_data->mouse_pos_x = point.x;
+#if defined(USE_INVERTED_Y_ON_MACOS)
         window_data->mouse_pos_y = point.y;
-        kCall(mouse_move_func, point.x, point.y);
+#else
+        window_data->mouse_pos_y = window_data->window_height - point.y;
+#endif
+        kCall(mouse_move_func, window_data->mouse_pos_x, window_data->mouse_pos_y);
     }
 }