FLUID: allow mousewheel events on coordinate input

MACOS: make sure that even small mouse wheel deltas count at least as 1 unit

3 files changed, 25 insertions, 2 deletions

diff --git a/fluid/custom_widgets.cxx b/fluid/custom_widgets.cxx
index 170ef44a2..f409e9761 100644
--- a/fluid/custom_widgets.cxx
+++ b/fluid/custom_widgets.cxx
@@ -292,3 +292,19 @@ void Fluid_Coord_Input::value(int v) {
   fl_snprintf(buf, sizeof(buf), "%d", v);
   text(buf);
 }
+
+/**
+ Allow vertical mouse dragging and mouse wheel to interactively change the value.
+ */
+int Fluid_Coord_Input::handle(int event) {
+  switch (event) {
+    case FL_MOUSEWHEEL:
+      if (Fl::event_dy()) {
+        value( value() - Fl::event_dy() );
+        set_changed();
+        do_callback(FL_REASON_CHANGED);
+      }
+      return 1;
+  }
+  return Fl_Input::handle(event);
+}
diff --git a/fluid/custom_widgets.h b/fluid/custom_widgets.h
index 8a464ae82..36abc1414 100644
--- a/fluid/custom_widgets.h
+++ b/fluid/custom_widgets.h
@@ -83,6 +83,8 @@ public:
     vars_ = vars;
     vars_user_data_ = user_data;
   }
+
+  int handle(int) override;
 };
 
 #endif
diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 744b831d7..3927ebb45 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -991,8 +991,13 @@ static void cocoaMouseWheelHandler(NSEvent *theEvent)
   Fl::first_window(window);
   // Under OSX, mousewheel deltas are floats, but fltk only supports ints.
   float s = Fl::screen_driver()->scale(0);
-  int dx = roundf([theEvent deltaX] / s);
-  int dy = roundf([theEvent deltaY] / s);
+  float edx = [theEvent deltaX];
+  float edy = [theEvent deltaY];
+  int dx = roundf(edx / s);
+  int dy = roundf(edy / s);
+  // make sure that even small wheel movements count at least as one unit
+  if (edx>0.0f) dx++; else if (edx<0.0f) dx--;
+  if (edy>0.0f) dy++; else if (edy<0.0f) dy--;
   // allow both horizontal and vertical movements to be processed by the widget
   if (dx) {
     Fl::e_dx = -dx;