4 files changed, 35 insertions, 18 deletions

diff --git a/src/lib/platform/OSXScreen.h b/src/lib/platform/OSXScreen.h
index 27cb7df..6178529 100644
--- a/src/lib/platform/OSXScreen.h
+++ b/src/lib/platform/OSXScreen.h
@@ -144,10 +144,10 @@ private:
     ButtonID            mapMacButtonToBarrier(UInt16) const;
 
     // map mac scroll wheel value to a barrier scroll wheel value
-    SInt32                mapScrollWheelToBarrier(SInt32) const;
+    SInt32                mapScrollWheelToBarrier(float) const;
 
     // map barrier scroll wheel value to a mac scroll wheel value
-    SInt32                mapScrollWheelFromBarrier(SInt32) const;
+    SInt32                mapScrollWheelFromBarrier(float) const;
 
     // get the current scroll wheel speed
     double                getScrollSpeed() const;
diff --git a/src/lib/platform/OSXScreen.mm b/src/lib/platform/OSXScreen.mm
index 1d80521..1e0268e 100644
--- a/src/lib/platform/OSXScreen.mm
+++ b/src/lib/platform/OSXScreen.mm
@@ -1421,7 +1421,7 @@ OSXScreen::mapMacButtonToBarrier(UInt16 macButton) const
 }
 
 SInt32
-OSXScreen::mapScrollWheelToBarrier(SInt32 x) const
+OSXScreen::mapScrollWheelToBarrier(float x) const
 {
 	// return accelerated scrolling but not exponentially scaled as it is
 	// on the mac.
@@ -1430,7 +1430,7 @@ OSXScreen::mapScrollWheelToBarrier(SInt32 x) const
 }
 
 SInt32
-OSXScreen::mapScrollWheelFromBarrier(SInt32 x) const
+OSXScreen::mapScrollWheelFromBarrier(float x) const
 {
 	// use server's acceleration with a little boost since other platforms
 	// take one wheel step as a larger step than the mac does.
@@ -1948,9 +1948,9 @@ OSXScreen::handleCGInputEvent(CGEventTapProxy proxy,
 			break;
 		case kCGEventScrollWheel:
 			screen->onMouseWheel(screen->mapScrollWheelToBarrier(
-								 CGEventGetIntegerValueField(event, kCGScrollWheelEventDeltaAxis2)),
+								 CGEventGetIntegerValueField(event, kCGScrollWheelEventFixedPtDeltaAxis2) / 65536.0f),
 								 screen->mapScrollWheelToBarrier(
-								 CGEventGetIntegerValueField(event, kCGScrollWheelEventDeltaAxis1)));
+								 CGEventGetIntegerValueField(event, kCGScrollWheelEventFixedPtDeltaAxis1) / 65536.0f));
 			break;
 		case kCGEventKeyDown:
 		case kCGEventKeyUp:
diff --git a/src/lib/platform/XWindowsScreen.cpp b/src/lib/platform/XWindowsScreen.cpp
index 581c911..2846412 100644
--- a/src/lib/platform/XWindowsScreen.cpp
+++ b/src/lib/platform/XWindowsScreen.cpp
@@ -99,6 +99,7 @@ XWindowsScreen::XWindowsScreen(
 		IEventQueue* events) :
 	m_isPrimary(isPrimary),
 	m_mouseScrollDelta(mouseScrollDelta),
+    m_accumulatedScroll(0),
 	m_display(NULL),
 	m_root(None),
 	m_window(None),
@@ -865,9 +866,11 @@ XWindowsScreen::fakeMouseWheel(SInt32, SInt32 yDelta) const
 		return;
 	}
 
-	// choose button depending on rotation direction
-	const unsigned int xButton = mapButtonToX(static_cast<ButtonID>(
-												(yDelta >= 0) ? -1 : -2));
+    int numEvents = accumulateMouseScroll(yDelta);
+
+    // choose button depending on rotation direction
+    const unsigned int xButton = mapButtonToX(static_cast<ButtonID>(
+												(numEvents >= 0) ? -1 : -2));
 	if (xButton == 0) {
 		// If we get here, then the XServer does not support the scroll
 		// wheel buttons, so send PageUp/PageDown keystrokes instead.
@@ -886,20 +889,14 @@ XWindowsScreen::fakeMouseWheel(SInt32, SInt32 yDelta) const
 		return;
 	}
 
-	// now use absolute value of delta
-	if (yDelta < 0) {
-		yDelta = -yDelta;
-	}
-
-	if (yDelta < m_mouseScrollDelta) {
-		LOG((CLOG_WARN "Wheel scroll delta (%d) smaller than threshold (%d)", yDelta, m_mouseScrollDelta));
-	}
+    numEvents = std::abs(numEvents);
 
 	// send as many clicks as necessary
-	for (; yDelta >= m_mouseScrollDelta; yDelta -= m_mouseScrollDelta) {
+    for (; numEvents > 0; numEvents--) {
 		XTestFakeButtonEvent(m_display, xButton, True, CurrentTime);
 		XTestFakeButtonEvent(m_display, xButton, False, CurrentTime);
 	}
+
 	XFlush(m_display);
 }
 
@@ -1643,6 +1640,15 @@ XWindowsScreen::onMouseMove(const XMotionEvent& xmotion)
 	}
 }
 
+int
+XWindowsScreen::accumulateMouseScroll(SInt32 yDelta) const
+{
+    m_accumulatedScroll += yDelta;
+    int numEvents = m_accumulatedScroll / m_mouseScrollDelta;
+    m_accumulatedScroll -= numEvents * m_mouseScrollDelta;
+    return numEvents;
+}
+
 Cursor
 XWindowsScreen::createBlankCursor() const
 {
diff --git a/src/lib/platform/XWindowsScreen.h b/src/lib/platform/XWindowsScreen.h
index 35f9368..a2e3495 100644
--- a/src/lib/platform/XWindowsScreen.h
+++ b/src/lib/platform/XWindowsScreen.h
@@ -136,6 +136,10 @@ private:
     void                onMouseRelease(const XButtonEvent&);
     void                onMouseMove(const XMotionEvent&);
 
+    // Returns the number of scroll events needed after the current delta has
+    // been taken into account
+    int                 accumulateMouseScroll(SInt32 yDelta) const;
+
     bool                detectXI2();
 #ifdef HAVE_XI2
     void                selectXIRawMotion();
@@ -172,8 +176,15 @@ private:
 
     // true if screen is being used as a primary screen, false otherwise
     bool                m_isPrimary;
+
+    // The size of a smallest supported scroll event, in points
     int                 m_mouseScrollDelta;
 
+    // Accumulates scrolls of less than m_mouseScrollDelta across multiple
+    // scroll events. We dispatch a scroll event whenever the accumulated scroll
+    // becomes larger than m_mouseScrollDelta
+    mutable int         m_accumulatedScroll;
+
     Display*            m_display;
     Window                m_root;
     Window                m_window;