Fix Windows mouse wheel scroll speed

In Windows, event dispatching code is throwing out the wheel scroll count value.
Despite of how many fast you move the wheel, it only make one-notch scroll event.

This patch convert wheel event to multiple 1-notch wheel events.

This also correct the handling of smooth scroll mouse wheel (which can report smaller than 1-notch wheel movement) by accumulating the small wheel delta values.

Reviewers: djnz, shadowrom, elubie, #platform:_windows, sergey, juicyfruit, brecht

Reviewed By: shadowrom, elubie, #platform:_windows, brecht

Subscribers: dingto, elubie, brachi, brecht

Differential Revision: https://developer.blender.org/D143

2 files changed, 27 insertions, 20 deletions

diff --git a/intern/ghost/intern/GHOST_SystemWin32.cpp b/intern/ghost/intern/GHOST_SystemWin32.cpp
index 60e7815ccbb..e43634508b7 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.cpp
+++ b/intern/ghost/intern/GHOST_SystemWin32.cpp
@@ -712,18 +712,26 @@ GHOST_EventCursor *GHOST_SystemWin32::processCursorEvent(GHOST_TEventType type,
 }
 
 
-GHOST_EventWheel *GHOST_SystemWin32::processWheelEvent(GHOST_WindowWin32 *window, WPARAM wParam, LPARAM lParam)
+void GHOST_SystemWin32::processWheelEvent(GHOST_WindowWin32 *window, WPARAM wParam, LPARAM lParam)
 {
-	// short fwKeys = LOWORD(wParam);			// key flags
-	int zDelta = (short) HIWORD(wParam);    // wheel rotation
-	
-	// zDelta /= WHEEL_DELTA;
-	// temporary fix below: microsoft now has added more precision, making the above division not work
-	zDelta = (zDelta <= 0) ? -1 : 1;
+	GHOST_SystemWin32 *system = (GHOST_SystemWin32 *)getSystem();
 
-	// short xPos = (short) LOWORD(lParam);	// horizontal position of pointer
-	// short yPos = (short) HIWORD(lParam);	// vertical position of pointer
-	return new GHOST_EventWheel(getSystem()->getMilliSeconds(), window, zDelta);
+	int acc = system->m_wheelDeltaAccum;
+	int delta = GET_WHEEL_DELTA_WPARAM(wParam);
+	
+	if (acc * delta < 0) {
+		// scroll direction reversed.
+		acc = 0;
+	}
+	acc += delta;
+	int direction = (acc >= 0) ? 1 : -1;
+	acc = abs(acc);
+	
+	while (acc >= WHEEL_DELTA) {
+		system->pushEvent(new GHOST_EventWheel(system->getMilliSeconds(), window, direction));
+		acc -= WHEEL_DELTA;
+	}
+	system->m_wheelDeltaAccum = acc * direction;
 }
 
 
@@ -1137,14 +1145,9 @@ LRESULT WINAPI GHOST_SystemWin32::s_wndProc(HWND hwnd, UINT msg, WPARAM wParam,
 					POINT mouse_pos = {GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam)};
 					HWND mouse_hwnd = ChildWindowFromPoint(HWND_DESKTOP, mouse_pos);
 					GHOST_WindowWin32 *mouse_window = (GHOST_WindowWin32 *)::GetWindowLongPtr(mouse_hwnd, GWLP_USERDATA);
-					if (mouse_window != NULL) {
-						event = processWheelEvent(mouse_window, wParam, lParam);
-					}
-					else {
-						/* Happens when mouse is not over any of blender's windows. */
-						event = processWheelEvent(window, wParam, lParam);
-					}
-
+					
+					processWheelEvent(mouse_window ? mouse_window : window , wParam, lParam);
+					eventHandled = true;
 #ifdef BROKEN_PEEK_TOUCHPAD
 					PostMessage(hwnd, WM_USER, 0, 0);
 #endif
@@ -1203,6 +1206,7 @@ LRESULT WINAPI GHOST_SystemWin32::s_wndProc(HWND hwnd, UINT msg, WPARAM wParam,
 					GHOST_ModifierKeys modifiers;
 					modifiers.clear();
 					system->storeModifierKeys(modifiers);
+					system->m_wheelDeltaAccum = 0;
 					event = processWindowEvent(LOWORD(wParam) ? GHOST_kEventWindowActivate : GHOST_kEventWindowDeactivate, window);
 					/* WARNING: Let DefWindowProc handle WM_ACTIVATE, otherwise WM_MOUSEWHEEL
 					 * will not be dispatched to OUR active window if we minimize one of OUR windows. */
diff --git a/intern/ghost/intern/GHOST_SystemWin32.h b/intern/ghost/intern/GHOST_SystemWin32.h
index 3085fde610b..d534a300b35 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.h
+++ b/intern/ghost/intern/GHOST_SystemWin32.h
@@ -264,12 +264,12 @@ protected:
 	static GHOST_EventCursor *processCursorEvent(GHOST_TEventType type, GHOST_WindowWin32 *window);
 
 	/**
-	 * Creates a mouse wheel event.
+	 * Handles a mouse wheel event.
 	 * \param window	The window receiving the event (the active window).
 	 * \param wParam	The wParam from the wndproc
 	 * \param lParam	The lParam from the wndproc
 	 */
-	static GHOST_EventWheel *processWheelEvent(GHOST_WindowWin32 *window, WPARAM wParam, LPARAM lParam);
+	static void processWheelEvent(GHOST_WindowWin32 *window, WPARAM wParam, LPARAM lParam);
 
 	/**
 	 * Creates a key event and updates the key data stored locally (m_modifierKeys).
@@ -376,6 +376,9 @@ protected:
 
 	/** Console status */
 	int m_consoleStatus;
+
+	/** Wheel delta accumulator **/
+	int m_wheelDeltaAccum;
 };
 
 inline void GHOST_SystemWin32::retrieveModifierKeys(GHOST_ModifierKeys& keys) const