Use wheel event type instead of deprected mousewheel (#9971)

Fixes the velocity detection problem mentioned in #9671 and #8806.

This is a bit more direct than
https://gwt-review.googlesource.com/c/gwt/+/3171 as it removes the
deprecated events where possible.

Tested in FF and Chrome using a mouse.

Fixes #8009

Author: zbynek

user/src/com/google/gwt/dom/client/BrowserEvents.java

@@ -53,7 +53,9 @@ public class BrowserEvents {
   public static final String MOUSEOUT = "mouseout";
   public static final String MOUSEOVER = "mouseover";
   public static final String MOUSEUP = "mouseup";
+  @Deprecated
   public static final String MOUSEWHEEL = "mousewheel";
+  public static final String WHEEL = "wheel";
   public static final String PROGRESS = "progress";
   public static final String SCROLL = "scroll";
   public static final String TOUCHCANCEL = "touchcancel";

user/src/com/google/gwt/dom/client/DOMImpl.java

@@ -138,7 +138,9 @@ public native boolean eventGetMetaKey(NativeEvent evt) /*-{
     return !!evt.metaKey;
   }-*/;
 
-  public abstract int eventGetMouseWheelVelocityY(NativeEvent evt);
+  public int eventGetMouseWheelVelocityY(NativeEvent evt) {
+    return (int) Math.signum(evt.getDeltaY());
+  }
 
   public abstract EventTarget eventGetRelatedTarget(NativeEvent nativeEvent);
 

user/src/com/google/gwt/dom/client/DOMImplMozilla.java

@@ -124,11 +124,6 @@ public NativeEvent createKeyPressEvent(Document doc, boolean ctrlKey,
         shiftKey, metaKey, 0, charCode);
   }
 
-  @Override
-  public native int eventGetMouseWheelVelocityY(NativeEvent evt) /*-{
-    return evt.detail || 0;
-  }-*/;
-
   @Override
   public native EventTarget eventGetRelatedTarget(NativeEvent evt) /*-{
     // Hack around Mozilla bug 497780 (relatedTarget sometimes returns XUL

user/src/com/google/gwt/dom/client/DOMImplStandardBase.java

@@ -204,11 +204,6 @@ public native EventTarget eventGetCurrentTarget(NativeEvent event) /*-{
     return event.currentTarget || $wnd;
   }-*/;
 
-  @Override
-  public native int eventGetMouseWheelVelocityY(NativeEvent evt) /*-{
-    return Math.round(-evt.wheelDelta / 40) || 0;
-  }-*/;
-
   @Override
   public int getAbsoluteLeft(Element elem) {
     ClientRect rect = getBoundingClientRect(elem);

user/src/com/google/gwt/dom/client/NativeEvent.java

@@ -158,23 +158,40 @@ public final boolean getMetaKey() {
   }
 
   /**
-   * Gets the velocity of the mouse wheel associated with the event along the Y
+   * Gets the sign of the velocity of the mouse wheel associated with the event along the Y
    * axis.
    * <p>
-   * The velocity of the event is an artificial measurement for relative
-   * comparisons of wheel activity. It is affected by some non-browser factors,
-   * including choice of input hardware and mouse acceleration settings. The
-   * sign of the velocity measurement agrees with the screen coordinate system;
-   * negative values are towards the origin and positive values are away from
-   * the origin. Standard scrolling speed is approximately ten units per event.
+   * In previous versions of GWT this returned the velocity normalized to a small integer.
+   * Unfortunately for some devices such normalization rounded non-trivial velocities to 0.
+   * To maintain compatibility with that implementation, this still returns an integer,
+   * but using the sign function
    * </p>
    * 
-   * @return The velocity of the mouse wheel.
+   * @return The velocity of the mouse wheel: -1 for scrolling up, 1 for scrolling down,
+   *         0 if not scrolled at all
+   * @deprecated use getDeltaY() instead
    */
+  @Deprecated
   public final int getMouseWheelVelocityY() {
     return DOMImpl.impl.eventGetMouseWheelVelocityY(this);
   }
 
+  /**
+   * Gets the native velocity of the mouse wheel in Y direction.
+   * @return The velocity of the mouse wheel
+   */
+  public final native double getDeltaY() /*-{
+    return this.deltaY;
+  }-*/;
+
+  /**
+   * Gets the native velocity of the mouse wheel in X direction.
+   * @return The velocity of the mouse wheel
+   */
+  public final native double getDeltaX() /*-{
+    return this.deltaX;
+  }-*/;
+
   /**
    * Gets the related target for this event.
    * 

user/src/com/google/gwt/event/dom/client/MouseWheelEvent.java

@@ -27,16 +27,7 @@ public class MouseWheelEvent extends MouseEvent<MouseWheelHandler> {
    * this event.
    */
   private static final Type<MouseWheelHandler> TYPE = new Type<MouseWheelHandler>(
-      BrowserEvents.MOUSEWHEEL, new MouseWheelEvent());
-
-  static {
-    /**
-     * Hidden type used to ensure DOMMouseScroll gets registered in the type map.
-     * This is the special name used on Mozilla browsers for what everyone else
-     * calls 'mousewheel'.
-     */
-    new Type<MouseWheelHandler>("DOMMouseScroll", new MouseWheelEvent());
-  }
+      BrowserEvents.WHEEL, new MouseWheelEvent());
 
   /**
    * Gets the event type associated with mouse wheel events.
@@ -61,18 +52,30 @@ public final Type<MouseWheelHandler> getAssociatedType() {
   }
 
   /**
-   * Get the change in the mouse wheel position along the Y-axis; negative if
-   * the mouse wheel is moving north (toward the top of the screen) or positive
+   * Get the sign of the change in the mouse wheel position along the Y-axis; -1 if
+   * the mouse wheel is moving north (toward the top of the screen) or 1
    * if the mouse wheel is moving south (toward the bottom of the screen).
    * 
-   * Note that delta values are not normalized across browsers or OSes.
-   * 
-   * @return the delta of the mouse wheel along the y axis
+   * @return the sign of the delta of the mouse wheel along the y axis
+   * @deprecated use getNativeDeltaY() instead
    */
+  @Deprecated
   public int getDeltaY() {
     return getNativeEvent().getMouseWheelVelocityY();
   }
 
+  /**
+   * Get the change in the mouse wheel position along the Y-axis; -1 if
+   * the mouse wheel is moving north (toward the top of the screen) or 1
+   * if the mouse wheel is moving south (toward the bottom of the screen).
+   * Note that the return values are not normalized for browsers and OSs.
+   *
+   * @return the sign of the delta of the mouse wheel along the y axis
+   */
+  public double getNativeDeltaY() {
+    return getNativeEvent().getDeltaY();
+  }
+
   /**
    * Convenience method that returns <code>true</code> if {@link #getDeltaY()}
    * is a negative value (ie, the velocity is directed toward the top of the
@@ -81,7 +84,7 @@ public int getDeltaY() {
    * @return true if the velocity is directed toward the top of the screen
    */
   public boolean isNorth() {
-    return getDeltaY() < 0;
+    return getNativeDeltaY() < 0;
   }
 
   /**
@@ -92,7 +95,7 @@ public boolean isNorth() {
    * @return true if the velocity is directed toward the bottom of the screen
    */
   public boolean isSouth() {
-    return getDeltaY() > 0;
+    return getNativeDeltaY() > 0;
   }
 
   @Override

user/src/com/google/gwt/user/client/impl/DOMImpl.java

@@ -102,7 +102,7 @@ public native int eventGetTypeInt(String eventType) /*-{
     case "scroll": return 0x04000;
     case "error": return 0x10000;
     case "mousewheel": return 0x20000;
-    case "DOMMouseScroll": return 0x20000;
+    case "wheel": return 0x20000;
     case "contextmenu": return 0x40000;
     case "paste": return 0x80000;
     case "touchstart": return 0x100000;

user/src/com/google/gwt/user/client/impl/DOMImplMozilla.java

@@ -15,36 +15,11 @@
  */
 package com.google.gwt.user.client.impl;
 
-import com.google.gwt.dom.client.Element;
-
 /**
  * Mozilla implementation of StandardBrowser.
  */
 class DOMImplMozilla extends DOMImplStandard {
 
-  static {
-    addMozillaCaptureEventDispatchers();
-  }
-
-  @SuppressWarnings("deprecation")
-  private static native void addMozillaCaptureEventDispatchers() /*-{
-    @com.google.gwt.user.client.impl.DOMImplStandard::captureEventDispatchers['DOMMouseScroll'] =
-        @com.google.gwt.user.client.impl.DOMImplStandard::dispatchCapturedMouseEvent(*);
-  }-*/;
-
-  @Override
-  public void sinkEvents(Element elem, int bits) {
-    super.sinkEvents(elem, bits);
-    sinkEventsMozilla(elem, bits);
-  }
-
-  @SuppressWarnings("deprecation")
-  public native void sinkEventsMozilla(Element elem, int bits) /*-{
-    if (bits & 0x20000) {
-      elem.addEventListener('DOMMouseScroll', @com.google.gwt.user.client.impl.DOMImplStandard::dispatchEvent, false);
-    }
-  }-*/;
-
   @Override
   protected void initEventSystem() {
     super.initEventSystem();

user/src/com/google/gwt/user/client/impl/DOMImplStandard.java

@@ -292,7 +292,7 @@ protected native void sinkEventsImpl(Element elem, int bits) /*-{
         @com.google.gwt.user.client.impl.DOMImplStandard::dispatchUnhandledEvent : null;
     if (chMask & 0x10000) elem.onerror       = (bits & 0x10000) ?
         @com.google.gwt.user.client.impl.DOMImplStandard::dispatchEvent : null;
-    if (chMask & 0x20000) elem.onmousewheel  = (bits & 0x20000) ?
+    if (chMask & 0x20000) elem.onwheel       = (bits & 0x20000) ?
         @com.google.gwt.user.client.impl.DOMImplStandard::dispatchEvent : null;
     if (chMask & 0x40000) elem.oncontextmenu = (bits & 0x40000) ?
         @com.google.gwt.user.client.impl.DOMImplStandard::dispatchEvent : null;