Input: Add smooth-scrolling support to GetPointerEvents

For scroll wheel support, we used to send buttons 4/5 and 6/7 for
horizontal/vertical positive/negative scroll events.  For touchpads, we
really want more fine-grained scroll values.  GetPointerEvents now
accepts both old-school scroll button presses, and new-style scroll axis
events, while emitting both types of events to support both old and new
clients.

This works with the new XIScrollClass to mark axes as scrolling axes.
Drivers mark any valuators that send scroll events with SetScrollValuator.
(Currently missing: the XIDeviceChangeEvent being sent when a driver changes
a scroll axis at run-time. This can be added later.)

Note: the SCROLL_TYPE enums are intentionally different values to the XI2
proto values to avoid copy/overlapping range bugs.

Co-authored-by: Daniel Stone <daniel@fooishbar.org>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>

1 files changed, 166 insertions, 4 deletions

diff --git a/dix/getevents.c b/dix/getevents.c
index 45243df..c429715 100644
--- a/dix/getevents.c
+++ b/dix/getevents.c
@@ -2,6 +2,7 @@
  * Copyright © 2006 Nokia Corporation
  * Copyright © 2006-2007 Daniel Stone
  * Copyright © 2008 Red Hat, Inc.
+ * Copyright © 2011 The Chromium Authors
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -603,8 +604,10 @@ GetMaximumEventsNum(void) {
     /* One raw event
      * One device event
      * One possible device changed event
+     * Lots of possible separate button scroll events (horiz + vert)
+     * Lots of possible separate raw button scroll events (horiz + vert)
      */
-    return 3;
+    return 100;
 }
 
 
@@ -1171,6 +1174,95 @@ fill_pointer_events(InternalEvent *events, DeviceIntPtr pDev, int type,
 }
 
 /**
+ * Generate events for each scroll axis that changed between before/after
+ * for the device.
+ *
+ * @param events The pointer to the event list to fill the events
+ * @param dev The device to generate the events for
+ * @param axis The axis number to generate events for
+ * @param mask State before this event in absolute coords
+ * @param[in,out] last Last scroll state posted in absolute coords (modified
+ * in-place)
+ * @param ms Current time in ms
+ * @param max_events Max number of events to be generated
+ * @return The number of events generated
+ */
+static int
+emulate_scroll_button_events(InternalEvent *events,
+                             DeviceIntPtr dev,
+                             int axis,
+                             const ValuatorMask *mask,
+                             ValuatorMask *last,
+                             CARD32 ms,
+                             int max_events)
+{
+    AxisInfoPtr ax;
+    double delta;
+    double incr;
+    int num_events = 0;
+    double total;
+    int b;
+
+    if (dev->valuator->axes[axis].scroll.type == SCROLL_TYPE_NONE)
+        return 0;
+
+    if (!valuator_mask_isset(mask, axis))
+        return 0;
+
+    ax = &dev->valuator->axes[axis];
+    incr = ax->scroll.increment;
+
+    if (!valuator_mask_isset(last, axis))
+        valuator_mask_set_double(last, axis, 0);
+
+    delta = valuator_mask_get_double(mask, axis) - valuator_mask_get_double(last, axis);
+    total = delta;
+    b = (ax->scroll.type == SCROLL_TYPE_VERTICAL) ? 5 : 7;
+
+    if ((incr > 0 && delta < 0) ||
+        (incr < 0 && delta > 0))
+        b--; /* we're scrolling up or left → button 4 or 6 */
+
+    while (fabs(delta) >= fabs(incr))
+    {
+        int nev_tmp;
+
+        if (delta > 0)
+            delta -= fabs(incr);
+        else if (delta < 0)
+            delta += fabs(incr);
+
+        /* fill_pointer_events() generates four events: one normal and one raw
+         * event for button press and button release.
+         * We may get a bigger scroll delta than we can generate events
+         * for. In that case, we keep decreasing delta, but skip events.
+         */
+        if (num_events + 4 < max_events)
+        {
+            nev_tmp = fill_pointer_events(events, dev, ButtonPress, b, ms,
+                                          POINTER_EMULATED, NULL);
+            events += nev_tmp;
+            num_events += nev_tmp;
+            nev_tmp = fill_pointer_events(events, dev, ButtonRelease, b, ms,
+                                          POINTER_EMULATED, NULL);
+            events += nev_tmp;
+            num_events += nev_tmp;
+        }
+    }
+
+    /* We emulated, update last.scroll */
+    if (total != delta)
+    {
+        total -= delta;
+        valuator_mask_set_double(last, axis,
+                                 valuator_mask_get_double(last, axis) + total);
+    }
+
+    return num_events;
+}
+
+
+/**
  * Generate a complete series of InternalEvents (filled into the EventList)
  * representing pointer motion, or button presses.  If the device is a slave
  * device, also potentially generate a DeviceClassesChangedEvent to update
@@ -1193,7 +1285,12 @@ GetPointerEvents(InternalEvent *events, DeviceIntPtr pDev, int type,
                  int buttons, int flags, const ValuatorMask *mask_in)
 {
     CARD32 ms = GetTimeInMillis();
-    int num_events = 0;
+    int num_events = 0, nev_tmp;
+    int h_scroll_axis = pDev->valuator->h_scroll_axis;
+    int v_scroll_axis = pDev->valuator->v_scroll_axis;
+    ValuatorMask mask;
+    ValuatorMask scroll;
+    int i;
 
     /* refuse events from disabled devices */
     if (!pDev->enabled)
@@ -1204,8 +1301,73 @@ GetPointerEvents(InternalEvent *events, DeviceIntPtr pDev, int type,
 
     events = UpdateFromMaster(events, pDev, DEVCHANGE_POINTER_EVENT,
                               &num_events);
-    num_events += fill_pointer_events(events, pDev, type, buttons, ms, flags,
-                                      mask_in);
+
+    valuator_mask_copy(&mask, mask_in);
+
+    /* Turn a scroll button press into a smooth-scrolling event if
+     * necessary. This only needs to cater for the XIScrollFlagPreferred
+     * axis (if more than one scrolling axis is present) */
+    if (type == ButtonPress)
+    {
+        double val, adj;
+        int axis;
+
+        switch (buttons) {
+        case 4:
+            adj = 1.0;
+            axis = v_scroll_axis;
+            break;
+        case 5:
+            adj = -1.0;
+            axis = v_scroll_axis;
+            break;
+        case 6:
+            adj = 1.0;
+            axis = h_scroll_axis;
+            break;
+        case 7:
+            adj = -1.0;
+            axis = h_scroll_axis;
+            break;
+        default:
+            adj = 0.0;
+            axis = -1;
+            break;
+        }
+
+        if (adj != 0.0 && axis != -1)
+        {
+            adj *= pDev->valuator->axes[axis].scroll.increment;
+            val = valuator_mask_get_double(&mask, axis) + adj;
+            valuator_mask_set_double(&mask, axis, val);
+            type = MotionNotify;
+            buttons = 0;
+        }
+    }
+
+    /* First fill out the original event set, with smooth-scrolling axes. */
+    nev_tmp = fill_pointer_events(events, pDev, type, buttons, ms, flags,
+                                  &mask);
+    events += nev_tmp;
+    num_events += nev_tmp;
+
+    valuator_mask_zero(&scroll);
+
+    /* Now turn the smooth-scrolling axes back into emulated button presses
+     * for legacy clients, based on the integer delta between before and now */
+    for (i = 0; i < valuator_mask_size(&mask); i++) {
+        if (!valuator_mask_isset(&mask, i))
+            continue;
+
+        valuator_mask_set_double(&scroll, i, pDev->last.valuators[i]);
+
+        nev_tmp = emulate_scroll_button_events(events, pDev, i, &scroll,
+                                               pDev->last.scroll, ms,
+                                               GetMaximumEventsNum() - num_events);
+        events += nev_tmp;
+        num_events += nev_tmp;
+    }
+
     return num_events;
 }