From c310f7bb803dda17467a353edf903d68c82fcfe4 Mon Sep 17 00:00:00 2001
From: Matt Brubeck <mbrubeck@limpet.net>
Date: Mon, 24 Aug 2015 14:32:31 -0700
Subject: Take XIScrollClassInfo::increment into account

From the "Smooth Scrolling" section of [XI2Proto.txt][1]:

> One unit of scrolling in either direction is considered to be equivalent to
> one button event, e.g. for a unit size of 1.0, -2.0 on an valuator type
> Vertical sends two button press/release events for button 4. Likewise, a
> button press event for button 7 generates an event on the Horizontal
> valuator with a value of +1.0. The server may accumulate deltas of less than
> one unit of scrolling.

From [What's new in XI 2.1 - smooth scrolling][2]:

> The increment defines what delta the driver considers to be one scroll
> event. For an increment of +5, each delta of 5 should be regarded as one
> scroll unit down. For an increment of -3, each delta of 3 should be regarded
> as one scroll unit up (i.e. inverted).

[1]: http://www.x.org/releases/X11R7.7/doc/inputproto/XI2proto.txt
[2]: http://who-t.blogspot.com/2011/09/whats-new-in-xi-21-smooth-scrolling.html

This fixes scrolling with my Microsoft mouse in X11 on Debian 8.1.
---
 src/api/x11/input.rs | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

(limited to 'src/api/x11')

diff --git a/src/api/x11/input.rs b/src/api/x11/input.rs
index 7387ab0..75939e9 100644
--- a/src/api/x11/input.rs
+++ b/src/api/x11/input.rs
@@ -21,7 +21,8 @@ struct Axis {
     id: i32,
     device_id: i32,
     axis_number: i32,
-    axis_type: AxisType
+    axis_type: AxisType,
+    scroll_increment: f64,
 }
 
 #[derive(Debug)]
@@ -167,7 +168,7 @@ impl XInputEventHandler {
         use events::Event::{Focused, MouseInput, MouseMoved, MouseWheel};
         use events::ElementState::{Pressed, Released};
         use events::MouseButton::{Left, Right, Middle};
-        use events::MouseScrollDelta::{PixelDelta, LineDelta};
+        use events::MouseScrollDelta::LineDelta;
         use events::{Touch, TouchPhase};
 
         match cookie.evtype {
@@ -221,7 +222,7 @@ impl XInputEventHandler {
                 }
 
                 if scroll_delta.0.abs() > 0.0 || scroll_delta.1.abs() > 0.0 {
-                    Some(MouseWheel(PixelDelta(scroll_delta.0 as f32, scroll_delta.1 as f32)))
+                    Some(MouseWheel(LineDelta(scroll_delta.0 as f32, scroll_delta.1 as f32)))
                 } else {
                     let new_cursor_pos = (event_data.event_x, event_data.event_y);
                     if new_cursor_pos != self.current_state.cursor_pos {
@@ -290,7 +291,8 @@ fn read_input_axis_info(display: &Arc<XConnection>) -> Vec<Axis> {
                             ffi::XIScrollTypeHorizontal => AxisType::HorizontalScroll,
                             ffi::XIScrollTypeVertical => AxisType::VerticalScroll,
                             _ => { unreachable!() }
-                        }
+                        },
+                        scroll_increment: scroll_class.increment,
                     })
                 },
                 _ => {}
@@ -314,7 +316,7 @@ fn calc_scroll_deltas(event: &ffi::XIDeviceEvent,
             prev_axis.axis_number == axis_id
     });
     let delta = match prev_value_pos {
-        Some(idx) => axis_value - prev_axis_values[idx].value,
+        Some(idx) => prev_axis_values[idx].value - axis_value,
         None => 0.0
     };
 
@@ -335,8 +337,8 @@ fn calc_scroll_deltas(event: &ffi::XIDeviceEvent,
         if axis.id == event.sourceid &&
             axis.axis_number == axis_id {
                 match axis.axis_type {
-                    AxisType::HorizontalScroll => scroll_delta.0 = delta,
-                    AxisType::VerticalScroll => scroll_delta.1 = delta
+                    AxisType::HorizontalScroll => scroll_delta.0 = delta / axis.scroll_increment,
+                    AxisType::VerticalScroll => scroll_delta.1 = delta / axis.scroll_increment
                 }
             }
     }
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