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From 5ade494a9966c7a9675af86dc42aca62fb4d806d Mon Sep 17 00:00:00 2001
From: Tom Anderson <thomasanderson@chromium.org>
Date: Wed, 21 Oct 2020 22:02:35 +0000
Subject: [PATCH] [XProto] Fix underflow in Fp1616ToDouble
x11::Input::Fp1616 should be treated as a signed integer, otherwise
-1 will underflow to 65535. When dragging a scrollbar, this would
cause the scrollbar to snap to the bottom when the cursor is dragged
above the window's y=0 coordinate. Verified that the issue is fixed
after this CL.
BUG=1139623,1136352
R=sky
Change-Id: Ie318006ceadde9b9ce3e267fb453ddeba0e81da0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485620
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819538}
---
ui/events/x/events_x_utils.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/ui/events/x/events_x_utils.cc b/ui/events/x/events_x_utils.cc
index 3010db5f40c..856dfb221e7 100644
--- ui/events/x/events_x_utils.cc
+++ ui/events/x/events_x_utils.cc
@@ -376,7 +376,7 @@ base::TimeTicks TimeTicksFromXEvent(const x11::Event& xev) {
// This is ported from libxi's FP1616toDBL in XExtInt.c
double Fp1616ToDouble(x11::Input::Fp1616 x) {
- auto x32 = static_cast<uint32_t>(x);
+ auto x32 = static_cast<int32_t>(x);
return x32 * 1.0 / (1 << 16);
}
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