Be consistent about values related to pi (radian / degree ratio)

Use JavaScript's Math.PI to compute 180 / pi (the number of degrees in
one radian), rather than a hand-coded value for this constant.  Store
the result in a readonly property double to avoid repeating the
computation.  Tweak the pitch and roll calculations to use more apt
Math methods: use hypot rather than sqrt of a sum of squares, and
use atan2 instead of a tan of a ratio (whose denominator is always
positive, so this doesn't change which angle we get).

Task-number: QTBUG-58083
Change-Id: Ic3f865dfcbd9b02a0b93f065995d850386aef18c
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/examples/sensors/accelbubble/accelbubble.qml b/examples/sensors/accelbubble/accelbubble.qml
index 37bf427..8bd036f 100644
--- a/examples/sensors/accelbubble/accelbubble.qml
+++ b/examples/sensors/accelbubble/accelbubble.qml
@@ -63,7 +63,7 @@ ApplicationWindow {
     width: 320
     height: 480
     visible: true
-
+    readonly property double radians_to_degrees: 180 / Math.PI
 
 //! [1]
     Accelerometer {
@@ -101,10 +101,10 @@ ApplicationWindow {
     }
 
     function calcPitch(x,y,z) {
-        return -(Math.atan(y / Math.sqrt(x * x + z * z)) * 57.2957795);
+        return -Math.atan2(y, Math.hypot(x, z)) * mainWindow.radians_to_degrees;
     }
     function calcRoll(x,y,z) {
-         return -(Math.atan(x / Math.sqrt(y * y + z * z)) * 57.2957795);
+        return -Math.atan2(x, Math.hypot(y, z)) * mainWindow.radians_to_degrees;
     }
 
     Image {