[core] Cleanup Transform::rotateBy

Make use of PrecisionPoint's operator functionalities inherited from
vec2<> and reduced overhead eg. offset_y is always 0 so no need to add
this to calculation inside the if.

1 files changed, 12 insertions, 17 deletions

diff --git a/src/mbgl/map/transform.cpp b/src/mbgl/map/transform.cpp
index b932c8cb38..3c451d00eb 100644
--- a/src/mbgl/map/transform.cpp
+++ b/src/mbgl/map/transform.cpp
@@ -310,29 +310,24 @@ void Transform::rotateBy(const PrecisionPoint& first, const PrecisionPoint& seco
         return;
     }
 
-    double center_x = static_cast<double>(state.width) / 2.0, center_y = static_cast<double>(state.height) / 2.0;
+    PrecisionPoint center(state.width, state.height);
+    center /= 2;
 
-    const double begin_center_x = first.x - center_x;
-    const double begin_center_y = first.y - center_y;
-
-    const double beginning_center_dist =
-        std::sqrt(begin_center_x * begin_center_x + begin_center_y * begin_center_y);
+    const PrecisionPoint offset = first - center;
+    const double distance = std::sqrt(std::pow(2, offset.x) + std::pow(2, offset.y));
 
     // If the first click was too close to the center, move the center of rotation by 200 pixels
     // in the direction of the click.
-    if (beginning_center_dist < 200) {
-        const double offset_x = -200, offset_y = 0;
-        const double rotate_angle = std::atan2(begin_center_y, begin_center_x);
-        const double rotate_angle_sin = std::sin(rotate_angle);
-        const double rotate_angle_cos = std::cos(rotate_angle);
-        center_x = first.x + rotate_angle_cos * offset_x - rotate_angle_sin * offset_y;
-        center_y = first.y + rotate_angle_sin * offset_x + rotate_angle_cos * offset_y;
+    if (distance < 200) {
+        const double heightOffset = -200;
+        const double rotateAngle = std::atan2(offset.y, offset.x);
+        center.x = first.x + std::cos(rotateAngle) * heightOffset;
+        center.y = first.y + std::sin(rotateAngle) * heightOffset;
     }
 
-    const double first_x = first.x - center_x, first_y = first.y - center_y;
-    const double second_x = second.x - center_x, second_y = second.y - center_y;
-
-    const double ang = state.angle + util::angle_between(first_x, first_y, second_x, second_y);
+    const PrecisionPoint newFirst = first - center;
+    const PrecisionPoint newSecond = second - center;
+    const double ang = state.angle + util::angle_between(newFirst.x, newFirst.y, newSecond.x, newSecond.y);
 
     _setAngle(ang, duration);
 }