MathUtils: Add exponential interpolation

Change-Id: I58bb26a6e921cbd1f5532bddcd6a6700ff80b94f
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

2 files changed, 23 insertions, 5 deletions

diff --git a/src/libs/utils/mathutils.cpp b/src/libs/utils/mathutils.cpp
index d9e18b18a3..f1bdc5999c 100644
--- a/src/libs/utils/mathutils.cpp
+++ b/src/libs/utils/mathutils.cpp
@@ -39,9 +39,26 @@ int interpolateTangential(int x, int xHalfLife, int y1, int y2)
         return y1;
     if (y1 == y2)
         return y1;
-    const double mapped = atan2(double(x), double(xHalfLife));
-    const double progress = y1 + (y2 - y1) * mapped * 2 / M_PI;
-    return qRound(progress);
+    const double angle = atan2((double)x, (double)xHalfLife);
+    const double result = y1 + (y2 - y1) * angle * 2 / M_PI;
+    return qRound(result);
 }
 
-} // namespace Utils::Math
+/*!
+    Exponential interpolation:
+    For x = 0 it returns y1.
+    For x = xHalfLife it returns 50 % of the distance between y1 and y2.
+    For x = infinity it returns y2.
+*/
+int interpolateExponential(int x, int xHalfLife, int y1, int y2)
+{
+    if (x == 0)
+        return y1;
+    if (y1 == y2)
+        return y1;
+    const double exponent = pow(0.5, (double)x / xHalfLife);
+    const double result = y1 + (y2 - y1) * (1.0 - exponent);
+    return qRound(result);
+}
+
+} // namespace Utils::MathUtils
diff --git a/src/libs/utils/mathutils.h b/src/libs/utils/mathutils.h
index 8a9af9e4e6..21f66ff581 100644
--- a/src/libs/utils/mathutils.h
+++ b/src/libs/utils/mathutils.h
@@ -9,5 +9,6 @@ namespace Utils::MathUtils {
 
 QTCREATOR_UTILS_EXPORT int interpolateLinear(int x, int x1, int x2, int y1, int y2);
 QTCREATOR_UTILS_EXPORT int interpolateTangential(int x, int xHalfLife, int y1, int y2);
+QTCREATOR_UTILS_EXPORT int interpolateExponential(int x, int xHalfLife, int y1, int y2);
 
-} // namespace Utils::Math
+} // namespace Utils::MathUtils