Split out the piecewise linear interpolation code into its own class.

[nageru] / nonlinear_fader.cpp

diff --git a/nonlinear_fader.cpp b/nonlinear_fader.cpp
index 4892c6770517b5a8d465fcf9949a808e8332da47..06a929c39259c037a0d6bf27c9a0a36c0ea8efcd 100644 (file)
--- a/nonlinear_fader.cpp
+++ b/nonlinear_fader.cpp
@@ -11,6 +11,8 @@
 #include <utility>
 #include <vector>
 
+#include "piecewise_interpolator.h"
+
 class QPaintEvent;
 class QWidget;
 
@@ -18,7 +20,7 @@ using namespace std;
 
 namespace {
 
-vector<pair<double, double>> fader_control_points = {
+PiecewiseInterpolator interpolator({
        // The main area is from +6 to -12 dB (18 dB), and we use half the slider range for it.
        // Adjust slightly so that the MIDI controller value of 106 becomes exactly 0.0 dB
        // (cf. map_controller_to_float()); otherwise, we'd miss ever so slightly, which is
@@ -37,49 +39,7 @@ vector<pair<double, double>> fader_control_points = {
 
        // -48 to -84 (36 dB) gets half of half of half.
        { -84.0, 0.0 },
-};
-
-double slider_fraction_to_db(double db)
-{
-       if (db >= fader_control_points[0].second) {
-               return fader_control_points[0].first;
-       }
-       if (db <= fader_control_points.back().second) {
-               return fader_control_points.back().first;
-       }
-       for (unsigned i = 1; i < fader_control_points.size(); ++i) {
-               const double x0 = fader_control_points[i].second;
-               const double x1 = fader_control_points[i - 1].second;
-               const double y0 = fader_control_points[i].first;
-               const double y1 = fader_control_points[i - 1].first;
-               if (db >= x0 && db <= x1) {
-                       const double t = (db - x0) / (x1 - x0);
-                       return y0 + t * (y1 - y0);
-               }
-       }
-       assert(false);
-}
-
-double db_to_slider_fraction(double x)
-{
-       if (x >= fader_control_points[0].first) {
-               return fader_control_points[0].second;
-       }
-       if (x <= fader_control_points.back().first) {
-               return fader_control_points.back().second;
-       }
-       for (unsigned i = 1; i < fader_control_points.size(); ++i) {
-               const double x0 = fader_control_points[i].first;
-               const double x1 = fader_control_points[i - 1].first;
-               const double y0 = fader_control_points[i].second;
-               const double y1 = fader_control_points[i - 1].second;
-               if (x >= x0 && x <= x1) {
-                       const double t = (x - x0) / (x1 - x0);
-                       return y0 + t * (y1 - y0);
-               }
-       }
-       assert(false);
-}
+});
 
 }  // namespace
 
@@ -117,7 +77,7 @@ void NonLinearFader::paintEvent(QPaintEvent *event)
        int x_margin = 5;
        p.setPen(Qt::darkGray);
        for (int db = -84; db <= 6; db += 6) {
-               int y = slider_min + lrint(db_to_slider_fraction(db) * (slider_max - slider_min));
+               int y = slider_min + lrint(interpolator.db_to_fraction(db) * (slider_max - slider_min));
                p.drawLine(QPoint(0, y), QPoint(gr.left() - x_margin, y));
                p.drawLine(QPoint(gr.right() + x_margin, y), QPoint(width() - 1, y));
        }
@@ -133,7 +93,7 @@ void NonLinearFader::sliderChange(SliderChange change)
                        db_value = -HUGE_VAL;
                } else {
                        double frac = double(value() - minimum()) / (maximum() - minimum());
-                       db_value = slider_fraction_to_db(frac);
+                       db_value = interpolator.fraction_to_db(frac);
                }
                emit dbValueChanged(db_value);
        }
@@ -142,7 +102,7 @@ void NonLinearFader::sliderChange(SliderChange change)
 void NonLinearFader::update_slider_position()
 {
        inhibit_updates = true;
-       double val = db_to_slider_fraction(db_value) * (maximum() - minimum()) + minimum();
+       double val = interpolator.db_to_fraction(db_value) * (maximum() - minimum()) + minimum();
        setValue(lrint(val));
        inhibit_updates = false;
 }