Use logarithmic scale for speed slider (should allow better speed adjustments)

src/timeline2/view/dialogs/speeddialog.cpp

 #include "speeddialog.h"
 #include "ui_clipspeed_ui.h"
 #include <QPushButton>
+#include <QDebug>
+#include <QtMath>
 
 SpeedDialog::SpeedDialog(QWidget *parent, double speed, double minSpeed, double maxSpeed, bool reversed)
     : QDialog(parent)
@@ -11,11 +13,9 @@ SpeedDialog::SpeedDialog(QWidget *parent, double speed, double minSpeed, double
     ui->speedSpin->setDecimals(2);
     ui->speedSpin->setMinimum(minSpeed);
     ui->speedSpin->setMaximum(maxSpeed);
-    ui->speedSlider->setMinimum(100 * minSpeed);
-    ui->speedSlider->setMaximum(qMin(100 * minSpeed + 100000, 100 *maxSpeed));
-    ui->speedSpin->setValue(speed);
-    ui->speedSlider->setValue(100 * speed);
-    ui->speedSlider->setTickInterval((ui->speedSlider->maximum() - ui->speedSlider->minimum()) / 10);
+    ui->speedSlider->setMinimum(0);
+    ui->speedSlider->setMaximum(100);
+    ui->speedSlider->setTickInterval(10);
     ui->speedSpin->selectAll();
     ui->label_dest->setVisible(false);
     ui->kurlrequester->setVisible(false);
@@ -23,13 +23,18 @@ SpeedDialog::SpeedDialog(QWidget *parent, double speed, double minSpeed, double
     if (reversed) {
         ui->checkBox->setChecked(true);
     }
+    ui->speedSpin->setValue(speed);
+    ui->speedSlider->setValue(qLn(speed) * 12);
     connect(ui->speedSpin, static_cast<void (QDoubleSpinBox::*)(double)>(&QDoubleSpinBox::valueChanged), [&] (double value) {
-        ui->speedSlider->setValue(100 * value);
+        QSignalBlocker bk(ui->speedSlider);
+        ui->speedSlider->setValue(qLn(value) * 12);
         ui->buttonBox->button((QDialogButtonBox::Ok))->setEnabled(!qFuzzyIsNull(value));
     });
     connect(ui->speedSlider, &QSlider::valueChanged, [&] (int value) {
-        ui->speedSpin->setValue(value / 100.);
-        ui->buttonBox->button((QDialogButtonBox::Ok))->setEnabled(value != 0);
+        double res = qExp(value / 12.);
+        QSignalBlocker bk(ui->speedSpin);
+        ui->speedSpin->setValue(res);
+        ui->buttonBox->button((QDialogButtonBox::Ok))->setEnabled(!qFuzzyIsNull(ui->speedSpin->value()));
     });
 }