remove const correctness violations

This is possibly related to a livelock where several threads do const
removal in their respective code paths.

Use the `mutable' specifier for the mutexes and spline's cached data.

Now using the `mutable' specifier, get rid of <optional> in
compat/mutex.

2 files changed, 16 insertions, 32 deletions

diff --git a/spline/spline.cpp b/spline/spline.cpp
index 752e85d1..9b0147a8 100644
--- a/spline/spline.cpp
+++ b/spline/spline.cpp
@@ -75,11 +75,6 @@ float spline::get_value(double x)
 
 float spline::get_value_no_save(double x) const
 {
-    return const_cast<spline&>(*this).get_value_no_save_internal(x);
-}
-
-float spline::get_value_no_save_internal(double x)
-{
     QMutexLocker foo(&_mutex);
 
     float  q  = float(x * bucket_size_coefficient(points));
@@ -98,7 +93,7 @@ bool spline::get_last_value(QPointF& point)
     return activep;
 }
 
-float spline::get_value_internal(int x)
+float spline::get_value_internal(int x) const
 {
     if (!validp)
     {
@@ -112,12 +107,6 @@ float spline::get_value_internal(int x)
     return sign * clamp(ret_, 0, 1000);
 }
 
-void spline::add_lone_point()
-{
-    points = { QPointF(s->opts.clamp_x_, s->opts.clamp_y_) };
-    s->points = points;
-}
-
 QPointF spline::ensure_in_bounds(const QList<QPointF>& points, int i)
 {
     const int sz = points.size();
@@ -148,7 +137,7 @@ bool spline::sort_fn(const QPointF& one, const QPointF& two)
     return one.x() < two.x();
 }
 
-void spline::update_interp_data()
+void spline::update_interp_data() const
 {
     points_t list = points;
     ensure_valid(list);
@@ -208,7 +197,7 @@ void spline::update_interp_data()
             };
 
             // multiplier helps fill in all the x's needed
-            const unsigned end = int(c_interp * (p2_x - p1_x)) + 1;
+            const unsigned end{int(c_interp * (p2_x - p1_x)) + 1u};
 
             for (unsigned k = 0; k <= end; k++)
             {
@@ -363,7 +352,7 @@ double spline::max_output() const
     return std::fabs(clamp.to<double>());
 }
 
-void spline::ensure_valid(points_t& list)
+void spline::ensure_valid(points_t& list) const
 {
     QMutexLocker foo(&_mutex);
 
diff --git a/spline/spline.hpp b/spline/spline.hpp
index 3d2d6e57..acac2ad7 100644
--- a/spline/spline.hpp
+++ b/spline/spline.hpp
@@ -8,12 +8,10 @@
 
 #pragma once
 
-#include "compat/copyable-mutex.hpp"
 #include "options/options.hpp"
-
 #include "axis-opts.hpp"
-
 #include "export.hpp"
+#include "compat/copyable-mutex.hpp"
 
 #include <cstddef>
 #include <vector>
@@ -95,10 +93,8 @@ struct OTR_SPLINE_EXPORT base_spline : base_spline_, spline_modify_mixin, spline
 class OTR_SPLINE_EXPORT spline : public base_spline
 {
     double bucket_size_coefficient(const QList<QPointF>& points) const;
-    void update_interp_data();
-    float get_value_internal(int x);
-    void add_lone_point();
-    float get_value_no_save_internal(double x);
+    void update_interp_data() const;
+    float get_value_internal(int x) const;
     static bool sort_fn(const QPointF& one, const QPointF& two);
 
     static QPointF ensure_in_bounds(const QList<QPointF>& points, int i);
@@ -106,21 +102,20 @@ class OTR_SPLINE_EXPORT spline : public base_spline
 
     void disconnect_signals();
 
+    mutex _mutex { mutex::Recursive };
     std::shared_ptr<spline_detail::settings> s;
     QMetaObject::Connection conn_changed, conn_maxx, conn_maxy;
+    mutable std::vector<float> data = std::vector<float>(value_count, float(-16));
+    mutable QPointF last_input_value;
+    mutable bool activep = false;
+    mutable bool validp = false;
 
-    static constexpr inline std::size_t value_count = 4096;
-
-    std::vector<float> data = std::vector<float>(value_count, float(-16));
-
-    mutex _mutex { mutex::recursive };
-    QPointF last_input_value;
     std::shared_ptr<QObject> ctx { std::make_shared<QObject>() };
 
-    bool activep = false;
-    bool validp = false;
+    // cached s->points
+    mutable points_t points;
 
-    points_t points;
+    static constexpr inline std::size_t value_count = 4096;
 
 public:
     void invalidate_settings();
@@ -153,7 +148,7 @@ public:
 
     void set_tracking_active(bool value) override;
     bundle get_bundle();
-    void ensure_valid(points_t& in_out);
+    void ensure_valid(points_t& in_out) const;
 
     std::shared_ptr<spline_detail::base_settings> get_settings() override;
     std::shared_ptr<const spline_detail::base_settings> get_settings() const override;