clean up "static" and "constexpr" types

- use `static constexpr inline' to avoid requiring
  explicit declarations in object code
- use `const Foo* const' to maybe put into readonly
  binary segment (at least for ELF DSOs)
- `constexpr' in function scope has storage, avoid
  `static'
- don't use `constexpr' where there's no advantage,
  like arrays

We'd like to avoid overhead of atomic initialization
for each function call. No idea how `static constexpr'
requiring storage in the standard plays with atomic
initialization requirement. Hearsay points that
`constexpr' without `static' in block scope behaves
more to our liking. It's all hazy though.

I'm not 100% sure if `static inline constexpr' has any
storage. Hopefully none, like a #define, and stuff
bigger than registers gets coalesced within the same
module, with small stuff being immediates.

3 files changed, 3 insertions, 4 deletions

diff --git a/spline/spline-widget.cpp b/spline/spline-widget.cpp
index b797a907..638b67a7 100644
--- a/spline/spline-widget.cpp
+++ b/spline/spline-widget.cpp
@@ -223,7 +223,7 @@ void spline_widget::drawFunction()
 
     painter.drawPath(path);
 #else
-    static constexpr int line_length_pixels = 3;
+    constexpr int line_length_pixels = 3;
     const qreal max = _config->maxInput();
     const qreal step = clamp(line_length_pixels / c.x(), 5e-2, max);
     QPointF prev = point_to_pixel(QPoint(0, 0));
diff --git a/spline/spline.cpp b/spline/spline.cpp
index 823fd64f..fc77bf8b 100644
--- a/spline/spline.cpp
+++ b/spline/spline.cpp
@@ -27,8 +27,6 @@
 
 using namespace spline_detail;
 
-constexpr std::size_t spline::value_count;
-
 spline::spline(const QString& name, const QString& axis_name, Axis axis) :
     axis(axis)
 {
diff --git a/spline/spline.hpp b/spline/spline.hpp
index 0d080cef..a3532855 100644
--- a/spline/spline.hpp
+++ b/spline/spline.hpp
@@ -16,6 +16,7 @@ using namespace options;
 
 #include "export.hpp"
 
+#include <cstddef>
 #include <vector>
 #include <limits>
 #include <memory>
@@ -102,7 +103,7 @@ class OTR_SPLINE_EXPORT spline : public base_spline
     std::shared_ptr<spline_detail::settings> s;
     QMetaObject::Connection connection, conn_maxx, conn_maxy;
 
-    static constexpr std::size_t value_count = 4096;
+    static constexpr inline std::size_t value_count = 4096;
 
     std::vector<float> data = std::vector<float>(value_count, float(-16));