Use constexpr for static const values whenever possible

Signed-off-by: falkTX <falktx@falktx.com>

include/app/common.hpp

@@ -15,8 +15,8 @@ namespace app {
 
 
 // A 1HPx3U module should be 15x380 pixels. Thus the width of a module should be a factor of 15.
-static const float RACK_GRID_WIDTH = 15;
-static const float RACK_GRID_HEIGHT = 380;
+static constexpr const float RACK_GRID_WIDTH = 15;
+static constexpr const float RACK_GRID_HEIGHT = 380;
 static const math::Vec RACK_GRID_SIZE = math::Vec(RACK_GRID_WIDTH, RACK_GRID_HEIGHT);
 static const math::Vec RACK_OFFSET = RACK_GRID_SIZE.mult(math::Vec(2000, 100));
 

include/dsp/common.hpp

@@ -14,9 +14,9 @@ namespace dsp {
 
 // Constants
 
-static const float FREQ_C4 = 261.6256f;
-static const float FREQ_A4 = 440.0000f;
-static const float FREQ_SEMITONE = 1.0594630943592953f;
+static constexpr const float FREQ_C4 = 261.6256f;
+static constexpr const float FREQ_A4 = 440.0000f;
+static constexpr const float FREQ_SEMITONE = 1.0594630943592953f;
 
 // Mathematical functions
 

include/engine/Port.hpp

@@ -8,7 +8,7 @@ namespace engine {
 
 
 /** This is inspired by the number of MIDI channels. */
-static const int PORT_MAX_CHANNELS = 16;
+static constexpr const int PORT_MAX_CHANNELS = 16;
 
 
 struct Port {

include/window/Svg.hpp

@@ -13,8 +13,8 @@ namespace window {
 
 
 /** Arbitrary DPI, standardized for Rack. */
-static const float SVG_DPI = 75.f;
-static const float MM_PER_IN = 25.4f;
+static constexpr const float SVG_DPI = 75.f;
+static constexpr const float MM_PER_IN = 25.4f;
 
 
 /** Converts inch measurements to pixels */