exposure: use locale independent float conversion

[simonschmeisser]

std::to_string (and the inverse std::stod) will use the active c locale. Qt apps do this somewhere deep inside. This resulted in the step size being printed as "0,166", which was parsed by the consumer as "0" on systems using , as decimal separator (eg LANG=de)

I could also copy the conversion functions from here https://github.com/ros-planning/moveit/blob/master/moveit_core/utils/src/lexical_casts.cpp (with a suitable namespace) and use them, what do you prefer?

[simonschmeisser]

Full parameter output before was (linebreaks added for clarity):

antibanding-values=off,50hz,60hz,auto;
preview-fps-range-values=(15,15),(15,30),(30,30),(15,60),(60,60),(15,120),(120,120);
preview-frame-rate=30;
min-exposure-compensation=-12;
max-exposure-compensation=12;
exposure-compensation-step=0,166667;
focus-mode-values=infinity,auto,macro,continuous-video,continuous-picture;
effect-values=none,mono,negative,solarize,sepia,posterize,aqua,blackboard,whiteboard;
scene-mode-values=auto,auto,action,portrait,landscape,night,night-portrait,theatre,beach,snow,sunset,fireworks,sports,party,candlelight,hdr;
whitebalance-values=auto,incandescent,fluorescent,warm-fluorescent,daylight,cloudy-daylight,twilight,shade,;
max-num-focus-areas0;
max-num-metering-areas1;
auto-exposure-lock-supported=true;
auto-exposure-lock=false;
auto-whitebalance-lock-supported=true;
auto-whitebalance-lock=false;
flash-mode-values=off,auto,on,torch;
picture-size-values=4000x3000,3840x2160,3264x2448,3200x2400,2976x2976,2688x1512,2592x1944,2048x1536,1920x1440,1920x1080,1600x1200,1440x1080,1280x96

[simonschmeisser]

There is another remaining issue: sailfish-camera remembers the exposure correction but does not initially set it. So if I set it to -2, then close and restart the app it will display -2 but the image will be at 0. Can be "fixed" by moving around the slider but looks unprofessional

[simonschmeisser]

Not sure if you're notified automatically so ping @mlehtima