According to Qt creator flame graph, call QSettings take lot of time.
When loading the element collection, each items of the collection get
the current language by calling the function QString
QETApp::langFromSetting().
This function instantiate a QSettings object each time and take a lot of
time.
Now the QSettings is instantiate only at the first call, and the value
is stored in memory, then all other call of the function don't
instantiate a QSettings, but just return the value in memory.
Filter "is empty" don't work for any case :
We must to filter for NULL and empty string then replace the sql
sentence "value IS NULL" by "(value IS NULL OR value = '')"
the filter "is not empty" in nomenclature don't work for every case.
Replace SQL sentence "IS NULL" by "!= ''" because an empty string is not
a NULL value string, but a NULL value string is like an empty string
Fix an unwanted behavior when the properties dock widget is displayed :
1 there is no selection
2 the dock widget width is set to minimum
3 select a part, the dock widget gain new widgets used to edit the
current selected part and the width of the dock grow so the width of the
QGraphicsView is reduced and cause a mouse move event.
When this case occur the part is moved but they should not.
Because on windows MachineInfo take a little time to init, we make it to
a singleton.
MachineInfo is build the first time in main.cpp.
Now all other places where we use MachineInfo (aboutqetdialog and
configdialog) gui don't hang anymore in waiting to MachineInfo finish to
build.
Instead of build machine_info class which take time, only to get the max
width and height of screens, call of methods
Machine_info::i_max_screen_width() and
Machine_info::i_max_screen_height() are now static and compute only
this.
The project properties dialog is now faster because don't wait the end
build of machine_info.
