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Howto:Add new fgcommands to FlightGear: Difference between revisions
Howto:Add new fgcommands to FlightGear (view source)
Revision as of 13:02, 10 February 2012
, 10 February 2012→Exception handling
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== Exception handling == | == Exception handling == | ||
To be on the safe side, complex fgcommands should make use of exception handling to catch exceptions and deal with them gracefully, so that they cannot affect the simulator critically. | To be on the safe side, complex fgcommands should make use of exception handling to catch exceptions and deal with them gracefully, so that they cannot affect the simulator critically. | ||
This is accomplished by using standard C++ try/catch blocks, usually catching an sg_exception. The SG_LOG() macro can be used to print debugging information to the console. | |||
For example, see the callback function "do_preferences_load" in [http://gitorious.org/fg/flightgear/blobs/next/src/Main/fg_commands.cxx#line445 line 445]: | |||
<syntaxhighlight lang="cpp"> | |||
/** | |||
* Built-in command: (re)load preferences. | |||
* | |||
* path (optional): the file name to load the panel from (relative | |||
* to FG_ROOT). Defaults to "preferences.xml". | |||
*/ | |||
static bool | |||
do_preferences_load (const SGPropertyNode * arg) | |||
{ | |||
try { | |||
fgLoadProps(arg->getStringValue("path", "preferences.xml"), | |||
globals->get_props()); | |||
} catch (const sg_exception &e) { | |||
guiErrorMessage("Error reading global preferences: ", e); | |||
return false; | |||
} | |||
SG_LOG(SG_INPUT, SG_INFO, "Successfully read global preferences."); | |||
return true; | |||
} | |||
</syntaxhighlight> | |||
= Adding new commands = | = Adding new commands = | ||