FSX:SE Reading from a File in a C Gauge

[Bitman]

Hey everyone! I'm working on a project right now that involves reading a value from a text file and then displaying it on a gauge. I started working off of the SDK.Fuel.cpp in the SDK sample code to try to get it to work. The gauge loads fine and no errors are sent from FSX, but the gauge never updates. Here is my code:

#include <fstream>
//    Set up gauge header
char fuel_gauge_name[]        = GAUGE_NAME;
extern PELEMENT_HEADER        fuel_list;
extern MOUSERECT            fuel_mouse_rect[];

GAUGE_HEADER_FS700( GAUGE_W, fuel_gauge_name, &fuel_list, \
                        fuel_mouse_rect, 0, 0, 0, 0 );



/////////////////////////////////////////////////////////////////////////////
#define    GAUGE_MIN_FUEL    0
#define    GAUGE_MAX_FUEL    75

NONLINEARITY  fuel_nonlinearity[] =
{
    {{30,    182},     0, 0},
    {{119,     47},    25, 0},
    {{246,     93},    50, 0},
    {{241,    221},    75, 0}
};

//TODO: Add file reading for gauge readout
FLOAT64 FSAPI fuel_needle_cb( PELEMENT_NEEDLE pelement )
{
    static int time = 18;
    static FLOAT64 realVal = 0;
    FLOAT64 val = pelement->source_var.var_value.n;
        if (time >= 18) {
            int ival;
            std::ifstream file("data.txt");
            file >> ival;
            val = ival;
            realVal = val;
            file.close();
            time = 0;
        }
        else {
            time++;
            val = realVal;
        }

    return val;
}

MAKE_NEEDLE
(
    fuel_needle,
    BMP_FUEL_SMALL_NEEDLE,
    NULL,
    NULL,
    IMAGE_USE_TRANSPARENCY|IMAGE_USE_ERASE|IMAGE_BILINEAR_COLOR,
    0,
    150, 150,
    6, 12,
    TOTAL_FUEL_QUANTITY_GALLONS,fuel_needle_cb,
    fuel_nonlinearity,
    0
)


PELEMENT_HEADER        fuel_needle_list[] =
{
    (PELEMENT_HEADER)&fuel_needle,
    NULL
};


/////////////////////////////////////////////////////////////////////////////
MAKE_STATIC
(
    fuel_background,
    BMP_FUEL_SMALL_BACKGROUND,
    &fuel_needle_list,
    NULL,
    IMAGE_USE_TRANSPARENCY,
    0,
    9, 0
)

PELEMENT_HEADER        fuel_list    = &fuel_background.header;

/////////////////////////////////////////////////////////////////////////////
MOUSE_BEGIN( fuel_mouse_rect, HELPID_GAUGE_FUEL, 0, 0 )
MOUSE_END


/////////////////////////////////////////////////////////////////////////////
#undef GAUGE_NAME
#undef GAUGEHDR_VAR_NAME
#undef GAUGE_W

Any help is appreciated!

 

[DragonflightDesign]

Have you tried stepping though with a debugger to see what is actually being returned? I still use fopen(), fclose(), etc. rather than C++ streams so I can't help with 'is the code okay?'.

 

[Bitman]

Have you tried stepping though with a debugger to see what is actually being returned? I still use fopen(), fclose(), etc. rather than C++ streams so I can't help with 'is the code okay?'.

I'll do this tomorrow and let you know how it goes. Your guide is godly by the way. I have learned so much more with that than with just the documentation.

 

[Bitman]

Have you tried stepping though with a debugger to see what is actually being returned? I still use fopen(), fclose(), etc. rather than C++ streams so I can't help with 'is the code okay?'.

I figured out that I just had the file I was reading from in the wrong location. I had it in the gauges folder instead of the main FSX folder with the exe where it should be.

 

[DragonflightDesign]

Yeah, that's caught a few people out. One of the first things that any aircraft of mine does is to load a set of paths to various sim folders so I can read/write anything/anywhere as needed.