Calling the host

Call host functions by numeric id (typed, with zero encoding or decoding).

For the full list see "UI development". Each call below comes with a one-line usage note and an example; signatures come from Lib/c/vml_ui.h (the authoritative source).

callwithdouble4(double* v)

The same calling convention, with 3 double arguments (passed in D1..D3); the return value overwrites D0.

double v[4];
v[0] = VML_CALL_ECHO_DOUBLE;
v[1] = 1.0; v[2] = 2.0;
double r = callwithdouble4(v);

callwithfloat8(float* v)

The same, with 7 float arguments (passed in F1..F7); the return value overwrites F0. Note: the call number also lives in F0 (v[0]), so it must be exactly representable as a float - small integers are always safe.

float v[8];
v[0] = VML_CALL_ECHO_FLOAT;
v[1] = 1.0; v[2] = 2.0;
float r = callwithfloat8(v);

callwithint8(int* v)

Calls a host function by numeric id: v[0] is the call number (see the VML_CALL_* macros) and v[1..7] are the arguments. The return value **overwrites v[0]** - so after the call you can no longer read the v[0] you passed in. That is by design, not a bug. It is much faster than ui_call_json (the arguments go straight into registers, one call with zero encoding or decoding); the price is that the types are fixed in the signature. An unregistered id or mismatched types never crash - they write back a negative error code (-2 arguments, -6 no such call number, -9 internal host error).

int v[8];
v[0] = VML_CALL_ECHO_INT;
v[1] = 1; v[2] = 2; v[3] = 3;
int r = callwithint8(v);   /* 1 + 2x10 + 3x100 = 321 */

callwithlong4(long* v)

The same, with 3 long arguments (passed in L1..L3); the return value overwrites L0. Only the long-integer registers can hold a 64-bit value - the general-purpose registers are 32-bit.

long v[4];
v[0] = VML_CALL_ECHO_LONG;
v[1] = 1; v[2] = 2;
long r = callwithlong4(v);