General-Query-Functions

The following are helper functions to query information from the state message, meaning that they will only return valid information following the invocation of [hpc_InitializeApp()](./State-Functions.md#hpc_InitializeApp()), and only return new information after hpc_RefreshState().

hpc_GetStateAsJSON

size_t hpc_GetStateAsJSON(char *out_buf, size_t out_buf_sz)

Returns

The current state message, serialized into a char buffer as JSON.

Args

char *out_buf, size_t out_buf_sz

Description

Mostly useful for debugging - custom message queries can be constructed without an external JSON serializer, using the helper functions in libHoloPlayCore.h.

hpc_GetHoloPlayServiceVersion

size_t hpc_GetHoloPlayServiceVersion(char *out_buf, size_t out_buf_sz)

Returns

Current version of HoloPlay Service, as a string.

Args

char *out_buf, size_t out_buf_sz

hpc_GetNumDevices

int hpc_GetNumDevices(void)

Returns

Number of Looking Glass devices connected with valid calibrations.

Args

None

hpc_GetDeviceHDMIName

size_t hpc_GetDeviceHDMIName(int dev_index, char *out_buf, size_t out_buf_sz)

Returns

Looking Glass device name retrieved from EDID.

Args

int dev_index, char *out_buf, size_t out_buf_sz

hpc_GetDeviceSerial

size_t hpc_GetDeviceSerial(int dev_index, char *out_buf, size_t out_buf_sz)

Returns

Serial number of device (same as the one printed on label).

Args

int dev_index, char *out_buf, size_t out_buf_sz

hpc_GetDeviceType

size_t hpc_GetDeviceType(int dev_index, char *out_buf, size_t out_buf_sz)

Returns

Device type as string. Currently one of the following:

• "standard": the legacy 8.9" display

• "large": the first generation 15.6" device

• "pro": the legacy 15.6" Pro Workstation device

• "8k": the first generation 8K device

• "portrait": the Looking Glass Portrait

• "4k_gen2": the second generation 16"

• "8k_gen2": the second generation 32"

Args

int dev_index, char *out_buf, size_t out_buf_sz

*Note on String Return Functions

Any function of the form "size_t hpc_DoThing(..., char* out_buf, size_t out_buf_sz)" copies a string into a preallocated buffer of size out_buf_sz. The buffer is allocated and owned by the caller.

These functions return 0 if out_buf_sz was sufficient, or the actual size of string if out_buf_sz was too small.

This makes it much easier to pass strings into managed memory (i.e. for .NET bindings). Most of the strings returned by these functions are quite small.