parsec-vdd/docs/VDD_LIBRARY_USAGE.md

C/C++ API Usage

This document describes the legacy single-header C/C++ API at core/parsec-vdd.h. It's intentionally minimal — just enough to add/remove monitors and keep them alive. For project context, see the README. For supported display modes, see PARSEC_VDD_SPECS.md.

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Overview

Parsec VDD enables creation and management of virtual displays on Windows 10+ systems. The C/C++ API allows direct control over the driver, including querying status, adding/removing displays, and updating device state.

• Up to 16 virtual displays per adapter (the legacy header caps at 8 to avoid plugging lag — adjust if needed).
• Supports high resolutions and refresh rates (see the specs).
• Can be used independently of the Parsec app.

Check out the README to install the driver.

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API Reference

With C++ include, you should add using namespace parsec_vdd.

Device Status

enum DeviceStatus {
    DEVICE_OK = 0,             // Ready to use
    DEVICE_INACCESSIBLE,       // Inaccessible
    DEVICE_UNKNOWN,            // Unknown status
    DEVICE_UNKNOWN_PROBLEM,    // Unknown problem
    DEVICE_DISABLED,           // Device is disabled
    DEVICE_DRIVER_ERROR,       // Device encountered error
    DEVICE_RESTART_REQUIRED,   // Must restart PC to use (could ignore but would have issue)
    DEVICE_DISABLED_SERVICE,   // Service is disabled
    DEVICE_NOT_INSTALLED       // Driver is not installed
};

Query Device Status

DeviceStatus QueryDeviceStatus(const GUID *classGuid, const char *deviceId);

• Checks the status of a device by class GUID and hardware ID.
• Returns a DeviceStatus value.

Device Handle Management

Open Device Handle

HANDLE OpenDeviceHandle(const GUID *interfaceGuid);

• Opens a handle to the device interface.
• Returns INVALID_HANDLE_VALUE or a valid handle.

Close Device Handle

void CloseDeviceHandle(HANDLE handle);

• Closes a previously opened device handle.

VDD Core Operations

Constants

Constant	Value	Description
VDD_DISPLAY_ID	"PSCCDD0"	Display device ID
VDD_DISPLAY_NAME	"ParsecVDA"	Display name
VDD_ADAPTER_GUID	{00b41627-04c4-429e-a26e-0265cf50c8fa}	Adapter GUID
VDD_CLASS_GUID	{4d36e968-e325-11ce-bfc1-08002be10318}	Device class GUID
VDD_HARDWARE_ID	"Root\\Parsec\\VDA"	Hardware ID
VDD_MAX_DISPLAYS	8	Maximum virtual displays

IOCTL Codes

enum VddCtlCode {
    VDD_IOCTL_ADD     = 0x0022e004,
    VDD_IOCTL_REMOVE  = 0x0022a008,
    VDD_IOCTL_UPDATE  = 0x0022a00c,
    VDD_IOCTL_VERSION = 0x0022e010,
    VDD_IOCTL_UNKONWN = 0x0022a00c,
};

Generic DeviceIoControl

DWORD VddIoControl(HANDLE vdd, VddCtlCode code, const void *data, size_t size);

• Sends an IOCTL to the VDD device.

Query Driver Version

int VddVersion(HANDLE vdd);

• Returns the minor version of the VDD driver.

Update/Ping VDD

void VddUpdate(HANDLE vdd);

• Must be called every ~100 ms (no longer than ~200 ms apart) to keep displays alive. If pings stop for ~1 second the driver removes all virtual monitors — this is its built-in watchdog for crashed hosts. Either run a dedicated thread or schedule a timer.

Add Virtual Display

int VddAddDisplay(HANDLE vdd);

• Adds a new virtual display.
• Returns the index of the added display.

Remove Virtual Display

void VddRemoveDisplay(HANDLE vdd, int index);

• Removes the display at the given index.

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Example Usage

• Minimal demo using the legacy single-header API: core/vdd-demo.cc.

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Display Modes & Specs

See PARSEC_VDD_SPECS.md for supported resolutions and refresh rates.

Further Reading

• README.md: project overview, app features, lifecycle diagram.
• PARSEC_VDD_SPECS.md: supported display modes and technical specs.
• PARSEC_VDD_RE.md: full reverse-engineered IOCTL reference — struct layouts, lifecycle, status codes.

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