IGameInput::GetPreviousReading

Artigo
11/09/2023

Retrieves the previous IGameInputReading based on a reference reading from an optionally filtered input stream.

Syntax

HRESULT GetPreviousReading(  
         IGameInputReading* referenceReading,  
         GameInputKind inputKind,  
         IGameInputDevice* device,  
         IGameInputReading** reading  
)

Parameters

referenceReading _In_
Type: IGameInputReading*

The returned IGameInputReading interface is read sequentially before this reference reading.

inputKind _In_
Type: GameInputKind

Filter for the types of input to pull the previous reading from. The GameInputKind interface is a flag variable. You may combine multiple values to filter on multiple constants. When multiple input kinds are specified, any readings that contain at least one of the input kinds will be matched and returned.

device _In_opt_
Type: IGameInputDevice*

Filter for the specific devices to pull the previous reading from.

reading _COM_Outptr_
Type: IGameInputReading**

The returned IGameInputReading interface that comes sequentially before the referenceReading input.

Return value

Type: HRESULT

Function result. If a null IGameInputDevice pointer is passed in, it will return E_NOTIMPL.

Remarks

The GetNextReading and GetPreviousReading methods let apps walk through the input history reading by reading.

Returns a NULL value and failure HRESULT if there is no reading after the referenceReading, or if a device filter is provided for a disconnected device, or if too much time has elapsed and reference reading and returned reading have left the input-stream history buffer. The elapsed time error is rare for apps that continuously process input as the input stream maintains a half second of readings from each device in its history buffer.

The following code example demonstrates how to poll for all gamepad states from a specific device.

Microsoft::WRL::ComPtr<IGameInput> gameInput; 
Microsoft::WRL::ComPtr<IGameInputDevice> gamepad; 
Microsoft::WRL::ComPtr<IGameInputReading> prevReading; 
 
void PollGamepadInput() noexcept 
{ 
    if (!prevReading) 
    { 
        if (SUCCEEDED(gameInput->GetCurrentReading( 
            GameInputKindGamepad, 
            nullptr, 
            &prevReading))) 
        { 
            prevReading->GetDevice(&gamepad);
 
            // Application-specific code to process the initial reading 
        } 
    } 
 
    else 
    { 
        Microsoft::WRL::ComPtr<IGameInputReading> nextReading; 
        HRESULT hr = gameInput->GetNextReading( 
            prevReading.Get(), 
            GameInputKindGamepad, 
            gamepad.Get(), 
            &nextReading); 
 
        if (SUCCEEDED(hr)) 
        { 
            // Application-specific code to process the next reading 
 
            prevReading = nextReading; 
        } 
 
        else if (hr != GAMEINPUT_E_READING_NOT_FOUND) 
        { 
            gamepad = nullptr; 
            prevReading = nullptr; 
        } 
    } 
}

Requirements

Header: GameInput.h

Library: xgameruntime.lib

Supported platforms: Windows, Xbox One family consoles and Xbox Series consoles

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