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SDL Wiki

SDL_MouseWheelEvent

A structure that contains mouse wheel event information.

Data Fields

Uint32

type

SDL_MOUSEWHEEL

Uint32

timestamp

timestamp of the event

Uint32

windowID

the window with mouse focus, if any

Uint32

which

the mouse instance id, or SDL_TOUCH_MOUSEID; see Remarks for details

Sint32

x

the amount scrolled horizontally, positive to the right and negative to the left

Sint32

y

the amount scrolled vertically, positive away from the user and negative towards the user

Uint32

direction

SDL_MOUSEWHEEL_NORMAL or SDL_MOUSEWHEEL_FLIPPED; see Remarks for details (>= SDL 2.0.4)

Code Examples


SDL_Event event;
while( SDL_PollEvent( &event ) )
{
    if(event.type == SDL_MOUSEWHEEL)
    {
        if(event.wheel.y > 0) // scroll up
        {
             // Put code for handling "scroll up" here!
        }
        else if(event.wheel.y < 0) // scroll down
        {
             // Put code for handling "scroll down" here!
        }

        if(event.wheel.x > 0) // scroll right
        {
             // ...
        }
        else if(event.wheel.x < 0) // scroll left
        {
             // ...
        }
    }
    else if(event.type == SDL_MOUSEBUTTONDOWN)
    {
        // ... handle mouse clicks ...
    }

    // ... handle other kinds of events ...
}

Remarks

SDL_MouseWheelEvent is a member of the SDL_Event union and is used when an event of type SDL_MOUSEWHEEL is reported. You would access it through the event's wheel field.

An SDL_MOUSEWHEEL event occurs whenever a user moves the mouse wheel.

Movements to the left generate negative x values and to the right generate positive x values. Movements down (scroll backward) generate negative y values and up (scroll forward) generate positive y values.

which may be SDL_TOUCH_MOUSEID, for events that were generated by a touch input device, and not a real mouse. You might want to ignore such events, if your application already handles SDL_TouchFingerEvent.

SDL does not abstract the mouse wheel scroll directions to be consistent across all platforms (SDL_MOUSEWHEEL_NORMAL). If direction is SDL_MOUSEWHEEL_FLIPPED the values in x and y will be opposite. Multiply by -1 to change them back.

SDL_EventType
SDL_Event
SDL_MouseButtonEvent
SDL_MouseMotionEvent

CategoryStruct, CategoryEvents


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