====== (This is the legacy documentation for stable SDL2, the current stable version; [https://wiki.libsdl.org/SDL3/ SDL3] is the current development version.) ======
= SDL_MouseWheelEvent =

Mouse wheel event structure (event.wheel.*)

== Header File ==

Defined in [SDL_events.h](https://github.com/libsdl-org/SDL/blob/SDL2/include/SDL_events.h), but apps should _only_ `#include "SDL.h"`!

== Syntax ==

<syntaxhighlight lang='c'>
typedef struct SDL_MouseWheelEvent
{
    Uint32 type;        /**< ::SDL_MOUSEWHEEL */
    Uint32 timestamp;   /**< In milliseconds, populated using SDL_GetTicks() */
    Uint32 windowID;    /**< The window with mouse focus, if any */
    Uint32 which;       /**< The mouse instance id, or SDL_TOUCH_MOUSEID */
    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 toward the user */
    Uint32 direction;   /**< Set to one of the SDL_MOUSEWHEEL_* defines. When FLIPPED the values in X and Y will be opposite. Multiply by -1 to change them back */
    float preciseX;     /**< The amount scrolled horizontally, positive to the right and negative to the left, with float precision (added in 2.0.18) */
    float preciseY;     /**< The amount scrolled vertically, positive away from the user and negative toward the user, with float precision (added in 2.0.18) */
    Sint32 mouseX;      /**< X coordinate, relative to window (added in 2.26.0) */
    Sint32 mouseY;      /**< Y coordinate, relative to window (added in 2.26.0) */
} SDL_MouseWheelEvent;</syntaxhighlight>

== Code Examples ==

<syntaxhighlight lang='c++'>

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 ...
}
</syntaxhighlight>

== 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|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|Remarks]] for details (>= SDL 2.0.4)
|-
|float
|'''preciseX'''
|the amount scrolled horizontally, positive to the right and negative to the left, with float precision (added in 2.0.18)
|-
|float
|'''preciseY'''
|the amount scrolled vertically, positive away from the user and negative toward the user, with float precision (added in 2.0.18)
|}

== Related Enumerations ==

:[[SDL_EventType]]

== Related Structures ==

:[[SDL_Event]]
:[[SDL_MouseButtonEvent]]
:[[SDL_MouseMotionEvent]]

----
[[CategoryAPI]], [[CategoryAPIStruct]], [[CategoryStruct]], [[CategoryEvents]]