type The type of event
active Activation event
key Keyboard event
motion Mouse motion event
button Mouse button event
jaxis Joystick axis motion event
jball Joystick trackball motion event
jhat Joystick hat motion event
jbutton Joystick button event
resize Application window resize event
quit Application quit request event
user User defined event
The SDL_Event union is the core to all event handling is SDL, its probably the most important structure after SDL_Surface. SDL_Event is a union of all event structures used in SDL, using it is a simple matter of knowing which union member relates to which event type.
Event type Event Structure
The SDL_Event structure has two uses
Reading events on the event queue
Placing events on the event queue
First off, we create an empty SDL_Event structure.
SDL_Event test_event; SDL_!PollEvent? removes the next event from the event queue, if there are no events on the queue it returns 0 otherwise it returns 1. We use a while loop to process each event in turn.
while(SDL_!PollEvent?( The SDL_!PollEvent? function take a pointer to an SDL_Event structure that is to be filled with event information. We know that if SDL_!PollEvent? removes an event from the queue then the event information will be placed in our test_event structure, but we also know that the type of event will be placed in the type member of test_event. So to handle each event type seperately we use a switch statement.
All we need do now is read the information out of the motion member of test_event.
It is also possible to push events onto the event queue and so use it as a two-way communication path. Both SDL_!PushEvent? and SDL_!PeepEvents? allow you to place events onto the event queue. This is usually used to place a SDL_USEREVENT on the event queue, however you could use it to post fake input events if you wished. Creating your own events is a simple matter of choosing the event type you want, setting the type member and filling the appropriate member structure with information.