sdl_seteventfilter(3) [redhat man page]
SDL_SetEventFilter(3) SDL API Reference SDL_SetEventFilter(3) NAME
SDL_SetEventFilter- Sets up a filter to process all events before they are posted to the event queue. SYNOPSIS
#include "SDL.h" void SDL_SetEventFilter(SDL_EventFilter filter); DESCRIPTION
This function sets up a filter to process all events before they are posted to the event queue. This is a very powerful and flexible fea- ture. The filter is prototyped as: typedef int (*SDL_EventFilter)(const SDL_Event *event); If the filter returns 1, then the event will be added to the internal queue. If it returns 0, then the event will be dropped from the queue. This allows selective filtering of dynamically. There is one caveat when dealing with the SDL_QUITEVENT event type. The event filter is only called when the window manager desires to close the application window. If the event filter returns 1, then the window will be closed, otherwise the window will remain open if pos- sible. If the quit event is generated by an interrupt signal, it will bypass the internal queue and be delivered to the application at the next event poll. Note: Events pushed onto the queue with SDL_PushEvent or SDL_PeepEvents do not get passed through the event filter. Note: Be Careful! The event filter function may run in a different thread so be careful what you do within it. SEE ALSO
SDL_Event, SDL_GetEventFilter, SDL_PushEvent SDL
Tue 11 Sep 2001, 22:59 SDL_SetEventFilter(3)
Check Out this Related Man Page
SDL_Event(3) SDL API Reference SDL_Event(3) NAME
SDL_Event- General event structure STRUCTURE DEFINITION
typedef union{ Uint8 type; SDL_ActiveEvent active; SDL_KeyboardEvent key; SDL_MouseMotionEvent motion; SDL_MouseButtonEvent button; SDL_JoyAxisEvent jaxis; SDL_JoyBallEvent jball; SDL_JoyHatEvent jhat; SDL_JoyButtonEvent jbutton; SDL_ResizeEvent resize; SDL_ExposeEvent expose; SDL_QuitEvent quit; SDL_UserEvent user; SDL_SywWMEvent syswm; } SDL_Event; STRUCTURE DATA
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 expose Application window expose event quit Application quit request event user User defined event syswm Undefined window manager event DESCRIPTION
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 SDL_ACTIVEEVENT SDL_ActiveEvent SDL_KEYDOWN/UP SDL_KeyboardEvent SDL_MOUSEMOTION SDL_MouseMotionEvent SDL_MOUSEBUTTONDOWN/UP SDL_MouseButtonEvent SDL_JOYAXISMOTION SDL_JoyAxisEvent SDL_JOYBALLMOTION SDL_JoyBallEvent SDL_JOYHATMOTION SDL_JoyHatEvent SDL_JOYBUTTONDOWN/UP SDL_JoyButtonEvent SDL_QUIT SDL_QuitEvent SDL_SYSWMEVENT SDL_SysWMEvent SDL_VIDEORESIZE SDL_ResizeEvent SDL_VIDEOEXPOSE SDL_ExposeEvent SDL_USEREVENT SDL_UserEvent USE
The SDL_Event structure has two uses o Reading events on the event queue o Placing events on the event queue Reading events from the event queue is done with either SDL_PollEvent or SDL_PeepEvents. We'll use SDL_PollEvent and step through an exam- ple. 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(&test_event)) { 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. switch(test_event.type) { We need to know what kind of events we're looking for and the event type's of those events. So lets assume we want to detect where the user is moving the mouse pointer within our application. We look through our event types and notice that SDL_MOUSEMOTION is, more than likely, the event we're looking for. A little more research tells use that SDL_MOUSEMOTION events are handled within the SDL_MouseMotion- Event structure which is the motion member of SDL_Event. We can check for the SDL_MOUSEMOTION event type within our switch statement like so: case SDL_MOUSEMOTION: All we need do now is read the information out of the motion member of test_event. printf("We got a motion event. "); printf("Current mouse position is: (%d, %d) ", test_event.motion.x, test_event.motion.y); break; default: printf("Unhandled Event! "); break; } } printf("Event queue empty. "); 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_Peep- Events 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. SDL_Event user_event; user_event.type=SDL_USEREVENT; user_event.user.code=2; user_event.user.data1=NULL; user_event.user.data2=NULL; SDL_PushEvent(&user_event); SEE ALSO
SDL_PollEvent, SDL_PushEvent, SDL_PeepEvents SDL
Tue 11 Sep 2001, 22:59 SDL_Event(3)