OpenEuphoria

SDL, keyboard and event handling

• Posted by ChrisB (moderator) Nov 01, 2022
• 1029 views

Hi

Using Andy's SDL2 lib

Pointers drive me insane!

to check the keyboard to see if ESC is pressed

atom key = 0 
integer scanning = 1, scancode 
 
while scanning = 1 do 
	SDL_PumpEvents() 
	key = SDL_GetKeyboardState(key) 
	 
	if peek(key+SDL_SCANCODE_ESCAPE) > 0 then 
		scanning = 0 
	end if 
end while 
 
return scancode 
 

to check the keyboard for any key pressed

atom key = 0, ev_type = 0 
integer scanning = 1, scancode 
 
while scanning = 1 do 
	 
	SDL_PumpEvents() 
	 
	key = SDL_GetKeyboardState(key) 
	 
	--if peek(key+SDL_SCANCODE_ESCAPE) > 0 then 
	--	scanning = 0 
	--end if 
 
    for i = 4 to 99 do 
        if peek(key + i) > 0 then 
            scanning = 0   
            scancode = i 
        end if 
    end for 
 
end while 
 
return scancode 
 

These work, and do the job.

But, to check the keyboard for an event, like keydown, or indeed other event types

atom ev = 0, ev_type = 0 
 
printf(1, "M_wait_key\n", {}) 
 
while SDL_WaitEvent(ev) do 
        if ev > 0 then 
            ev_type = peek(ev) 
            printf(1, "%d, %d\n", {ev, ev_type}) 
            if wait_key() then end if 
            if ev_type = SDL_KEYDOWN then return 1 end if 
         end if 
end while     
 
return 0 
 
while 1 do 
    if SDL_PollEvent(ev) then 
        if ev > 0 then 
            ev_type = peek(ev) 
            printf(1, "%d, %d\n", {ev, ev_type}) 
            if ev_type = SDL_KEYDOWN then return 1 end if 
         end if 
    end if 
end while 
 
return 0 
 

Neither of these work

My thinking went like this

--Uses pointers and members addressing 
--SDL_PollEvent to get the next event from the event queue  
--to put in a test_event structure, 
--the first member of which will be the event type  
--all events have different structures (with members specific to the structure) 
--but for this function only need the first member. 
--see SDL_KEYBOARD event 
--Uint32 type the event type; SDL_KEYDOWN or SDL_KEYUP 
 

Any pointers (sorry) in the right direction would be greatly appreciated.

Cheers Chris

Update : just remembering this has kind of already been addressed, but reading the docs, pollevent places the next event structure from the event queue into an event structure (which doesn't look like a union), so we should be able to get the event type, the first member, from that structure.

Cheers

Chris