if (SDL_PollEvent(&event))
if( event.type == SDL_KEYDOWN )
if( event.key.keysym.sym == SDLK_c )
{
int cursorMode = 1;
Cursor cursor;
cursor.initCursor();
while (cursorMode == 1)
{
if (SDL_PollEvent(&event))
if( event.type == SDL_KEYDOWN )
if( event.key.keysym.sym == SDLK_c )
cursorMode = 0; //setting to 0 exits cursor mode
// do cursor stuff here
}
cursor.~Cursor();
}
[SDL] Keyboard Input Question [Almost Solved, Maybe Not Optimally]
Author
So I tried searching for the answer on here and on google to no avail. If someone could set me in the right direction, I'd be most appreciative.
EDIT: I am using C++ language and the SDL library. For the time being I am using DEVC++ IDE, but am switching to the Microsoft C++ very soon.
Objective: in my keyboard handling routine I would like to have the key press 'c' go into "Cursor Mode". Upon pressing 'c' a second time the program user exits "Cursor Mode". "Cursor Mode" is simply a game state where an 'X' is placed on the screen that can be incrementally moved across the game space for purposes of interaction.
Code Snippet:
Discussion of Problem:
When the program is running I can press 'c' to get into cursor mode; however, when pressed a second time, I cannot exit out of cursor mode. If I change the second statement from the code [if( event.key.keysym.sym == SDLK_c )] to [if( event.key.keysym.sym == SDLK_d )], the 'd' key press will exit from cursor mode! wtf?
I know this is probably a basic problem, but I am a beginner and cannot solve it yet. Please help!
I will continue to work on the problem in the mean time. Thanks in advance!
[Edited by - signal_ on March 16, 2008 1:22:26 PM]
I can't answer your question exactly, but I can guarantee you can avoid a lot of headaches later by separating your logic code from your input code by writing a small wrapper. Doing that will not only solve this problem, but many other potential issues down the road, and make your code a hell of a lot cleaner.
Author
Ok. So I solved it. However I am unsure as to whether this solution is optimal. Also, thanks fd9_ for the advice; it is noted and I always appreciate the insight.
I added a check for the cursorMode flag before I enter "Cursor Mode". This seems to solve it.
My theory on what is/was happening: one single keystroke of 'c' satisfied both if statements (the outer and the nested one). This led to the poor outcome of being inexorably stuck in the nested loop. I am still shaky on the understanding, but I should probably "get it" eventually. Also, a proper explanation from any of you smart coders will be appreciated as well.
Best wishes.
UPDATED Code Snippet:
EDIT: So I tried some more things and I think I have fully solved the problem. I found an example online. This example said that a common mistake is to handle only the KEYDOWN event and not handling the KEYUP event. Using this knowledge I was able to formulate a suitable solution; maybe not the most optimal, but it works for me.
[Edited by - signal_ on March 16, 2008 5:21:13 PM]
I added a check for the cursorMode flag before I enter "Cursor Mode". This seems to solve it.
My theory on what is/was happening: one single keystroke of 'c' satisfied both if statements (the outer and the nested one). This led to the poor outcome of being inexorably stuck in the nested loop. I am still shaky on the understanding, but I should probably "get it" eventually. Also, a proper explanation from any of you smart coders will be appreciated as well.
Best wishes.
UPDATED Code Snippet:
//initialize cursorMode flagint cursorMode = 1;if (SDL_PollEvent(&event)) if( event.type == SDL_KEYDOWN ) if( event.key.keysym.sym == SDLK_c && cursorMode == 1) // NOTE CHANGE {// the above if statement checks the cursorMode flag!!! Cursor cursor; cursor.initCursor(); while (cursorMode == 1) { if (SDL_PollEvent(&event)) if( event.type == SDL_KEYDOWN ) if( event.key.keysym.sym == SDLK_c ) cursorMode = 0; //setting to 0 exits cursor mode // do cursor stuff here } cursor.~Cursor(); }EDIT: So I tried some more things and I think I have fully solved the problem. I found an example online. This example said that a common mistake is to handle only the KEYDOWN event and not handling the KEYUP event. Using this knowledge I was able to formulate a suitable solution; maybe not the most optimal, but it works for me.
[Edited by - signal_ on March 16, 2008 5:21:13 PM]
You seem to be calling SDL_PollEvent() twice in one loop. Each time you call SDL_PollEvent, it retrieves a different event, so you usually don't want it called twice anywhere in your code.
What you'd want might be simular to this:
What you'd want might be simular to this:
Cursor cursor;while( SDL_PollEvent(&event) ) if( event.type == SDL_KEYDOWN ) { if( event.key.keysym.sym == SDLK_c) { if(cursor.cursorModeIsOn() == true) cursor.turnCursorModeOff() else //if(cursor.cursorModeIsOn() == false) cursor.turnCursorModeOn() } }//Do cursor stuff outside of your event poll.This topic is closed to new replies.
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