Discussion:
how to check for an event
(too old to reply)
speartip
2017-02-13 16:15:07 UTC
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Hi, wanted to know how to code for an error state in the following code. I am new to SDL. I simply want a true to some value if a window was successfully created. I've made this window generation a subroutine:


Code:

#include <SDL.h>
#include "make_Window.h"

void make_Window(int horizontal, int vertical) //SDL_Window *window)
{

SDL_Init(SDL_INIT_EVERYTHING);

// Create a Window in the middle of the screen
SDL_Window *window = 0;
window = SDL_CreateWindow("Hello World!",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
horizontal, vertical,
SDL_WINDOW_SHOWN);
// Delay so that we can see the window appear
SDL_Delay(2000);

}
Brian Puthuff
2017-02-13 16:24:37 UTC
Permalink
https://wiki.libsdl.org/SDL_CreateWindow

SDL_CreateWindow will return NULL if failed.

Not sure if that's what you are asking.
Post by speartip
Hi, wanted to know how to code for an error state in the following code. I
am new to SDL. I simply want a true to some value if a window was
#include
#include "make_Window.h"
void make_Window(int horizontal, int vertical) //SDL_Window *window)
{
SDL_Init(SDL_INIT_EVERYTHING);
// Create a Window in the middle of the screen
SDL_Window *window = 0;
window = SDL_CreateWindow("Hello World!",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
horizontal, vertical,
SDL_WINDOW_SHOWN);
// Delay so that we can see the window appear
SDL_Delay(2000);
}
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speartip
2017-02-13 21:03:55 UTC
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Thats it. Thx!! I am just getting use to their library.
speartip
2017-02-14 03:10:14 UTC
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Well, a bit premature!


Code:

if (window == NULL) {
// In the case that the window could not be made...
printf("Could not create window: %s\n", SDL_GetError());
return 1;




I experienced problems with printf only to find out my IDE Eclipse is problematic with printf. After adding #include <cstdio> the printf was printing
the "Could not create window:" portion, but not the rest. Can anyone please tell me what is supposed to be printed after it : %s\n",SDL_GetError()
and how to get printf functional?

Thank you.
speartip
2017-02-14 03:12:11 UTC
Permalink
logically its working; in the braces within the printf is not functioning correctly.
speartip
2017-02-15 18:02:11 UTC
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I wanted to update, to focus the problem at hand and make sure nobody thought I was asking them to fix my compiler. No way!

This line initializes.

Code:


if (SDL_Init(SDL_INIT_EVERYTHING) == 0) {
printf("SDL_Init failed: %s\n", SDL_GetError());
return 1;}




Here I've purposely induced an error state by changing
Code:
(SDL_Init(SDL_INIT_EVERYTHING) != 0) to (SDL_Init(SDL_INIT_EVERYTHING) == 0)



The error is then thrown and 1/2 of the statement is printed from printf above see bold below:

SDL_Init failed: . But the other half of the statement isn't printed.

But no value for
Code:
SDL,GetError()

is returned on the same line.


In short my printf statement is cut in half.
speartip
2017-02-15 18:04:09 UTC
Permalink
printf("SDL_Init failed: %s\n", SDL_GetError())
Jonathan Dearborn
2017-02-15 18:16:21 UTC
Permalink
It doesn't sound like you've actually induced an error state, but instead
are printing regardless of whether or not there is an error.

If there is not an actual error, you might expect SDL_GetError() to return
an empty string (not sure if that is specified by the API). So you would
see:

SDL_Init failed:

Because the %s was replaced by nothing.

Jonny D
Post by speartip
printf("SDL_Init failed: %s\n", SDL_GetError())
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speartip
2017-02-15 21:04:40 UTC
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It will only print if
Code:
SDL_Init(SDL_INIT_EVERYTHING) == 0)

. But won't print error info.
Program proceeds normally if I change it to:
Code:
SDL_Init(SDL_INIT_EVERYTHING) != 0)



It won't print under just any circumstance.
speartip
2017-02-15 21:07:28 UTC
Permalink
sorry, in reply to this:

are printing regardless of whether or not there is an error.
Jonathan Dearborn
2017-02-15 21:23:05 UTC
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Yes, but do you understand my point? There is no error to print, so
SDL_GetError() will not return an error message. Since there is no error,
go ahead and keep working on the rest of the program.

Jonny D
Post by Jonathan Dearborn
are printing regardless of whether or not there is an error.
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speartip
2017-02-15 23:14:50 UTC
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There is no error to print, so SDL_GetError()

No, I got you. Thanks for your patience. I was just experimenting b/c I wanted to see some of the error codes produced, etc.
speartip
2017-02-15 23:18:38 UTC
Permalink
Oh, ad I wanted a code so I could make sure the printf function was working. Right now I just get 1/2 back:

printf("SDL_Init failed: %s\n", SDL_GetError())

That's ok, I just want to make the code does work, and without an error hard to say.

But I've beat this topic up, so I am just going to move on here ...
Jonathan Dearborn
2017-02-16 00:22:23 UTC
Permalink
Well, you could use SDL_SetError() to at least show something.

https://wiki.libsdl.org/SDL_SetError

Jonny D
Post by speartip
Oh, ad I wanted a code so I could make sure the printf function was
printf("SDL_Init failed: %s\n", SDL_GetError())
That's ok, I just want to make the code does work, and without an error hard to say.
But I've beat this topic up, so I am just going to move on here ...
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