On 11/21/2014 5:57 AM, Paul wrote:
This is a tad off topic now but I'm struggling to get a window on screen
as SDL_CreateWindow is failing, here's what I've got:
try{
DerelictSDL2.load();
}catch(Exception e){
writeln("Failed to load DerelictSDL2 :( %s", e.msg);
return;
}
Before getting to your issue, I'd like to point out that this is a
needless redundancy. You are adding anything by catching an exception
here and printing to the console that the library didn't load. The
exception message will tell you that already. I suggest you just remove
the try..catch and let the exception propagate. The only reason to catch
a DerelictException here is if you want to do something other than print
the message to the console, like display a message box or write to a log
file.
try{
SDL_Init(SDL_INIT_EVERYTHING);
}catch(Exception e){
writeln("Can't init SDL :( %s", e.msg);
return;
}
SDL_Init isn't goint to throw an exception. It can't. It's a function in
a C library and C doesn't know anything about D exceptions. If you look
at the documentation for SDL_Init[1], you will find that it returns a
negative number on failure and 0 on success.
if( SDL_Init( SDL_INIT_EVERYTHING ) < 0 ) {
// See below for how to handle this
}
SDL_Window *testWindow;
//temporary magic numbers ahoy
testWindow = SDL_CreateWindow( "Test Window", SDL_WINDOWPOS_UNDEFINED,
SDL_WINDOWPOS_UNDEFINED, 800, 600, SDL_WINDOW_RESIZABLE );
if( testWindow == null ) {
writeln("Window could not be created!");
return;
} else {
SDL_Surface* testSurface;
testSurface = SDL_GetWindowSurface(testWindow);
}
Everything seems to initialise ok but SDL_CreateWindow always returns
null. For some reason I can't use DerelictException which I guess might
help me dig deeper. AFAIK there are no issues with this machine's
hardware - I can certainly run other SDL-based apps on it.
Again, DerelictExceptions aren't going to help you here. They are only
thrown when the load function fails (to manipulate a DerelictException
directly, import derelict.util.exception.) To get an error message out
of SDL, you need to call SDL_GetError, which returns a const( char )*.
void printSDLError( string msg ) {
import std.conv : to;
import std.stdio : writefln;
writefln("%s: %s", msg, to!string( SDL_GetError() ));
}
...
if( testWindow == null )
{
printSDLError( "Failed to create window." );
return;
}
I prefer to wrap it up in a subclass of Error. Others may prefer
Exception, but when I throw an SDLError I don't intend to catch it. I
really want the app to exit.
class SDLError : Error
{
public static string errStr() @property
{
import std.conv : to;
import derelict.sdl2.sdl : SDL_GetError;
return to!string( SDL_GetError() );
}
public this( string msg, string file = __FILE__, size_t line =
__LINE__ )
{
import std.string : format;
auto fmsg = format( "%s: %s", msg, errStr );
super( fmsg, file, line );
}
}
Now it becomes:
DerelictSDL2.load();
if( SDL_Init( SDL_INIT_EVERYTHING ) < 0 )
{
throw new SDLError( "Failed to initialize SDL" );
}
testWindow = SDL_CreateWindow( ... );
if( !testWindow )
{
throw new SDLError( "Failed to create window" );
}
Whichever approach you choose, SDL_GetError will shed light on why any
SDL call failed as long as you call it immediately upon failure.
[1]
https://wiki.libsdl.org/SDL_Init?highlight=%28%5CbCategoryInit%5Cb%29%7C%28CategoryEnum%29%7C%28CategoryStruct%29
