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c4c0d3m0n

invalid conversion from const SDL_Rect*' to SDL_Rect*'

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SDL_Surface* Font::renderText( std::string text ) const
{
    int width = this->getWidth( text );

    SDL_Surface* surface = SDL_CreateRGBSurface( SDL_SRCCOLORKEY,
                                                 width, chars[0].h,
                                                 bitmap->format->BitsPerPixel,
                                                 bitmap->format->Rmask,
                                                 bitmap->format->Gmask,
                                                 bitmap->format->Bmask,
                                                 0 );


    int current_char = 0;
    SDL_Rect rect;
    rect.x = 0;
    rect.y = 0;
    while( current_char < text.length() ) {
        SDL_BlitSurface( bitmap, &chars[text[current_char]], surface, &rect );
        rect.x += chars[text[current_char]].w;
        current_char++;
    }


    return surface;
}

Compiling: font.cpp
E:\Programming\Base-Devel-Physics\font.cpp: In member function `SDL_Surface* Font::renderText(std::string) const':
E:\Programming\Base-Devel-Physics\font.cpp:93: error: invalid conversion from `const SDL_Rect*' to `SDL_Rect*'
E:\Programming\Base-Devel-Physics\font.cpp:93: error:   initializing argument 2 of `int SDL_UpperBlit(SDL_Surface*, SDL_Rect*, SDL_Surface*, SDL_Rect*)'
.. Ugh I need Font::renderText() to be const, because I'm passing constant references of Font objects in certain functions that use this function. Theoretically, a renderText() function that renders to a extranous surface and returns that should be totaly okay with being const. I don't quite understand what I'm doing wrong.

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Well, your function is (I assume, given the differing function names) attempting to modify chars[text[current_char]], which is (I assume, again, given the lack of context) a constant member variable.

Of course, I also suspect that the argument to SDL_BlitSurface is not const mostly because the SDL C++ interface sucks, and it would indeed be a const had they thought for a second about it. Therefore, it should be safe to:

SDL_BlitSurface( bitmap,
const_cast<SDL_Rect*>(&chars[text[current_char]]),
surface,
&rect );


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Ah, that was exactly what fixed my problem. Sorry for not posting more information about my Font class, I'll try and post as much information as possible from now on.

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The destination rectangle is modified by SDL to reflect the final, clipped image. Therefore const_cast is a bad idea. Simply make a copy:

SDL_Rect copy = chars[text[current_char]];
SDL_BlitSurface( bitmap, &copy, surface, &rect );

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Quote:
Original post by rip-off
The destination rectangle is modified by SDL to reflect the final, clipped image. Therefore const_cast is a bad idea. Simply make a copy:
*** Source Snippet Removed ***


Yes, the destination rectangle is modified, but the source rectangle, which was the const offending variable, is not modified, so a const_cast is just fine.

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