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kas1e
getting screen from rastport ?
Posted on: 2017/1/15 8:00    #1
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Is it possible to get screen from rastport ? I mean something like:

struct RastPort *rp;

rp = blbalbalb;

GetScreenDrawInfo(rp->Layer->Window->WScreen);

Last one didn't works, just as example.


Edited by kas1e on 2017/1/15 8:21:06
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salass00
Re: getting screen from rastport ?
Posted on: 2017/1/15 10:02    #2
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@kas1e

Where does the rastport come from?

If it's not a layered (window) rastport then rp->Layer will be NULL so rp->Layer->Window->WScreen won't work.

If you know it's the screen rastport (the one embedded in the Screen structure) there is some pointer arithmetic you could do to get back the screen pointer, but if you know this then you might as well pass the screen pointer directly to your function instead of just the rastport.
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jabirulo
Re: getting screen from rastport ?
Posted on: 2017/1/15 10:06    #3
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And something like:

struct RastPort *rp = blbalbalb;
struct Layer *layer = rp->Layer;
struct Screen *scr = ((struct Window *)(layer->Window))->WScreen;

But as salas00 pointed out it could be that 'layer->Window == NULL'.
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kas1e
Re: getting screen from rastport ?
Posted on: 2017/1/15 12:21    #4
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@all
Quote:

If you know it's the screen rastport (the one embedded in the Screen structure) there is some pointer arithmetic you could do to get back the screen pointer, but if you know this then you might as well pass the screen pointer directly to your function instead of just the rastport.


Yep, its the screen rastpot. It was situation when i have function (in one of many source files) which have only rastport as parametr, and no window/screen. And i was in hope somehow got screen from rastport without needs to rewrite function to get also screen parametr (and without needs to rewrite all parts in whole programm where happens call to that function).
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salass00
Re: getting screen from rastport ?
Posted on: 2017/1/15 20:26    #5
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@kas1e

In that case using container_of macro:

#ifdef __GNUC__
#define container_of(ptr, type, member) ({ \
    const typeof( ((type *)0)->member ) *__mptr = (ptr); \
    (type *)( (char *)__mptr - offsetof(type, member) );})
#else
#define container_of(ptr, type, member) ( (type *)( (char *)(ptr) - offsetof(type, member) ) )
#endif


You can do:

struct RastPort *rp;
struct Screen *screen;

screen = container_of(rp, struct Screen, RastPort);

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