Amiga Screen Resolutions, Modes & Overscan

[EDanaII]

Greetings All,

I posted this earlier, but it looks like I accidentally posted it in a News Forum. I'm guessing the moderator hasn't approved it yet. Yo, Mod? Don't bother, my bad, or if you do, by chance, approve it, remove it instead.

Anywho... for some time now, I've been playing with various Amiga C++ Frameworks with little or no success. So, just for giggles, I decided to experiment with my own. First I created a prototype meant simply to open a window and communicate with it. Next, also just for giggles, since we're talkin' Amiga here, I created a class for Displays (Screens). At present, using it looks something like this:

Code: [Select]


IntuitionBase = IntuitionLibrary.GetIntuitionBase( );

Display screen = Display(320, 200);
screen.SetLocation(0, 120);
screen.DisplayMode = DisplayModeId::LoRes;
screen.OverscanMode = OverscanModeId::Text;
screen.SetTitle("Low Res Screen.");
screen.open( );
Delay(50 * 5);

screen.close( );
IntuitionLibrary.close( );


Now, the DisplayMode and it's associated enum, DisplayModeId derive their values from the C header file, graphics/modeid.h, and what I'm wondering is this: doesn't the modeid effectively determine the resolution? If I specify LORES_KEY (from modeid.h) isn't that the same as declaring a screen resolution of 320x200? And specifying it as HIRES_KEY would be the same as declaring a 640x200 resolution, while declaring HIRESLACE_KEY is the same as 640x400?

I ask because, at present, I'm declaring a screen as "Display screen = Display(320, 200)" when it seems to me this should be the same as "Display(DisplayModeId::LoRes)".

Of course, this then begs the question, what about Overscan? How does it further affect the resolution? If the developer declares LOWRES_KEY and an overscan of OSCAN_MAX, how does this increase the display area? Does know where I might look to further define how these two modes interact?

Thoughts welcome.

[EDanaII]

Ah... you're right. It's been so long that I'd forgot about the fact that the Amiga would scroll if you defined an area too large for the screen. So, since they are independent, the current method for screen creation seems fine.

Thanks for the response.

[EDanaII]

OK, next question for any who care to answer.

I walked through the intuition_protos.h file looking for routines I need to incorporate into a C++ Screen class and I found these:

Code: [Select]

BOOL CloseScreen( struct Screen *screen );
VOID DisplayBeep( struct Screen *screen );
VOID MoveScreen( struct Screen *screen, LONG dx, LONG dy );
VOID ScreenToBack( struct Screen *screen );
VOID ScreenToFront( struct Screen *screen );
VOID ShowTitle( struct Screen *screen, LONG showIt );
LONG MakeScreen( struct Screen *screen );
? LONG RemakeDisplay( VOID );
? LONG RethinkDisplay( VOID );
LONG GetScreenData( APTR buffer, ULONG size, ULONG type, CONST struct Screen *screen );
struct Screen *LockPubScreen( CONST_STRPTR name );
VOID UnlockPubScreen( CONST_STRPTR name, struct Screen *screen );
struct List *LockPubScreenList( VOID );
VOID UnlockPubScreenList( VOID );
STRPTR NextPubScreen( CONST struct Screen *screen, STRPTR namebuf );
VOID SetDefaultPubScreen( CONST_STRPTR name );
UWORD SetPubScreenModes( ULONG modes );
UWORD PubScreenStatus( struct Screen *screen, ULONG statusFlags );
struct Screen *OpenScreenTagList( CONST struct NewScreen *newScreen, CONST struct TagItem *tagList );
struct Screen *OpenScreenTags( CONST struct NewScreen *newScreen, ULONG tag1Type, ... );
struct ScreenBuffer *AllocScreenBuffer( struct Screen *sc, struct BitMap *bm, ULONG flags );
VOID FreeScreenBuffer( struct Screen *sc, struct ScreenBuffer *sb );
ULONG ChangeScreenBuffer( struct Screen *sc, struct ScreenBuffer *sb );
VOID ScreenDepth( struct Screen *screen, ULONG flags, APTR reserved );
VOID ScreenPosition( struct Screen *screen, ULONG flags, LONG x1, LONG y1, LONG x2, LONG y2 );

The two routines with the ? in front of them I'm assuming affect screens and may need to be incorporated somehow into my Display class, but I'm not sure and there wasn't much in the way of comments regarding them, so clues there would be appreciated.

I basically assumed anything with screen in it was something I needed to focus on. Is there anything I'm missing here? Someplace else I need to look? Again, clues appreciated.

Finally, I need to add events to such a class. Obvious events would be ones like: OnOpen(), OnClose(), OnRaiseLower(), OnMove, etc... Does anyone have any thoughts on these?

Thanks again.