Intuition ~~~~~~~~~ Before continuing with gadgets, I am going to briefly cover Intuition Screens. This tutorial will serve only as an introduction as I`m running out of time. Screens ~~~~~~~ To date, all the Intuition tutorials have dealt with windows opened on the Workbench screen. This has it`s advantages, no extra memory is required for a custom screen and the examples are all visible on the screen a text viewer can run on should you wish to read and experiment at the same time. The major drawback is colour. Workbench is limited to four colours. Something I have neglected to mention so far is that Images and Borders can be rendered in as many colours as the screen provides. Imagine the contrast available with a sixteen colour display! You could open several windows, each with different foreground and background pens. You could add multi-coloured gadgets and Images and build a display more worthy of your beloved Amiga. So how does one open a screen? If your thinking ` structures `, your right. A screen structure needs to be defined and then this is supplied to OpenScreen(). OpenScreen() returns a pointer in the same way as OpenWindow() which should be tested and saved for later use. The New Screen Structure ======================== ns_LeftEdge WORD x origin ns_TopEdge WORD y origin ns_Width WORD width in pixels ns_Height WORD height in lines ( pixels ) ns_Depth WORD number of bitplanes ns_DetailPen BYTE foreground pen ns_BlockPen BYTE background pen ns_ViewMode LONG display modes flags ns_Type LONG screen type flags ns_Font LONG pointer to TextAttr, NULL for default ns_DefaultTitle LONG pointer to title string ns_Gadget LONG pointer to gadget list ns_BitMap LONG pointer to CustomBitMap, NULL default I will now explain each field in a little more detail. LeftEdge ~~~~~~~~ Not implemented in kickstart 1.3 or lower, set to zero. TopEdge ~~~~~~~ Number of scan lines from top of display before the start of the screen. This will normally be set to zero and leave it up to the user to reposition the screen. Width ~~~~~ The pixel width of the screen. Though you can try other values, the recommended ones are: 320 for low resolution, 640 for high resolution. Height ~~~~~~ The height in scan lines of your display. Again it is normal to use 256 ( 200 ) for non-interlaced and 512 ( 400 ) for interlaced displays. Depth ~~~~~ Number of bitplanes to use for the screen, may take a value from 1 to 6. DetailPen ~~~~~~~~~ The colour to use for foreground drawing/text printing. BlockPen ~~~~~~~~ The colour to use for background drawing/text printing. ViewModes ~~~~~~~~~ The fun bit. Tells Intuition what display mode to use. A particular mode is defined by setting the appropriate bits in this long word flag. Each flag is easiest referred to by name: V_HIRES hi resolution mode ( 640 width ) V_LACE interlace mode on V_SPRITES enable sprites in this display V_DUALPF dual playfield mode V_HAM hold and modify mode V_EXTRA_HALFBRITE 64 colour mode GENLOCK_VIDEO this allows normal display mode. Note that some modes are best set up by altering a screen once opened in a lesser mode, for example dual playfield. First open a normal screen and then add the dual playfield. Type ~~~~ Defines the type of screen. Those I know about are: CUSTOMSCREEN all screens you open will be custom screens, so set this bit. SCREENBEHIND opens the screen behind all other screens. SCREENQUIET screen will not have a title bar or gadgets visible. CUSTOMBITMAP set this if you are using your own bitplanes. For this tutorial I am only going to use CUSTOMSCREEN. Font ~~~~ A pointer to a TextAttr structure that defines the font to be used in all window title bars and menu entries. For the present, set this to zero for the default Intuition font. DefaultTitle ~~~~~~~~~~~~ A pointer to the title to be displayed in the screens title bar. Note that the title text must be null terminated. Gadgets ~~~~~~~ Not implemented on kickstart 1.3 or lower. Set to zero. CustomBitMap ~~~~~~~~~~~~ Pointer to a BitMap structure if you are supplying your own bitplanes for the screen display. Will cover this in a later tutorial. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Opening A Screen ~~~~~~~~~~~~~~~~ Opening a screen is just a case of setting up a new screen structure and then calling OpenScreen(). The new screen will then be displayed. OpenScreen() supplies a pointer to the Screen structure if all went ok. If OpenScreen() fails to open the screen, it returns zero. You should always test register d0 for the return value. When you have finished with the screen you should close it by calling CloseScreen(). This requires the pointer returned by OpenScreen(). The following fragment demonstrates this: lea MyScreen,a0 CALLINT OpenScreen move.l d0,scrn.ptr beq.s Error << more program here >> move.l scrn.ptr,a0 CALLINT CloseScreen << more program here >> MyScreen dc.w 0,0 x,y origin dc.w 320,256 width,height dc.w 3 3 planes = 8 colours dc.b 3 foreground colour dc.b 1 background colour dc.l GENLOCK_VIDEO view modes: normal dc.l CUSTOMSCREEN screen type dc.l 0 default font dc.l ScrnName pointer to title dc.l 0 no gadgets dc.l 0 no custom bitmap Once a screen has been opened, you can open windows on it. Opening Windows ~~~~~~~~~~~~~~~ Windows are opened in the normal way. The only extra step required is to put a pointer to the screens structure ( returned by OpenScreen ) in the nw_Screen field of the New Window structure and also set the nw_Type field to CUSTOMSCREEN. This is best seen by looking at an example. See the ColourGadget program in my source directory. It opens a custom screen, then a window and displays a gadget, in eight colours, in the window. Note that no extra work is required for the gadget. As I`m so pushed for time, that`s all I`ve got time for this month. Will expand on screens next month. Mark.