/-------------------------------------------------------------------------\ | | | The ALLIANCE presents : Amiga Graphics Inside and Out from Abacus. | | | | This is the second in our series of complete books and due to the sheer | | size of it this one will be spread across the next 2 or 3 of our docs | | disks. | | | | Typed By RAZOR BLADE of Alliance. | | | | Greets to the rest of Alliance : | | | | Alchemist | | Asterisk | | Chaos | | Mit | | Shadowfax | | Viper | | | \_________________________________________________________________________/ ---------------------------------------------------------------------------- 3.4 THE INTUITION SCREEN. Intuition also manages screens. An intuition screen data structure is similar to those of intuition windows. The pointer to the screen data is located at offset 46 in the window data structure. To obtain the base address of your output window use the following: screen& = PEEKL(WINDOW(7)+46) To calculate the address of an individual data field you add the offset to the base address. The data structure is as follows: Data structure Screen/Intuition/342 bytes. Offset Type Description. ------- ------- --------------------------------------- +000 Long Pointer to the next screen. +004 Long Pointer to the first window in this screen. +008 Word X coordinate of upper left corner. +010 Word Y coordinate of upper left corner. +012 Word Width of the screen. +014 Word Height of the screen. +016 Word Y coordinate of mouse pointer. +018 Word X coordinate of mouse pointer. +020 Word Flags Bit 0 : 1 = Workbench screen. Bit 0-3: 1 = Custom screen. Bit 4 : 1 = Showtitle. Bit 5 : 1 = Screen beeps now. Bit 6 : 1 = Custom bit-map. +022 Long Pointer to screen name text. +026 Long Pointer to standard title text. +030 Byte TitleBar height. +031 Byte Vertical limit of titlebar. +032 Byte Horizontal limit of titlebar. +033 Byte Vertical limit of menus. +034 Byte Horizontal limit of menus. +035 Byte Top window border. +036 Byte Left window border. +037 Byte Right window border. +038 Byte Bottom window border. +039 Byte Unused. +040 Long Pointer to standard font TextAttr +044 -- Viewport of screen. +084 -- Rastport of screen. +184 -- Bit-map of screen. +224 -- LAyerInfo of screen. +326 Long Pointer to first screen gadget. +330 Byte DetailPen. +331 Byte BlockPen. +332 Word Backup register for Beep(), stores col0 +334 Long Pointer to external data. +338 Long Pointer to user data. You probably noticed that the window and screen data structures are quite similar, even though some fields are new. Again, we will explain each field individually. PAGE 114 ---------------------------------------------------------------------------- 3.4.1 SCREEN STRUCTURE. OFFSET 0: NEXT SCREEN. Screens are also organised by Intuition in the form of a data chain. When there are other screens in a chain with your screen, the address of the next screen's data block is at this offset. OFFSET 4: FIRST WINDOW. Remember the data chain used by windows: two fields, the father and child, provide the address of the previous and next windows. By using these you can move back and forth through the chain from one window to another. however, this method has a small flaw. In order to go through the entire chain, you have to find the beginning of the chain first. The active window you access is not necessarily the first window in the chain. If you are interested only in a window in a specific screen, there is an easier method you can use. This field contains the address of the first window data block. The address of the next window structure is in offset+0 of the window data structure. windo& = WINDOW(7) scr& = PEEKL(windo&+46) searcher&=scr&+4 WHILE flag% = 0 searcher& = PEEKL(searcher&) IF searcher& = 0 THEN flag% = 1 ELSE counter%=counter%+1 PRINT "Window";counter%; PRINT " Data block address : "; PRINT searcher& END IF WEND END NOTE: Although this method is easier to program, it only accesses those windows in the output window of the current screen. PAGE 115 ---------------------------------------------------------------------------- OFFSET 8, 10, 12 AND 14: SCREEN DIMENSIONS. Like the window structure, there offsets contain the coordinates of the upper left hand corner of the screen and the height and width of the screen. The corner coordinate is relative to the top corner of the display. The current versions of the Amiga(500-2000) do not allow horizontal shifting of the screen. Offset field +8 is available for future compatibility. OFFSET 16 AND 18: THE MOUSE COORDINATES. Here you find the X and Y coordinates of the mouse pointer relative to the upper left hand corner of the screen. During vertical screen movements the Y value can vary a bit. OFFSET 20: FLAGS. The bit descriptions a self-explanatory. Show title means that the screen's title text is visible. A custom bit-map is suitable when you are generating a new screen that has its own drawing plane. OFFSET 22 AND 26: THE NAME OF THE SCREEN. This offset contains the address of either the name string of this screen or a standard text string which is taken as default from a window when a name string is not specified. OFFSET 30-39: DEFAULT PARAMETERS. These bytes contain various standard parameters, such as the dimensions of the title bar etc.. All windows in this screen default to these dimensions automatically. OFFSET 40: THE STANDARD CHARACTER SET. Whenever a window is opened in your screen, it has a standard character set (a predetermined font). The address of this font is stored here. We will be discussing character sets in more detail later. PAGE 116 ---------------------------------------------------------------------------- OFFSET 44 : THE VIEWPORT. This is another new term we will be discussing in more detail later. In relation to the data structure of the screen, the ViewPort is NOT a pointer. At offset 44, it is the actual ViewPort of the screen. ViewPort, which is a small data structure 40 bytes long, is an interface to the Amiga graphic hardware (the COPPER graphic coprocessor). OFFSET 84: THE RASTPORT. This offset is not a pointer either but the actual RastPort. You received an introduction to the RastPort in the window data structure. Since both screen and windows are drawing planes, the screen also has a RastPort. OFFSET 184: THE BIT-MAP. This is a new data structure which is 40 bytes long. Bit-map is the interface between the screen and the memory it occupies, called "bit-planes". OFFSET 234:THE LAYERINFO. This is the last internal data structure of the screen. It is the core of thw windowing system (the layers). This will be discussed in detail later. OFFSET 326: POINTER TO SCREEN GADGETS. Screens also recognise gadgets that move them to the background or bring them to the foreground. This field is specifically for internal system use. OFFSET 330 AND 331: THE SCREEN COLOURS. Changing the screen colour values that are stored here works the same way as for windows. The new colours take effect as soon as the screen is refreshed, such as when you use a menu etc... OFFSET 332: BACKUP-REGISTER. Intuition stores the colour from register 0 here when the screen is flashed or beeped. The following will beep the screen: PRINT CHR$(7) OFFSET 334 AND 338: EXTERNAL AND USER DATA. These allow the possibility to link other data blocks with the standard structure. PAGE 117 ---------------------------------------------------------------------------- 3.4.2 THE INTUITION FUNCTIONS FOR SCREEN HANDLING. Below are the routines from the intuition library used for screen handling: MoveScreen() ScreenToBack() ScreenToFront() WBenchToBack() WBenchToFront() To make things easier we have written three SUBs that use all of these routines. They are named ScrollScreen, ScreenHere and ScreenBye. ScrollScreen requires the number of pixels that the screen should scroll down in the current output window (a negative value scrolls it up). ScreenBye sends the screen behind all current screens and ScreenHere brings the screen to the foreground. Here are the SUBs in a small demonstration program: '##################################### '# '# Section: 3.4.2 '# Program: Screen Control. '# Date : 01/04/87 '# Author : tob '# Version: 1.0 '# '###################################### ' Program controlled screen handling. PRINT "Searching for .BMAP file ........." 'INTUITION-library 'MoveScreen() 'ScreenToFront() 'ScreenToBack() LIBRARY "intuition.library" init: CLS SCREEN 1,320,200,1,1 WINDOW 2,"Hello1",,,1 main: '* Screen scrolling. PRINT "This is the second screen! " PAGE 118 ---------------------------------------------------------------------------- '* Screen 1 down. WINDOW OUTPUT 2 FOR loop% = 255 TO 0 STEP -1 ScrollScreen(1) NEXT loop% '* Screen 0 Down. WINDOW OUTPUT 1 FOR loop% = 255 TO 0 STEP -1 ScrollScreen(1) NEXT loop% '* Screen 1 up. WINDOW OUTPUT 2 FOR loop% = 0 TO 255 ScrollScreen(-1) NEXT loop% '* Screen 0 up. WINDOW OUTPUT 1 ScreenHere FOR loop% = 0 TO 255 ScrollScreen(-1) NEXT loop% '* Swapping. FOR t% = 1 TO 3000:NEXT t% ScreenBye FOR t% = 1 TO 3000:NEXT t% ScreenHere FOR t% = 1 TO 3000:NEXT t% '* Closing. WINDOW CLOSE 2 SCREEN CLOSE 1 endprog: LIBRARY CLOSE END SUB ScrollScreen(pixel%) STATIC screenAddress&=PEEKL(WINDOW(7)+46) CALL MoveScreen(screenAddress&,0,pixel%) END SUB SUB ScreenHere STATIC screenAddress& = PEEKL(WINDOW(7)+46) CALL ScreenToFront(screenAddress&) END SUB SUB ScreenBye STATIC screenAddress& = PEEKL(WINDOW(7)+46) CALL ScreenToBack(screenAddress&) END SUB PAGE 119 ----------------------------------------------------------------------------