Difference between revisions of "AGI/Specifications/Logic"

    * Number (no prefix)

    * Var (prefix ``v'')

    * Flag (prefix ``f'')

    * Message (prefix ``m'')

    * Object (prefix ``o'')

    * Inventory Item (prefix ``i'')

    * String (prefix ``s'')

    * Word (prefix ``w'')

    * Controller (prefix ``c'')

    The value of the variable n is incremented by one, i.e. vn = vn+1. If the value is already 255, it is left unchanged.

    The value of the variable vn is decremented by one, i.e. vn = vn-1. If the value is 0, it is left unchanged.

    Variable vn is assigned the value m, i.e. vn = m

    Variable vn is assigned the value of vm, i.e. vn = vm.

    The value of variable vn is incremented by m (vm), i.e. vn = vn + m (vm).

    If the value is greater than 255 the result wraps over 0 (so 250 + 10 == 4). (Information by XoXus)

    The value of vn is decremented by m (vm), i.e. vn = vn - m (vm).

    If the value is lesser than 0 the result wraps (so 1 - 2 == 255). (Information by XoXus)

    Variable vi where i is the value of vn is assigned a value m, i.e. Var(vn) = m.

    Variable vi where i is the value of vn is assigned the value of vm, i.e. Var(vn) = vm.

    Variable vn is assigned the value of vi where i is the value of vm, i.e. vn = Var(vm).

    Variable vn is multiplied by m, i.e. vn = vn * m.

    Variable vn is multiplied by the value of vm, i.e. vn = vn * vm.

    Variable vn is divided by m, i.e. vn = vn / m.

    Variable vn is divided by the value of vm, i.e. vn = vn / vm.

    (What happens on division by 0? --VB)

    Variable vk is assigned a random value in the range between n and m. Now let us consider the commands changing flag values. Remember that a flag can only have a value 0 or 1.

    fn is set to 1.

    fi, where i is the value of vn, is set to 1. i.e. flag(vn) = 1.

    fn is set to 0.

    fi, where i is the value of vn, is set to 0, i.e. flag(vn) = 0.

    fn toggles its value.

    fi, where i is the value of vn, i.e. flag(vn), toggles is value.

    Load into memory the LOGIC resource number n, i.e. Logic(n)

    Load into memory the LOGIC resource number i, where i is the value of vn, i.e. Logic(vn)

    Loads into memory the PICTURE resource number i, where i is the value of vn, i.e. Picture(vn)

    (This may be a mistake in the original: I would expect this command to be load.pic.v, while load.pic(n) would load resource number n. --VB)

    (load.pic.v may be a more appropriate name for it, but the name above is what they gave it. There is no equivalent command that takes a number rather than a variable. --LE)

    Loads into memory the VIEW resource number n, i.e. View(n).

    Loads into memory the VIEW resource number i, where i is the value of vn, i.e. View(vn)

    Loads into memory the SOUND resource number n, i.e. Sound(n).

    (Note that there is no load.sound.v listed. I wonder if this is a mistake or there really is no way to load a sound with indirection (unlikely, I think) --VB)

    (There really is no way of loading a sound with indirection. The command doesn't exist. --LE)

    Unloads PICTURE resource number i, where i is the value of vn.

    Unload VIEW resource number n, i.e. View(n).

    Unloads VIEW resource number i where i is the value of vn, i.e. View(vn).

    (And what about discard.logic, discard.logic.v, discard.sound, and discard.sound.v? --VB)

    (There must be some other way that those commands are removed from memory, because the commands you mention above don't exist. --LE)

    These commands do the following:

      1. Commands stop.update and unanimate are issued to all objects;

      2. All resources except Logic(0) are discarded;

      3. Command player.control is issued;

      4. unblock command is issued;

      5. set.horizon(36) command is issued;

      6. v1 is assigned the value of v0; v0 is assigned n (or the value of vn when the command is new.room.v); v4 is assigned 0; v5 is assigned 0; v16 is assigned the ID number of the VIEW resource that was associated with Ego (the player character).

      7. Logic(i) resource is loaded where i is the value of v0 !

      8. Set Ego coordinates according to v2:

              * if Ego touched the bottom edge, put it on the horizon;

              * if Ego touched the top edge, put it on the bottom edge of the screen;

              * if Ego touched the right edge, put it at the left and vice versa.

      9. v2 is assigned 0 (meaning Ego has not touched any edges).

      10. f5 is set to 1 (meaning in the first interpreter cycle after the new_room command all initialization parts of all logics loaded and called from the initialization part of the new room's logic will be called. In the subsequent cycle f5 is reset to 0 (see section Interpreter work cycle and the source of the ``Thunderstorm'' program. This is very important!).

      11. Clear keyboard input buffer and return to the main AGI loop.

    LOGIC resource number n (or number i where i the value of vn) is executed as a subroutine. If the logic with the given ID is not loaded in memory, it is temporarily loaded and discarded after returning from the call (this takes extra time). call does not change any variables or flags.

    This command returns control to the interpreter if it is executed in Logic(0), or to the command following the call command which called the current logic.

    This command unconditionally transfers control to a command starting after label label within the same logic.

    Normally, when a logic is called using call command, execution begins at the first instruction. set.scan.start command sets the entry point at the command following it, while reset.scan.start returns the entry point to the beginning.

    * If an object priority is 0 it cannot cross an unconditional barrier (pixels with priority 0).

    * If an object priority is 15 and a command ignore.block has not been given to it, it cannot cross a conditional barrier (pixels with priority 1) and leave the block set using the block command.

    * If an object has not been given ignore.horizon command, it cannot move above the horizon set using the set.horizon command.

    * An object should follow the conditions set using object.on.water and object.on.land commands (see below).

    Object number n is included in the list of object controlled by the interpreter. Objects not included in that list are considered inexistent!

    All objects are removed from the control list and are considered inexistent.

    Object n is associated with a VIEW resource number m (or pointed to by vm), which may be an image of the object.

    Chooses a loop m (or vm) in the VIEW resource associated with the object n.

    Turns off automatic choice of loop number for the object number n.

    <pre>Turns on automatic choice of loop number depending on the direction of motion of the object n.

 

 

    Automatic choice of the loop is done according to the table:

 

        * for objects with fewer than 4 but more than 1 loops:

        * for objects with more than 4 loops:

 

    x means that the current loop number is retained.</pre>

    Selects a cel m in the current loop of the object n.

    The number of the last cel of the current loop of the object n is stored in vm.

    The number of the current cel of the object n is stored in vm.

    The number of the current loop of the object n is stored in vm.

    The number of the current VIEW resource associated with the object n is stored in vm.

    Set priority of the view of the object n to m (or vm).

    Turns on the automatic priority choice for the object n. The priority is set depending on the vertical coordinate of the object. This way, as an object moves down it approaches the viewer. See section Priority bands and control lines for a table of y coordinates and the associated priorities.

    The value of the current priority of the object n is stored in vm.

    Coordinates of the object n, not yet displayed on the screen, are set to x and y (or vx and vy).

    Object n is shown on the screen. The image uses the values of the loop and the cel in the VIEW resource associated with the object n (see set.view), as well as the priority and coordinates of the object. If a command start.cycling is also issued, a looped animation for object n is shown until stopped (for example, with stop.cycling).

    Object n is erased from the screen.

    Coordinates of the object n are stored in vx and vy. Coordinates of the object are coordinates of the base point (bottom left corner) of cels of the VIEW resource associated with the object.

    The interpreter automatically plays the animation (a loop in the VIEW resource) associated with the object, starting at the specified cel. The following commands control this process.

    Enables automatic change of cels in a chosen (using set.loop) loop of a VIEW resource associated with the object n (using set.view).

    Disables automatic change of cels in a chosen (using set.loop) loop of a VIEW resource associated with the object n (using set.view).

    Cels of the loop associated with the object n follow in a normal order: 0, 1, 2, ..., k-1, 0, 1, 2, ...

    Cels of the loop associated with the object n follow a reverse order: k-1, k-2, ..., 1, 0, k-1, k-2, ..., 1, 0, ...

    Plays the loop associated with the object n once, from the current cel to the last. When finished, fm is set to 1.

    Plays the loop associated with the object n once in a reverse order, from the current cel to the first. When finished, fm is set to 1.

    vm sets the time in interpreter cycles between cel changes for the object n. When vm = 1 cels are changed every cycle.

    Set the horizon to y = n.

    Object n moves regardless of the horizon position.

    Object n cannot move above the horizon.

    Sets a rectangular area (block).

 

    Cancels previously set block.

    Object n moves ignoring conditional barriers (pixels with priority 1) and a block set with the block command.

    Object n may not cross conditional barriers or leave the block.

    Object n moves regardless of positions of other objects.

    Object n treats other objects as obstacles.

    The player is allowed to control Ego (object number 0) using the keyboard or the joystick.

    The player is not allowed to control object 0 (Ego).

    Motion of object n is stopped. If n == 0, program.control is automatically executed.

    Motion of object n is started. If n == 0 (Ego), player.control automatically executed.

    vn determines the number of pixels the object n moves each step. (The actual value in pixels is the step size / 4! --CM)

    vn determines the speed of object n motion: delay in the interpreter cycles between consecutive steps. If vm = 1, step occurs on every cycle.

    Object n is told to move to the point (x,y) (or vx, vy) by s pixels every step. When the destination is reached, fm is set to 1. If n == 0 (Ego), program.control is executed automatically.

    Object n is told to chase object 0 (Ego) by s pixels every step. When Ego and object coordinates become equal, fm is set to 1.

    Object n randomly changes the direction of its motion (wanders). If n == 0 (Ego), program.control is issued automatically.

    Special object motion mode is canceled. The object continues to move in the direction it was moving in at the time the command was issued.

    Object n is told to move in the direction vm.

 

    Direction of object n motion is stored in vm.

    Object n is allowed to be only in the area where its base line is completely on pixels with priority 3 (water surface).

    Object n is not allowed to touch pixels of water surface (priority 3).

    Motion restrictions previously set on the object n with commands object.on.water or object.on.land are cancelled.

    Object n jumps from its current location into the location with coordinates (x + vdx, y + vdy).

    (Shouldn't there be reposition and reposition.v? --VB)

    (There should be, but they don't exist. --LE)

    Similar to the preceding command, but the object is moved to the point x, y (vx,vy).

    Object n is removed from the list of objects updated by the interpreter on each step. The object stays on the screen unchanged.

    Object n is redrawn on each interpreter step.

    Object n is redrawn immediately, without waiting for the end of the interpreter cycle.

    If both objects n and m are on the screen, then

    otherwise vd = 255.

    Stores 255 in room field of an object n, which means that the player owns it.

    Stores 0 in the room field of object n.

    Stores the value m (or vm) in the room field of the object n.

    Stores the value of the room field of object vn in vm.

    The screen is switched to text mode; the top line displays ``You are carrying:'', then the names of the object with room field equal to 255 are listed. If there are no such objects, the word ``nothing'' is displayed.

    If f13 is set (allow item selection), a highlight appears which allows the player to select an item name. When ENTER is pressed, the selected object number is stored in v25. When ESC is pressed, 255 is stored in v25.

    A PICTURE resource number i, where i is the value of vn is executed. As the result, the background picture is created in the internal buffer of the interpreter. Before execution, the buffer is cleared, i.e. all pixels are set to colour 15 and priority 4.

    Just like the above, only the internal buffer is not cleared before drawing. Picture(vn) is drawn over the existing picture.

    A picture of a VIEW resource is added to the background as its component. Typically, this is used to add small complicated details which would require too many PICTURE resource commands to draw.

    Parameters are:

        * a (va): number of the VIEW resource;

        * b (vb): loop number;

        * c (vc): cel number;

        * d (vd): x coordinate;

        * e (ve): y coordinate;

        * f (vf): priority;

        * g (vg): margin.

    If margin is 0, 1, 2, or 3, the base of the cel is surrounded with a rectangle of the corresponding priority. If margin > 4, this extra margin is not shown.

    Shows internal buffer on the screen.

 

    Any other order may crash the interpreter without any diagnostic messages.

Sound resource management commands

    Starts playback of the SOUND resource number n. When finished, fm is set to 1.

    Stops the playback.

    Prevents the user from entering anything using the keyboard.

    Allows the user to enter text using the keyboard.

    Opens a text window in the centre of the screen, where a message number n (or vn) from the messages field of the current LOGIC resource is displayed. Output mode is determined by f15 (see flag description). The message is a NULL-terminated string of text. In addition to letters, digits, and other symbols, the string may contain:

        * Newline character (0x0A);

        * Format element:

              o %v<decimal number>: at this place the output will include a decimal value of variable with the given number.

              o %m <number>: the text of the message with the given number is inserted at this place.

              o %0 <number>: the name of the item with the given number is inserted at this place.

              o %w <number>: a vocabulary word with the given number is inserted at this place.

              o %s <number>: a string variable with the given number is inserted at this place.

              o %g <number>: a message with this number from message field of Logic(0) is inserted at this place.

    For %v, you can add a vertical line and a number of characters the output should take. In this case leading zeros are not suppressed in the output.

    When you write your messages, remember that the interpreter wraps the text between the lines as needed when the message is displayed.

    Prints a message number n (vn) in the row r (vr), starting with the column c (vc). No window is created, so it is up to the programmer to erase the output when it is no longer needed.

    Analogous to print but the programmer can specify the window location. x, y, and l are constants specifying coordinates of the top left corner of the window and its width in character cells of a 40x25 screen.

    Prints interpreter version in the centre of the screen.

    The screen switches to the text mode 40x25.

    The screen returns to the graphics mode. The picture on the screen is restored.

    First byte of the message n is used as a text mode cursor.

    Sets foreground and background colours for display, get.num and get.string commands.

    Clears text lines from n to m using colour c.

    Clears a rectangular area with top left corner coordinates (x1,y1) and bottom right coordinates (x2,y2) using colour c.

    Shows the status line containing the current score and sound status (on/off).

    Removes the status line.

    Stores message number m in the string variable n.

    Word number m of the user input is stored in sn.

    User input is stored in sn. m is the number of the message used as the prompt. x, y and l are input position and maximum string length.

    Parses sn as if it was entered by the player.

    Enters a number from the keyboard into vm. Message n is used as the prompt.

    Set interpreter's special key. c is the key code (decimal number from 0 to 255) and s (if the key is a regular, or CTRL+key pair). the ASCII code (for example, TAB is 0x0009). If the key is a function key or ALT+key pair, the corresponding IBM-PC keyboard scan code is in the high byte of s. For example, the scan code of F1 is 0x3B00, ALT+Z is 0x2C00.

    Does ``key code'' mean the key scan code, or the ASCII code of the character? Is the IBM-PC scan code valid in other platforms as well? -- CM

    Message n is scanned by the interpreter and compared with its internal identifier. On mismatch, the program exits. For the AGDS interpreter the identifier is ``TQ''. See also section Game IDs.

    Sets the size of script table in bytes. Script table stores codes of some interpreter commands. It is needed by the interpreter to correctly reload resources when restore_game is executed.

    Sets the built-in debugger parameters. n is the number of LOGIC resource with command names, and m and l are the first line and height of the debugger window.

    Turns on the debugger. In general, the debugger is turned on with SCROLL LOCK key when the command name table is loaded even if this command does not occur in the program.

    This is a debugging command. It writes a log message in the format

 

    where the message is given by number n. Output is sent to a file.

    (Are these debugging commands valid only for AGDS, or they work in AGI as well? --CM)

    Message n is used as the header of the menu elements which follow.

    Message n is used as a menu element, where c is this element's code (a number between 0 and 255).

    Ends menu creation.

    Enables or disables a menu item with the code c.

    If f14 is set, a menu system is shown on the screen, allowing the user to choose an item. Whether an item with the code c has been chosen can be tested using a command controller(c), where c is the code assigned to the menu item.

    TRUE if vn = m.

    true if vn = vm.

    TRUE if vn < m.

    TRUE if vn < vm.

    TRUE if vn > m.

    TRUE if vn > vm.

    TRUE if fn is set.

    TRUE if Flag(vn) is set.

    TRUE if the room field of item n is 255, i.e. the item belongs to the player.

    TRUE if room field of the object n is vm.

    TRUE if the coordinates of the base point of the cel which is the current image of object n satisfies the equations x1 <= x <= x2 and y1 <= y <= y2.

    TRUE if the base of the object n is completely within the rectangle specified using its top left (x1,y1) and bottom right (x2,y2) corners.

    TRUE of the center of the base line of the object n is inside the rectangle specified as its top left and bottom right corners.

    TRUE of the right side of the base line of the object n is inside the rectangle specified as its top left and bottom right corners.

    TRUE if the user has pressed any key on the keyboard. Used to create cycles to wait until any key is pressed.

    TRUE if s1 == s2.

    where i = 1, ..., n.

    See section Player input parsing.

    TRUE if the event with code n has occurred:

        * a key with the code n was pressed (set using set_key);

        * menu item with code n was selected in command menu_input.

    Sets position of lines on the screen, where a = 1 (the minimum line number for print), b is the user input line and c is the status line.

    (Sounds confuse --CM)

    Prints a message for the object vn in the format

 

    Displays a report of the interpreter memory status.

    Shows priorities of the screen pixels. Priority n is shown as color number n (see color setting commands in I.1.2.1.1).

    Show cel 0 of loop 0 of the VIEW resource n in the bottom center of the screen. In the center of the screen, a message associated with the VIEW resource is printed.

    (That's what they say but I suspect they mean OBJECT n, not VIEW resource. --VB)

    (Actually, in this case the argument does refer to the VIEW resource. This is because the VIEW in question isn't meant to be a controlled object but instead is simply the picture and textual description of the an inventory item. --LE)

    The screen shakes n times.

    The last line entered by the user is displayed in the input line.

    Input line is cleared.

    If there is a text window on the screen, it is removed.

    Enables and disables get.string and get.num commands if prevent.input has been issued.

    Restarts the game from the very beginning.

    These command save and restore the current state of the game into disk files.

    Stops the interpreter until any key is pressed.

    Exits the interpreter. If n = 1, quits immediately. If n = 0, asks ``Press ENTER to quit. Press ESC to continue.''

    Initialize joystick.

    Switch RGB monitor into the graphics mode.

    Usually the crossing by an object of various areas and lines is tracked by the base point (bottom right corner) of its cel. After this command, top left corner is used as such a point.

    This command modifies the behavior of the commands restore.game() and save.game().

    After calling unknown170(n), where n is a string number (ie: if n == 2 then s2) restore.game() will automatically (without any prompt) restore a savegame with the name stored in string number n and save.game() will automatically save a savegame with the name of string number n.

    Note: make sure that at least one savegame is present when you call restore.game() or save.game() (that is, when saving a game too).

 

    will automatically load the savegame named ``test''.</pre>

    Note: AGI256 uses this command

    This command changes the way that ego is controlled. After calling unknown173(), Ego will only move when a direction key is maintained pressed. If the key is released, ego will stop walking. See also command unknown181().

    This command control the access to the menu. unknown177(0) will disable access to the menu, even if flag 14 (menu_enabled) is set. Calling unknown177() with a value greater than 0 seem to do nothing else than enabling access to the menu.

    This command restablishes the default control of Ego. It is normally used after a call to unknown173().

Note: Be aware that commands 175, 176, 178, 179 and 180 of the last version of AGI (ver 3.002.149) do absolutely nothing.