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Retro style 2D game engine using crustyvm as a scripting engine.
License: GNU General Public License v3.0
This project forked from paulguy/crustygame
Retro style 2D game engine using crustyvm as a scripting engine.
License: GNU General Public License v3.0
BUILDING To compile crustygame, just type `make`. You'll need SDL 2 and gcc, but aside from that, there should be no other dependencies. To optionally compile the BMP converter, use `make -f Makefile.bmpconvert`. RUNNING `./crustygame [-D<var>=<value> ...] <scriptname>` Some scripts may define variables to be set on the command line for modifying various options. If a script has captured the mouse, CTRL+F10 can be pressed to release it. CTRL+F10 will have to be pressed again to allow the script to recapture the mouse. METADATA Metadata may be provided to crustygame in a comment on the absolute beginning of the program. the comment must read ";crustygame ", and only data provided on this one line will be used as metadata. There is only one metadata item supported at the moment: save:<size> Specify that the script should have persistent save storage of <size> bytes. THE LANGUAGE Before anything is done, a pass is made to find all the tokens in the program. Quoted strings act as a single token. Comments are thrown out at this stage. Comments begin with a ; and include everything following. Quoted strings may contain ;s though. At this point, only one statement is meaningful: include <filename> Read in the file <filename> in the root directory of the script and start parsing tokens in from this file. Care is taken that files above the script directory should be inaccessible to be included in to a script for safety reasons, but don't rely on it for security. Make reasonably sure like any other program or script that you trust where it came from. Preprocesor Statements The first step to a program running (after it's tokenized) is to run through and interpret the preprocessor statements, which are responsible for defining preprocessor-time variables, and rewriting statements based on those. Any time a single argument is needed to have spaces, it must be enclosed in quotes, otherwise it'll be interpreted as multiple arguments. Quoted strings support the following escape sequences: \r carriage return \n new line \<carriage return> ignore a carriage return in the string. A following new line is also ignored \<new line> ignore a new line in the string. A following carriage return is also ignored \\ a literal \ (backslash) \xNN - a two digit hex number representing a byte literal \" a literal " (quote) macro <name> [arguments ...] Start a macro definition. From here, lines will be passed over until until and endmacro statement with the same name is reached, at which time normal interpretation will resume. The arguments are a list of symbols which when the macro is evaluated, will be replaced by whatever values were passed in when invoked. endmacro <name> End the named macro definition. Normal interpretation will resume. if <number> <name> [arguments ...] If <number> is non-zero, start copying the named macro with the listed arguments. <number> may also be an expression which is to be replaced by an expression or a macro argument, or it may also be a variable passed in on the command line with -D, in this case, it'll always evaluate to true, even if the variable is specified to be 0. expr <variable> <expression> Evaluate an expression down to a numerical value and assign it to <variable>. At that point, any time <variable> appears in the program, it'll be replaced by the value which the expression evaluated to. An expression can only accept integer values and all operations are done as integers and the result is an integer. Expressions are arithmetic statements and support the following operators: * multiplication / division % modulo + addition - subtraction << binary shift left >> binary shift right < logical less than <= logical less than or equal > logical greater than >= logical greater than or equal == logical equals != logical not equals & bitwise AND !& bitwise NAND | bitwise OR !| bitwise NOR ^ bitwise XOR !^ bitwise XNOR Parentheses are also supported for grouping, otherwise it follows the precedence followed is similar to that of C arithmetic parsing precedence. <macroname> <arguments ...> Start evaluaing (copying) from macro and continue until the matched endmacro is reached. Replacing any argument values with the arguments passed in. All arguments specified must be provided. Symbol Definition Statements Following the preprocessing stage, the resulting code is scanned to find symbol definitions: procedures, global (static) variables and procedure (local) variables. Before this begins though, any callback variables defined by the VM will be added in as globals. proc <name> [arguments ...] Defines the start of procedure <name> and specifies which arguments, if any, it accepts. Those arguments become local variables which reference the memory of the variables passed in, that is, any modifications to them in the procedure will persist when the procedure returns. ret Return from procedure. Marks the end of a procedure. static <name> [N | ints <N | "N ..."> | floats <N | "N ..."> | string "..."] Define a global (static) variable <name>. If a single number is provided, it will act as a single integer initializer. If a type is specified, a single value may be provided to create an array of that size, otherwise, multiple arguments may be specified in quotes, separated by spaces or tabs, to create an array of the size of values given and initialized with those values. The exception is string, which can only be initialized with a single argument, quoted or not. Values are initialized once, on VM start. These may be specified anywhere, procedure or not. local <name> [N | ints <N | "N ..."> | floats <N | "N ..."> | string "..."] Define a procedure (local) variable <name>. The initializer is specified in the same way as global variables. These values are initialized on each call to a procedure. These can only be defined inside procedures. Procedure variables must have unique names to global variables. stack Not a real instruction, just indicate to accumulate stack. label Define a label within a procedure to jump to. Label names are scoped locally to procedures. binclude <name> <chars | ints | floats> <filename> [start] [length] Read in <filename> to be the initializer for a global variable <name>. The type must be defined as chars (a string), ints (integer array) or floats (double array). A start byte and length byte may be specified to include only a particular range of the file. As many items of the size of type which fit within the file or provided length will be read in and used as the array initializer. Like include, some care is taken to prevent arbitrary files above the script's directory from being read in. The same warning applies. Program Instructions The final stage is parsing instructions and generating bytecode. The language supports a fairly limited set of instructions, but ones which vaguely represent the selection of instructions one may have available on a more primitive platform, just with some added feature and artistic license for the sake of simplciity and safety, but bugs can certainly still come up. move <destionation>[:<index>] <source>[:<index>] Simply move a value from source to destination. Source may be a variable, an integer immediate or a callback with the index passed to it, which will return a value. Values will be converted to the type destination is before being stored. If destination is a callback itself, it will be passed a reference to the source at the index provided, assuming it's not also a callback or an immediate, in which case only the single value ia passed in. All indexes are range checked to avoid hidden out of bounds accesses, in which case the program is terminated. A read or write callback indicating an error will also terminate execution. An index of 0 is implied if it's excluded. add <destination>[:<index>] <source>[:<index>] Add <destionation> at <index> and <source at <index> then store the value in <destination>. Source may be a callback in this case but destination cannot be, even if a callback may otherwise be readable and writeable. If either destination or source is a float value, the operation will be done as if they are floats, but will be converted to the type of the destination, truncated to the range/precision of the type. All other arithmetic operations follow similar rules. sub <destination>[:<index>] <source>[:<index>] Subtract. mul <destination>[:<index>] <source>[:<index>] Multiply. div <destination>[:<index>] <source>[:<index>] Divide. mod <destination>[:<index>] <source>[:<index>] Modulo (remainder). and <destination>[:<index>] <source>[:<index>] Bitwise AND. Bitwise instructions follow similar access rules as arithmetic expressions, but they are restricted to operating on integer or string types. A character of a string is converted to a 32 bit integer and padded out with 0s in its most significant bits. or <destination>[:<index>] <source>[:<index>] Bitwise OR. xor <destination>[:<index>] <source>[:<index>] Bitwise XOR. shr <destination>[:<index>] <source>[:<index>] Bitwise shift right. <source> may be a float, but the value will of course be converted to an integer. shl <destination>[:<index>] <source>[:<index>] Bitwise shift left. cmp <destination>[:<index>] <source>[:<index>] Compare (subtract) <destination> at <index> and <source> at <index>, but don't store it, simply hold on to the result for use with conditional jumps. Neither value necessarily needs to be writable, that is, either side or both sides can be an immediate or a read-only callback. In reality, any value which would be written or passed on to a destination is stored as the result from any of the above operations, for use on a following conditional jump, but it is only 1 value, and it is always replaced on one of these operations, regardless. jump <label> Jump to a label. jumpn <label> Jump to a label if result is not zero. From a cmp operation, this indicates that the two values were different. (cmp a b -> a != b) jumpz <label> Jump to a label if the result is zero. From a cmp operation, this indicates that the two values are equal. (cmp a b -> a == b) jumpl <label> jump to a label if the result is less than zero/negative. From a cmp operation, this indicates that the left value is less than the right value. (cmp a b -> a < b) jumpg <label> Jump to a label if the result is greater than zero/positive. From a cmp operation, this indicates that the left value is greater than the right value. (cmp a b -> a > b) call <procedure> <arguments ...> Call a procedure. All arguments indicated by the procedure must be provided and are passed in as reference to the procedure and may be changed once the procedure returns. PROCEDURES CrustyGame requires of your script that it has 3 procedures, init, event and frame. They can not accept any arguments. init Called once before the execution loop starts. event Called on each event received, at which point callbacks may be used to inspect what the event was and its relevant values. frame Called after all queued events have been processed. Typically rendering should be done here. Each frame starts blank and must be fully redrawn as the surface is double-buffered. Vsync is on by default, but don't expect it to be on, so this procedure may be called irregularly, or the user's display may have a different refresh rate from yours. CALLBACKS The callbacks are the interface between a script and the crustygame engine. They are simply used like a variable, with some caveats addressed above in the description of the move operation. They may have general purposes, relate to data, video, input and hopefully (though not yet) audio. General Callbacks out (W) A single value may be written to it. It will be output to standard output. A character in a string will be output as a byte and an int or float will be output as a numerical value. err (W) Like out but standard error. string_out (W) Write a whole character string to standard out in one go. string_err (W) Like string_out, but standard error. get_ticks (R) Get roughly the number of milliseconds since SDL was initialized. Your only way to track the passage of time. set_running (W) Set to 0 to indicate the program should stop after this frame. Can be reset to non-zero before a frame is finished. get_random (R) Get a random number from the rand() function, seeded at program start with the current UNIX time. If you need something more repeatable or with other special characteristics, you can always implement your own, but this is a quick convenience. set_window_title (W) Sets the window title. Accepts a string. Doesn't need to be null terminated. set_buffer (W) Pass in a buffer to be used by a following callback which needs a buffer. The reference provided is held on to. One can use local variables, but on return the reference will go stale, resulting in undefined data being referenced. This won't result in a program crash as the whole stack is always accessible, but you might get unexpected results if a callback which uses the reference is then called. get_return (R) Read in a value returned by a write callback, where a structure will have been passed in and processed somehow. Graphics Callbacks The way graphics works in CrustyGame is really part of the gimmick of it. It is a fairly flexible, tile and layer based system with some differences to work a bit better with more modern graphics systems. Tilesets must be provided to the engine, then tilemaps must be created and populated with tiles and optional attributes, then layers must be created and assigned tilemaps. Many layers may have the same tilemap. Then layer parameters should be specified and finally indicated to be drawn to the screen. Many of these have helpers in examples/crustygame.inc. gfx_add_tileset (W) Add a tileset from a buffer provided by gfx_set_buffer. This callback takes a buffer of 5 ints. Width of the graphic, in pixels, height of the graphic, in pixels, the row pitch of the graphic, in bytes, the width of each tile, in pixels and the height of each tile in pixels. The graphics data must be 32 bit color in A8R8G8B8 order, with the origin pixel on the top-left, then proceeding row by row. A bmpconvert utility is provided. The GIMP (and possibly others) are able to output BMPs with alpha channel, usable with this program. The result is a super-simplified format that is easy to use by scripts. See examples/crustygame.inc for helper definitions. Tiles are broken out from the texture also starting from the top left corner and proceeding row by row, starting at 0 and increasing from there. As many tiles as can fit the image are indexable. The id will be returned through gfx_get_return. gfx_free_tileset (W) Free the tileset and any resouces. Accepts an id of a tileset as an int. This id will now be free and invalid. The id may be returned again at a later time. gfx_add_tilemap (W) Add a tilemap. Accepts a buffer of 2 ints. The width in tiles of the tilemap and the height in tiles of the tilemap. The id will be returned through gfx_get_return. gfx_free_tilemap (W) Free a tilemap. Accepts an id of a tilemap as an int. Same rules as freed tilesets. gfx_set_tilemap_tileset (W) Assign a tileset to a tilemap. A tileset may be used on many tilemaps. gfx_set_tilemap_map (W) Provide tilemap data to be copied in to the tilemap's own data. Accepts 5 ints. X position of where to start copying to, in tiles. Y position of where to start copying to, in tiles. The row pitch of the whole tilemap data, in tiles. The width of the tilset data to be copied, in tiles and the height of the tileset data to be copied, in tiles. The data is copied from the buffer provided with gfx_set_buffer. Each item takes an int. A 0 may be passed in to the width or height to indicate the full width or full height and a -1 may be passed in for pitch to specify that the width is the same. gfx_set_tilemap_attr_flags (W) Provide an array of tile attribute flags. Arguments are the same as gfx_set_tilemap_map. Each item is an int, with the following flags, defined in examples/crustygame.inc: TILEMAP_HFLIP_MASK Flip the tile horizontally. TILEMAP_VFLIP_MASK Flip the tile vertically. TILEMAP_BFLIP_MASK Flip the tile in both directions. TILEMAP_ROTATE_90 Rotate the tile 90 degrees. Square tiles only. TILEMAP_ROTATE_180 Rotate the tile 180 degrees. TILEMAP_ROTATE_270 Rotate the tile 270 degrees. Square tiles only. gfx_set_tilemap_attr_colormod (W) Provide an array of tile color modulations. Arguments are the same as gfx_set_tilemap_map. Each item is an int, describing a 32 bit color in ARGB format. See the TILEMAP_COLOR macro in examples/crustygame.inc. The tile's colors will be proportionally scaled down by however much the color value is lower than 255, so for example, 127 would halve the value, 63 would quarter the value, etc. gfx_update_tilemap (W) Actually create or update the tilemap based on the tileset, map and attributes provided. A part of the tilemap can be updated without the whole thing being updated. This takes four arguments: The start X position to update in tiles, the start Y position to update in tiles, the width to update in tiles and the height to update in tiles. gfx_add_layer (W) Create a layer and return an id. gfx_free_layer (W) Free a layer id. Same rules as the other free calls. gfx_set_layer_pos (W) Set the position the layer will be drawn at. It accepts an array of 2 ints: The X position in pixels and the Y position in pixels. gfx_set_layer_window (W) Set the window size within the tilemap to draw. Accepts an array of 2 ints, X position in pixels and y position in pixels. Window can be 1,1 to the full size of the tilemap. A 0 may be passed in for an axis reset to full size. gfx_set_layer_scroll_pos (W) Set the scroll position within the tilemap to start drawing. This coincides closely with the layer window size. The restriction is that while it will tile out past the right edge, bottom edge and bottom-right corner, it won't do this infinitely, only once, so the bottom-right corner must be within 1 to 1 less than twice the total length of an axis. gfx_set_layer_scale (W) Set the scale of a layer to be drawn. Accepts 2 floats, the X scale and the Y scale. gfx_set_layer_colormod (W) Sets the color modulation for drawing this layer. May be combined with tilemap attribute colormod, it'll just be stacked. Accepts the same format. gfx_set_layer_blendmode (W) Sets the layer blend mode. Accepts a single integer. Defines are in examples/crustygame.inc, which include: GFX_BLENDMODE_BLEND Alpha blend the layer on top of the image. Colors will be blended between the background and the layer proportional to the alpha value of the pixel, including the colormod. GFX_BLENDMODE_ADD Layer colors will be added to the existing colors behind it, proportional to the layer alpha, including colormod. GFX_BLENDMODE_MOD Like colormod. Color values will be proportionally reduced. Alpha is ignored in this case. GFX_BLENDMODE_MUL I'm not really sure what this is supposed to do, just one of the ones SDL comes with and its description isn't very clear. GFX_BLENDMODE_SUB Like add, just subtracts the layer colors from the layer behind it, proportional to alpha, colormod included. gfx_set_video_mode (W) Set the video mode. Accepts a string formatted as <width>x<height> to change the size of the window. Also accepts fullscreen, to fill the screen at the desktop resolution. This never actually attempts to change desktop display modes, so you'll need to find the width and height after fullscreening and act accordingly. gfx_get_width (R) Get the width of the window in pixels, useful for getting the resolution when fullscreened. gfx_get_height (R) Get the width of the window in pixels. event_get_type (R) Gets the type of an event received. Defines for event types are in examples/crustygame.inc. event_get_time (R) Gets the timestamp of the event, in milliseconds. event_get_button (R) Gets the button an event happened on. Either what key, mouse button or controller button. Also tells which axis or POV hat an axis event happened on. event_get_x (R) Gets the X motion of an action. Gets the direction of a POV hat press. Gets mouse click positions as well as motion positions. When the mouse is locked to the window, it will get a relative mouse movement, if the mouse is not locked, it'll just get the absolute position within the window the corsur moved to. Also gets controller axis motions indicated by the axis in event_get_button. event_get_y (R) Gets the Y motion of an action, like event_get_x but a bit more limited. Doesn't respond to hats or controller axes. event_set_mouse_capture (W) Write a non-zero value to capture the mouse, write a 0 to uncapture the mouse. The user may force uncapture the mouse with CTRL+F10, and the mouse won't be able to be captured again until the user presses CTRL+F10 a second time. savedata_seek (W) Seek to a position in save data storage. savedata_write (W) Write a value in the save data storage. Enough space after the position in the storage needs to be present for the write to complete. A string character is 1 byte, an int is 4 bytes and a float is 8 bytes. savedata_read_char (R) Read a char value from save data storage. savedata_read_int (R) Read an int value from save data storage. savedata_read_float (R) Read a flat value from save data storage.
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