package izapple2 import ( "errors" ) /* See: https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Companies/Apple/Documentation/Apple%20Technical%20Information%20Library/a2til041.txt */ // CharacterGenerator represents the ROM wth the characters bitmaps type CharacterGenerator struct { data []uint8 columnMap charColumnMap page int pageSize int } type charColumnMap func(column int) int func charGenColumnsMap2Plus(column int) int { return 6 - column } func charGenColumnsMap2e(column int) int { return column } const ( charGenPageSize2Plus = 2048 charGenPageSize2E = 2048 * 2 ) // NewCharacterGenerator instantiates a new Character Generator with the rom on the file given func newCharacterGenerator(filename string, order charColumnMap, isApple2e bool) (*CharacterGenerator, error) { var cg CharacterGenerator cg.columnMap = order cg.pageSize = charGenPageSize2Plus if isApple2e { cg.pageSize = charGenPageSize2E } err := cg.load(filename) if err != nil { return nil, err } return &cg, nil } func (cg *CharacterGenerator) load(filename string) error { bytes, _, err := LoadResource(filename) if err != nil { return err } size := len(bytes) if size < cg.pageSize { return errors.New("character ROM size not supported") } cg.data = bytes return nil } func (cg *CharacterGenerator) setPage(page int) { // Some clones had a switch to change codepage with extra characters pages := len(cg.data) / cg.pageSize cg.page = page % pages } func (cg *CharacterGenerator) getPage() int { return cg.page } func (cg *CharacterGenerator) nextPage() { cg.setPage(cg.page + 1) } func (cg *CharacterGenerator) getPixel(char uint8, row int, column int) bool { bits := cg.data[int(char)*8+row+cg.page*cg.pageSize] bit := cg.columnMap(column) value := bits >> uint(bit) & 1 return value == 1 }