75 lines
1.7 KiB
Go
75 lines
1.7 KiB
Go
package izapple2
|
|
|
|
import (
|
|
"errors"
|
|
|
|
"github.com/ivanizag/izapple2/storage"
|
|
)
|
|
|
|
/*
|
|
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
|
|
}
|
|
|
|
type charColumnMap func(column int) int
|
|
|
|
func charGenColumnsMap2Plus(column int) int {
|
|
return 6 - column
|
|
}
|
|
|
|
func charGenColumnsMap2e(column int) int {
|
|
return column
|
|
}
|
|
|
|
const (
|
|
charGenPageSize = 2048
|
|
)
|
|
|
|
// NewCharacterGenerator instantiates a new Character Generator with the rom on the file given
|
|
func newCharacterGenerator(filename string, order charColumnMap) (*CharacterGenerator, error) {
|
|
var cg CharacterGenerator
|
|
err := cg.load(filename)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
cg.columnMap = order
|
|
return &cg, nil
|
|
}
|
|
|
|
func (cg *CharacterGenerator) load(filename string) error {
|
|
bytes, _, err := storage.LoadResource(filename)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
size := len(bytes)
|
|
if size < charGenPageSize {
|
|
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) / charGenPageSize
|
|
cg.page = page % pages
|
|
}
|
|
|
|
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*charGenPageSize]
|
|
bit := cg.columnMap(column)
|
|
value := bits >> uint(bit) & 1
|
|
return value == 1
|
|
}
|