76 lines
1.7 KiB
Go
76 lines
1.7 KiB
Go
package apple2
|
|
|
|
import (
|
|
"image"
|
|
"image/color"
|
|
"time"
|
|
)
|
|
|
|
const (
|
|
charWidth = 7
|
|
charHeight = 8
|
|
textColumns = 40
|
|
textLines = 24
|
|
textLinesMix = 4
|
|
textPage1Address = uint16(0x0400)
|
|
textPage2Address = uint16(0x0800)
|
|
)
|
|
|
|
func getTextCharOffset(col int, line int) uint16 {
|
|
|
|
// See "Understanding the Apple II", page 5-10
|
|
// http://www.applelogic.org/files/UNDERSTANDINGTHEAII.pdf
|
|
section := line / 8 // Top, middle and bottom
|
|
eigth := line % 8
|
|
return uint16(section*40 + eigth*0x80 + col)
|
|
}
|
|
|
|
func getTextChar(a *Apple2, col int, line int, page int) uint8 {
|
|
address := textPage1Address
|
|
if page == 1 {
|
|
address = textPage2Address
|
|
}
|
|
address += getTextCharOffset(col, line)
|
|
return a.mmu.physicalMainRAM.subRange(address, address+1)[0]
|
|
}
|
|
|
|
func snapshotTextMode(a *Apple2, page int, mixMode bool, light color.Color) *image.RGBA {
|
|
// Flash mode is 2Hz
|
|
isFlashedFrame := time.Now().Nanosecond() > (1 * 1000 * 1000 * 1000 / 2)
|
|
|
|
lineStart := 0
|
|
if mixMode {
|
|
lineStart = textLines - textLinesMix
|
|
}
|
|
|
|
width := textColumns * charWidth
|
|
height := (textLines - lineStart) * charHeight
|
|
size := image.Rect(0, 0, width, height)
|
|
img := image.NewRGBA(size)
|
|
|
|
for x := 0; x < width; x++ {
|
|
for y := 0; y < height; y++ {
|
|
line := y/charHeight + lineStart
|
|
col := x / charWidth
|
|
rowInChar := y % charHeight
|
|
colInChar := x % charWidth
|
|
char := getTextChar(a, col, line, page)
|
|
topBits := char >> 6
|
|
isInverse := topBits == 0
|
|
isFlash := topBits == 1
|
|
|
|
pixel := a.cg.getPixel(char, rowInChar, colInChar)
|
|
pixel = pixel != (isInverse || (isFlash && isFlashedFrame))
|
|
var colour color.Color
|
|
if pixel {
|
|
colour = light
|
|
} else {
|
|
colour = color.Black
|
|
}
|
|
img.Set(x, y, colour)
|
|
}
|
|
}
|
|
|
|
return img
|
|
}
|