Apple-2-Tools/apple2js
1
0
Fork 0
mirror of https://github.com/whscullin/apple2js.git synced 2024-01-12 14:14:38 +00:00
Code Issues Projects Releases Wiki Activity

Inline look-behind

Browse Source
This commit is contained in:
Will Scullin 2021-07-31 09:41:36 -07:00
parent 0f0388db67
commit 55f4d20056
No known key found for this signature in database
GPG Key ID: 26DCD1042C6638CD
1 changed files with 19 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
js/canvas.ts
View File

@ -615,11 +615,14 @@ export class HiresPage2D implements HiresPage {
// 76543210 76543210 76543210 76543210
// 0000111 1222233 3344445 5556666
// Find the beginning of the current 4 byte/7 pixel window
const mod = col % 2;
const modCol = col - mod;
const baseOff = base - mod;
// 4 consecutive bytes starting at baseOff
// 4 bit look behind for sliding window mode
const bz = this._buffer[0][baseOff - 1];
// 4 bytes for 7 pixels
const b0 = this._buffer[1][baseOff];
const b1 = this._buffer[0][baseOff];
const b2 = this._buffer[1][baseOff + 1];
@ -629,6 +632,7 @@ export class HiresPage2D implements HiresPage {
// Colors normalized
const c = [
((bz & 0x78) >> 3), // -1
((b0 & 0x0f) >> 0), // 0
((b0 & 0x70) >> 4) | ((b1 & 0x01) << 3), // 1
((b1 & 0x1e) >> 1), // 2
@ -636,11 +640,12 @@ export class HiresPage2D implements HiresPage {
((b2 & 0x3c) >> 2), // 4
((b2 & 0x40) >> 6) | ((b3 & 0x07) << 1), // 5
((b3 & 0x78) >> 3), // 6
col < 38 ? ((b4 & 0x0f) >> 0) : 0, // 7
col < 38 ? ((b4 & 0x0f) >> 0) : 0, // 7
];
// High bits
const hb = [
bz & 0x80, // -1
b0 & 0x80, // 0
b0 & 0x80, // 1
b1 & 0x80, // 2
@ -659,19 +664,18 @@ export class HiresPage2D implements HiresPage {
monoColor = whiteCol;
}
// Reassemble 4 bit chunks into 32 bit value
let bits =
c[0] |
(c[1] << 4) |
(c[2] << 8) |
(c[3] << 12) |
(c[4] << 16) |
(c[5] << 20) |
(c[6] << 24) |
(c[7] << 28);
for (let idx = 0; idx < 7; idx++) {
let idx = 1;
// If we're past the first 7 pixels use look-behind
if (modCol) {
idx = 0;
offset -= 16;
}
let bits = c[idx];
for (; idx < 8; idx++) {
const hbs = hb[idx];
bits |= c[idx + 1] << 4;
// Color for mixed and RGB mode
const dcolor = _colors[r4[bits & 0xf]];
for (let jdx = 0; jdx < 4; jdx++, offset += 4) {
@ -686,26 +690,15 @@ export class HiresPage2D implements HiresPage {
} else if (this.rgbDHRMode) {
this._drawHalfPixel(data, offset, dcolor);
} else { // sliding window
// use 4 bit window to select color
let slide = bits & 0x0f;
// adjust for window position
slide = ((slide >> (4 -jdx)) | (slide << jdx)) & 0x0f;
this._drawHalfPixel(data, offset, _colors[r4[slide]]);
}
bits >>= 1;
}
}
// If we're doing sliding window and updated the first byte refresh the prior 7 pixels
// TODO(whscullin) - only refresh the last pixel
const slidingMode = !monoColor && !this.mixedDHRMode && !this.rgbDHRMode;
if (!this._refreshing && bank === 1 && col === modCol && slidingMode) {
this._refreshing = true;
const refreshAddr = addr - 1;
const refreshOff = refreshAddr >> 8;
const refreshPage = refreshAddr & 0xff;
const refreshVal = this._read(refreshOff, refreshPage, 0);
this._write(refreshOff, refreshPage, refreshVal, 0);
this._refreshing = false;
}
} else {
val = this._buffer[0][base];
const hbs = val & 0x80;