open https://gitlab.synchro.net/main/sbbs/-/issues/1007

If you use Frame.js's .putmsg() to write text in a color (say blue-on-black), then OVERWRITE that text with identical text in a different color (say red-on-black), it works as expected.

But if instead you were to overwrite with BLACK-on-black, it does NOT work. The frame keeps the previous foreground attribute (blue) instead of changing to black.

In contrast, console.putmsg() does NOT have this problem. It handles black-on-black just fine.

I presume there is a logic problem in Frame.prototype.putmsg(), but I haven't been able to figure it out.

Here's a short test case script:

```
load("sbbsdefs.js");
load("frame.js");

// COLOR CODES
var lowRed = '\1N\1R\10';
var lowBlue = '\1N\1B\10';
var lowWhite = '\1N\1W\10';
var highCyan = '\1H\1C\10';
var lowBlack = '\1N\1K\10';
var highBlack = '\1H\1K\10';

console.clear();

// PLAIN CONSOLE VERSION
console.gotoxy(1,1);
console.putmsg(lowWhite + 'PLAIN CONSOLE VERSION');
mswait(4000);
console.gotoxy(1,1);
console.putmsg(lowBlue + 'TEST1 TEST1' + highBlack + ' ... should say TEST1 TEST1 in low blue on black ');
mswait(4000);
console.gotoxy(1,1);
console.putmsg(lowBlack + 'TEST2 TEST2' + highBlack + ' ... should say TEST2 TEST2 in black on black ');
mswait(4000);
console.gotoxy(1,1);
console.putmsg(highCyan + 'TEST3 TEST3' + highBlack + ' ... should say TEST3 TEST3 in high cyan on black ');
mswait(4000);

// FRAME VERSION
testFrame = new Frame(1, 1, 80, 24, BG_BLACK);
testFrame.open();
testFrame.draw();
testFrame.gotoxy(1,1);
testFrame.putmsg(lowWhite + 'FRAME.JS VERSION');
testFrame.cycle();
mswait(4000);
testFrame.gotoxy(1,1);
testFrame.putmsg(lowBlue + 'TEST1 TEST1' + highBlack + ' ... should say TEST1 TEST1 in low blue on black ');
testFrame.cycle();
mswait(4000);
testFrame.gotoxy(1,1);
testFrame.putmsg(lowBlack + 'TEST2 TEST2' + highBlack + ' ... should say TEST2 TEST2 in black on black ');
testFrame.cycle();
mswait(4000);
testFrame.gotoxy(1,1);
testFrame.putmsg(highCyan + 'TEST3 TEST3' + highBlack + ' ... should say TEST3 TEST3 in high cyan on black ');
testFrame.cycle();
mswait(4000);
```
--- SBBSecho 3.31-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)

https://gitlab.synchro.net/main/sbbs/-/issues/1007#note_7872

The problem appears to be line 391 in frame.js...

```javascript
if(attr)
this.__properties__.data[py][px].attr = attr;
```

Since (dark) black on black has a value of zero, it doesn't actually get set.

This change was apparently made in 2011 with commit 72488196a51
--- SBBSecho 3.31-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)

https://gitlab.synchro.net/main/sbbs/-/issues/1007#note_7874

A simple workaround would be to use *blinking* black on black. :grin:
--- SBBSecho 3.31-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)

https://gitlab.synchro.net/main/sbbs/-/issues/1007#note_7875

A better check might be `if(attr !== undefined)`? Or maybe a comparison with the existing attr to see if they're different?

```
if(attr !== undefined && properties.data[x + position.offset.x][y + position.offset.y].attr != attr)
properties.data[x + position.offset.x][y + position.offset.y].attr = attr;
```
?
--- SBBSecho 3.31-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)

https://gitlab.synchro.net/main/sbbs/-/issues/1007#note_7876

Actually, on second thought, that's probably a bad idea -- `undefined` is used for transparency.

I should probably try some tests.
--- SBBSecho 3.31-Linux
* Origin: Vertrauen - [vert/cvs/bbs].synchro.net (1:103/705)