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Tidyup: vga comments, and panning update code

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Ernest Wong 2018-01-16 18:06:35 +13:00 committed by Fabian
parent eaa90a8c89
commit 25da2e80ac
1 changed files with 7 additions and 8 deletions
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15
src/vga.js
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@ -721,8 +721,6 @@ VGAScreen.prototype.vga_memory_write_graphical = function(addr, value)
var setreset_dword = this.apply_expand(this.planar_setreset);
var setreset_enable_dword = this.apply_expand(this.planar_setreset_enable);
// TODO: assert register consistency
// Write modes - see http://www.osdever.net/FreeVGA/vga/graphreg.htm#05
switch(write_mode)
{
@ -1265,12 +1263,11 @@ VGAScreen.prototype.update_vga_size = function()
{
this.svga_width = horizontal_characters << 3;
// Offset is the number of words or dwords (depending on clocking mode)
// Offset is half the number of bytes/words/dwords (depending on clocking mode)
// of display memory that each logical line occupies.
// However, the number of pixels latched, regardless of addressing mode,
// is always 8 pixels per character clock (except for 256 color, in which
// should always 8 pixels per character clock (except for 8 bit PEL width, in which
// case 4 pixels).
// TODO: verify this calculation
this.virtual_width = this.offset_register << 4;
// Pixel Width / PEL Width / Clock Select
@ -1340,9 +1337,11 @@ VGAScreen.prototype.update_vga_panning = function()
var start_addr = this.start_address_latched;
// TODO: merge this with other logic?
var pixel_panning = this.horizontal_panning;
if(this.attribute_mode & 0x40) pixel_panning >>>= 1;
if(this.attribute_mode & 0x40)
{
pixel_panning >>>= 1;
}
var byte_panning = this.preset_row_scan >> 5 & 0x3;
var pixel_addr_start = this.vga_addr_to_pixel(start_addr + byte_panning);
@ -1352,7 +1351,6 @@ VGAScreen.prototype.update_vga_panning = function()
start_buffer_col += pixel_panning;
var split_screen_row = this.scan_line_to_screen_row(1 + this.line_compare);
split_screen_row = Math.min(split_screen_row, this.svga_height);
var split_buffer_height = this.svga_height - split_screen_row;
@ -1374,6 +1372,7 @@ VGAScreen.prototype.update_vga_panning = function()
var start_split_col = 0;
if(!(this.attribute_mode & 0x20))
{
// Pixel panning mode. Allow panning for the lower split screen
start_split_col = this.vga_addr_to_pixel(byte_panning) + pixel_panning;
}