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Corrects buffer overrun when the horizontal scroll lock is on.

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This commit is contained in:
Thomas Harte 2018-10-08 23:06:22 -04:00
parent 7a74fe2ff7
commit 748366c70e
1 changed files with 6 additions and 5 deletions
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11
Components/9918/9918.cpp
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@ -720,6 +720,7 @@ void Base::draw_sms(int start, int end) {
Add extra border for any pixels that fall before the fine scroll.
*/
int tile_start = start, tile_end = end;
int tile_offset = start;
if(row_ >= 16 || !master_system_.horizontal_scroll_lock) {
for(int c = start; c < (master_system_.horizontal_scroll & 7); ++c) {
colour_buffer[c] = 16 + background_colour_;
@ -728,6 +729,7 @@ void Base::draw_sms(int start, int end) {
// Remove the border area from that to which tiles will be drawn.
tile_start = std::max(start - (master_system_.horizontal_scroll & 7), 0);
tile_end = std::max(end - (master_system_.horizontal_scroll & 7), 0);
tile_offset += master_system_.horizontal_scroll & 7;
}
@ -740,7 +742,6 @@ void Base::draw_sms(int start, int end) {
priority over sprites.
*/
if(tile_start < end) {
int offset = (master_system_.horizontal_scroll & 7) + tile_start;
const int shift = tile_start & 7;
int byte_column = tile_start >> 3;
int pixels_left = tile_end - tile_start;
@ -757,24 +758,24 @@ void Base::draw_sms(int start, int end) {
const int palette_offset = (master_system_.names[byte_column].flags&0x18) << 1;
if(master_system_.names[byte_column].flags&2) {
for(int c = 0; c < length; ++c) {
colour_buffer[offset] =
colour_buffer[tile_offset] =
((pattern_index[3] & 0x01) << 3) |
((pattern_index[2] & 0x01) << 2) |
((pattern_index[1] & 0x01) << 1) |
((pattern_index[0] & 0x01) << 0) |
palette_offset;
++offset;
++tile_offset;
pattern >>= 1;
}
} else {
for(int c = 0; c < length; ++c) {
colour_buffer[offset] =
colour_buffer[tile_offset] =
((pattern_index[3] & 0x80) >> 4) |
((pattern_index[2] & 0x80) >> 5) |
((pattern_index[1] & 0x80) >> 6) |
((pattern_index[0] & 0x80) >> 7) |
palette_offset;
++offset;
++tile_offset;
pattern <<= 1;
}
}