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Makes a first attempt at displaying text mode.

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This commit is contained in:
Thomas Harte 2017-11-30 21:35:26 -05:00
parent 5da9cb2957
commit 9c8158753e
2 changed files with 72 additions and 18 deletions
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86
Components/9918/9918.cpp
View File

@ -87,8 +87,36 @@ void TMS9918::run_for(const HalfCycles cycles) {
if(row_ < 192) {
// Do memory accesses.
switch(next_screen_mode_) {
default: // TODO: other graphics mode; this is graphics 1.
switch(line_mode_) {
case LineMode::Text:
while(access_pointer_ < (column_ >> 1)) {
if(access_pointer_ < 29) {
access_pointer_ = std::min(29, column_ >> 1);
}
if(access_pointer_ >= 29) {
int end = std::min(149, column_);
const int row_base = pattern_name_address_ + (row_ >> 3) * 40;
while(access_pointer_ < end) {
// Even worse than below; work to do.
int character_column = (access_pointer_ - 29) / 3;
switch(access_pointer_%3) {
case 2: pattern_name_ = ram_[row_base + character_column]; break;
case 1: break;
case 0:
colour_buffer_[character_column] = text_background_colour_;
pattern_buffer_[character_column] = ram_[pattern_generator_table_address_ + (pattern_name_ << 3) + (row_ & 7)];
break;
}
access_pointer_++;
}
}
if(access_pointer_ >= 149) {
access_pointer_ = column_ >> 1;
}
}
break;
case LineMode::Character:
while(access_pointer_ < (column_ >> 1)) {
if(access_pointer_ < 26) {
access_pointer_ = std::min(26, column_ >> 1);
@ -97,12 +125,12 @@ void TMS9918::run_for(const HalfCycles cycles) {
int end = std::min(154, column_);
// TODO: optimise this mess.
const int row_base = ((row_ << 2)&~31);
const int row_base = pattern_name_address_ + ((row_ << 2)&~31);
while(access_pointer_ < end) {
int character_column = ((access_pointer_ - 26) >> 2);
switch(access_pointer_&3) {
case 0:
pattern_name_ = ram_[pattern_name_address_ + row_base + character_column];
pattern_name_ = ram_[row_base + character_column];
break;
case 1: break; // TODO: sprites / CPU access.
case 2:
@ -141,23 +169,42 @@ void TMS9918::run_for(const HalfCycles cycles) {
}
if(output_column_ >= first_pixel_column_) {
int pixels_end = std::min(first_right_border_column_, column_);
if(output_column_ < pixels_end) {
while(output_column_ < pixels_end) {
int base = (output_column_ - first_pixel_column_);
int address = base >> 3;
uint8_t colour = colour_buffer_[address];
uint8_t pattern = pattern_buffer_[address];
pattern >>= ((base&7)^7);
switch(line_mode_) {
case LineMode::Text:
while(output_column_ < pixels_end) {
int base = (output_column_ - first_pixel_column_);
int address = base / 6;
uint8_t colour = colour_buffer_[address];
uint8_t pattern = pattern_buffer_[address];
pattern >>= ((base % 6)^7);
*pixel_target_ = (pattern&1) ? palette[colour >> 4] : palette[colour & 15];
pixel_target_ ++;
output_column_ ++;
}
*pixel_target_ = (pattern&1) ? palette[colour >> 4] : palette[colour & 15];
pixel_target_ ++;
output_column_ ++;
}
break;
if(output_column_ == first_right_border_column_) {
crt_->output_data(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_), 1);
case LineMode::Character:
while(output_column_ < pixels_end) {
int base = (output_column_ - first_pixel_column_);
int address = base >> 3;
uint8_t colour = colour_buffer_[address];
uint8_t pattern = pattern_buffer_[address];
pattern >>= ((base&7)^7);
*pixel_target_ = (pattern&1) ? palette[colour >> 4] : palette[colour & 15];
pixel_target_ ++;
output_column_ ++;
}
break;
}
}
if(output_column_ == first_right_border_column_) {
crt_->output_data(static_cast<unsigned int>(first_right_border_column_ - first_pixel_column_), 1);
}
}
if(column_ >= first_pixel_column_) {
output_border(column_ - output_column_);
@ -188,7 +235,11 @@ void TMS9918::run_for(const HalfCycles cycles) {
screen_mode_ = next_screen_mode_;
switch(screen_mode_) {
// TODO: text mdoe.
case 2:
line_mode_ = LineMode::Text;
first_pixel_column_ = 69;
first_right_border_column_ = 309;
break;
default:
line_mode_ = LineMode::Character;
first_pixel_column_ = 63;
@ -265,6 +316,7 @@ void TMS9918::set_register(int address, uint8_t value) {
break;
case 7:
text_background_colour_ = low_write_;
text_colour_ = low_write_ >> 4;
background_colour_ = low_write_ & 0xf;
break;

4
Components/9918/9918.hpp
View File

@ -71,8 +71,10 @@ class TMS9918 {
uint16_t pattern_generator_table_address_ = 0;
uint16_t sprite_attribute_table_address_ = 0;
uint16_t sprite_generator_table_address_ = 0;
uint8_t text_colour_ = 0;
uint8_t background_colour_ = 0;
uint8_t text_background_colour_ = 0;
HalfCycles half_cycles_into_frame_;
int column_ = 0, row_ = 0, output_column_ = 0;
@ -93,7 +95,7 @@ class TMS9918 {
int first_pixel_column_, first_right_border_column_;
uint8_t pattern_buffer_[40];
uint8_t colour_buffer_[32];
uint8_t colour_buffer_[40];
int access_pointer_ = 0;
uint8_t pattern_name_ = 0;
};