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Default to CGA40 if starting a new composite PC.

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This commit is contained in:
Thomas Harte 2023-12-07 10:14:06 -05:00
parent 0f22ee5de4
commit ad78a03300
1 changed files with 26 additions and 0 deletions
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26
Machines/PCCompatible/PCCompatible.cpp
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@ -550,6 +550,25 @@ class i8255PortHandler : public Intel::i8255::PortHandler {
if(drive_count) low_switches_ |= 0xb0001;
}
/// Supplies a hint about the user's display choice. If the high switches haven't been read yet and this is a CGA device,
/// this hint will be used to select between 40- and 80-column default display.
void hint_is_composite(bool composite) {
if(high_switches_observed_) {
return;
}
switch(high_switches_ & 3) {
// Do nothing if a non-CGA card is in use.
case 0b00: case 0b11:
break;
default:
high_switches_ &= ~0b11;
high_switches_ |= composite ? 0b01 : 0b10;
break;
}
}
void set_value(int port, uint8_t value) {
switch(port) {
case 1:
@ -572,6 +591,7 @@ class i8255PortHandler : public Intel::i8255::PortHandler {
uint8_t get_value(int port) {
switch(port) {
case 0:
high_switches_observed_ = true;
return enable_keyboard_ ? keyboard_.read() : uint8_t((high_switches_ << 4) | low_switches_);
// Guesses that switches is high and low combined as below.
@ -581,6 +601,7 @@ class i8255PortHandler : public Intel::i8255::PortHandler {
// b5: timer 2 output; [TODO]
// b4: cassette data input; [TODO]
// b3...b0: whichever of the high and low switches is selected.
high_switches_observed_ |= use_high_switches_;
return
use_high_switches_ ? high_switches_ : low_switches_;
}
@ -588,6 +609,7 @@ class i8255PortHandler : public Intel::i8255::PortHandler {
};
private:
bool high_switches_observed_ = false;
uint8_t high_switches_ = 0;
uint8_t low_switches_ = 0;
@ -1087,6 +1109,10 @@ class ConcreteMachine:
void set_display_type(Outputs::Display::DisplayType display_type) override {
video_.set_display_type(display_type);
ppi_handler_.hint_is_composite(
(display_type == Outputs::Display::DisplayType::CompositeColour) ||
(display_type == Outputs::Display::DisplayType::CompositeMonochrome)
);
}
Outputs::Display::DisplayType get_display_type() const override {