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Correct collation test, to ensure no accidental buffer mixing.

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This commit is contained in:
Thomas Harte
2025-10-03 17:29:45 -04:00
parent 5885bdf0f8
commit 7bb4d052d1
1 changed files with 17 additions and 10 deletions
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27
Machines/Acorn/BBCMicro/BBCMicro.cpp
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@@ -391,8 +391,7 @@ public:
}
void set_control(const uint8_t value) {
crtc_clock_multiplier_ = (value & 0x10) ? 1 : 2;
active_collation_.crtc_clock_multiplier = (value & 0x10) ? 1 : 2;
active_collation_.pixels_per_clock = 1 << ((value >> 2) & 0x03);
active_collation_.is_teletext = value & 0x02;
flash_mask_ = value & 0x01 ? 7 : 0;
@@ -521,7 +520,7 @@ public:
previous_collation_ = active_collation_;
if(!pixel_data_) {
pixel_pointer_ = pixel_data_ = crt_.begin_data(PixelAllocationUnit, 8);
pixel_pointer_ = pixel_data_ = crt_.begin_data(PixelAllocationUnit);
}
if(pixel_data_) {
@@ -539,7 +538,7 @@ public:
pixel_pointer_ += 12;
}
} else {
switch(crtc_clock_multiplier_ * active_collation_.pixels_per_clock) {
switch(active_collation_.crtc_clock_multiplier * active_collation_.pixels_per_clock) {
case 1: shift_pixels<1>(cursor_shifter_ & 7); break;
case 2: shift_pixels<2>(cursor_shifter_ & 7); break;
case 4: shift_pixels<4>(cursor_shifter_ & 7); break;
@@ -552,7 +551,7 @@ public:
}
// Increment cycles since state changed.
cycles_ += crtc_clock_multiplier_ << 3;
cycles_ += active_collation_.crtc_clock_multiplier << 3;
}
/// Sets the destination for output.
@@ -583,12 +582,21 @@ private:
Pixels
};
struct PixelCollation {
int pixels_per_clock;
bool is_teletext;
int crtc_clock_multiplier = 1;
int pixels_per_clock = 4;
bool is_teletext = false;
bool operator !=(const PixelCollation &rhs) {
if(is_teletext && rhs.is_teletext) return false;
return pixels_per_clock != rhs.pixels_per_clock;
// If both are teletext, just inspect the clock multiplier.
if(is_teletext && rhs.is_teletext) {
return crtc_clock_multiplier != rhs.crtc_clock_multiplier;
}
// If one is teletext but the other isn't, that's a sufficient difference.
if(is_teletext != rhs.is_teletext) return true;
// Compare pixel clock rate.
return pixels_per_clock != rhs.pixels_per_clock || crtc_clock_multiplier != rhs.crtc_clock_multiplier;
}
};
@@ -611,7 +619,6 @@ private:
std::bitset<16> flash_flags_;
uint8_t flash_mask_ = 0;
int crtc_clock_multiplier_ = 1;
PixelCollation active_collation_;
uint8_t pixel_shifter_ = 0;