From bfa167fcdfb2a485223b0a901a7ea6b5d01d03d9 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 26 Feb 2023 13:42:59 -0500
Subject: [PATCH] Make attempt at the TP background-colour bit.

---
 Components/9918/Implementation/9918.cpp     | 8 ++++++++
 Components/9918/Implementation/9918Base.hpp | 2 +-
 Components/9918/Implementation/Storage.hpp  | 3 +++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Components/9918/Implementation/9918.cpp b/Components/9918/Implementation/9918.cpp
index 87456ed79..ff8724d0a 100644
--- a/Components/9918/Implementation/9918.cpp
+++ b/Components/9918/Implementation/9918.cpp
@@ -773,9 +773,14 @@ void Base<personality>::commit_register(int reg, uint8_t value) {
 				LOG("Screen mode: " << int(current_screen_mode<true>()));
 			break;
 
+			case 7:
+				Storage<personality>::background_palette_[0] = Storage<personality>::palette_[background_colour_];
+			break;
+
 			case 8:
 				LOG("TODO: Yamaha VRAM organisation, sprite disable, etc; " << PADHEX(2) << +value);
 				Storage<personality>::sprites_enabled_ = !(value & 0x02);
+				Storage<personality>::solid_background_ = value & 0x20;
 				// b7: "1 = input on colour bus, enable mouse; 1 = output on colour bus, disable mouse" [documentation clearly in error]
 				// b6: 1 = enable light pen
 				// b5: sets the colour of code 0 to the colour of the palette (???)
@@ -1013,6 +1018,9 @@ void Base<personality>::write_palette(uint8_t value) {
 		const uint8_t b = (Storage<personality>::new_colour_ & 7) * 255 / 7;
 
 		Storage<personality>::palette_[Storage<personality>::palette_entry_ & 0xf] = palette_pack(r, g, b);
+		Storage<personality>::background_palette_[Storage<personality>::palette_entry_ & 0xf] = palette_pack(r, g, b);
+		Storage<personality>::background_palette_[0] = Storage<personality>::palette_[background_colour_];
+
 		++Storage<personality>::palette_entry_;
 	}
 }
diff --git a/Components/9918/Implementation/9918Base.hpp b/Components/9918/Implementation/9918Base.hpp
index 024bf77a5..9e7a95d09 100644
--- a/Components/9918/Implementation/9918Base.hpp
+++ b/Components/9918/Implementation/9918Base.hpp
@@ -75,7 +75,7 @@ template <Personality personality> struct Base: public Storage<personality> {
 	};
 	const std::array<uint32_t, 16> &palette() {
 		if constexpr (is_yamaha_vdp(personality)) {
-			return Storage<personality>::palette_;
+			return Storage<personality>::solid_background_ ? Storage<personality>::palette_ : Storage<personality>::background_palette_;
 		}
 		return default_palette;
 	}
diff --git a/Components/9918/Implementation/Storage.hpp b/Components/9918/Implementation/Storage.hpp
index 80ebb0cf7..f83d8acac 100644
--- a/Components/9918/Implementation/Storage.hpp
+++ b/Components/9918/Implementation/Storage.hpp
@@ -40,6 +40,9 @@ template <Personality personality> struct Storage<personality, std::enable_if_t<
 	bool increment_indirect_register_ = false;
 
 	std::array<uint32_t, 16> palette_{};
+	std::array<uint32_t, 16> background_palette_{};
+	bool solid_background_ = true;
+
 	uint8_t new_colour_ = 0;
 	uint8_t palette_entry_ = 0;
 	bool palette_write_phase_ = false;