From cd615ce93936c5e322c0fda6680536767537e5b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Wed, 9 Aug 2023 14:49:04 +0100
Subject: [PATCH] fix: issue related to the `update_tile()` method In restoring
the VRAM
---
src/mmu.rs | 2 +-
src/ppu.rs | 24 +++++++++++++++++++-----
2 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/src/mmu.rs b/src/mmu.rs
index 68d38cd3..c1af90d9 100644
--- a/src/mmu.rs
+++ b/src/mmu.rs
@@ -250,7 +250,7 @@ impl Mmu {
// @TODO: Implement DMA transfer in a better way
// only runs the DMA transfer if the system is in CGB mode
- // this avoid issues when writing to DMG unmapped registers
+ // this avoids issues when writing to DMG unmapped registers
// that would otherwise cause the system to crash
if self.mode == GameBoyMode::Cgb {
let data = self.read_many(self.dma.source(), self.dma.length());
diff --git a/src/ppu.rs b/src/ppu.rs
index b5ca06c4..fb6ec67f 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -1175,22 +1175,36 @@ impl Ppu {
/// to the VRAM values, this should be called whenever the VRAM
/// is replaced.
pub fn update_vram(&mut self) {
+ // "saves" the old values of the VRAM bank and offset
+ // as they are going to be needed later, this is required
+ // as we're going to trick the PPU into switching banks
+ // over the update of the calculated values for the new VRAM,
+ // essentially required for the `update_tile()` method
+ let (vram_bank_old, vram_offset_old) = (self.vram_bank, self.vram_offset);
+
+ // determines the number of VRAM banks available according
+ // to the running Game Boy running mode (CGB vs DMG)
let vram_banks = if self.gb_mode == GameBoyMode::Cgb {
- 2u16
+ 2u8
} else {
- 1u16
+ 1u8
};
+
for vram_bank in 0..vram_banks {
- let vram_offset = vram_bank * 0x2000;
+ self.vram_bank = vram_bank;
+ self.vram_offset = self.vram_bank as u16 * 0x2000;
for addr in 0x8000..=0x9fff {
- let value = self.vram[(vram_offset + (addr & 0x1fff)) as usize];
+ let value = self.vram[(self.vram_offset + (addr & 0x1fff)) as usize];
if addr < 0x9800 {
self.update_tile(addr, value);
- } else if vram_bank == 0x1 {
+ } else if self.vram_bank == 0x1 {
self.update_bg_map_attrs(addr, value);
}
}
}
+
+ // restores the "old" values for VRAM bank and offset
+ (self.vram_bank, self.vram_offset) = (vram_bank_old, vram_offset_old);
}
/// Updates the tile structure with the value that has
--
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