GBA: Regrettably add VBA bug compat mode

CHANGES

@@ -7,6 +7,7 @@ Features:
  - Frame viewer support for Game Boy
  - Mute option in homebrew ports
  - Status indicators for fast-forward and mute in homebrew ports
+ - VBA bug compatibility mode for ROM hacks that don't work on real hardware
  - Read-only support for MBC6 flash memory
  - New unlicensed GB mappers: Pokémon Jade/Diamond, BBD, and Hitek
  - Stack tracing tools in ARM debugger (by ahigerd)

include/mgba/internal/gba/gba.h

@@ -116,6 +116,7 @@ struct GBA {
 	int32_t cachedRegisters[16];
 	bool taintedRegisters[16];
 
+	bool vbaBugCompat;
 	bool hardCrash;
 	bool allowOpposingDirections;
 

include/mgba/internal/gba/overrides.h

@@ -20,6 +20,7 @@ struct GBACartridgeOverride {
 	int hardware;
 	uint32_t idleLoop;
 	bool mirroring;
+	bool vbaBugCompat;
 };
 
 struct Configuration;

src/gba/gba.c

@@ -108,6 +108,7 @@ static void GBAInit(void* cpu, struct mCPUComponent* component) {
 	gba->idleOptimization = IDLE_LOOP_REMOVE;
 	gba->idleLoop = IDLE_LOOP_NONE;
 
+	gba->vbaBugCompat = false;
 	gba->hardCrash = true;
 	gba->allowOpposingDirections = true;
 

src/gba/hardware.c

@@ -99,8 +99,12 @@ void GBAHardwareGPIOWrite(struct GBACartridgeHardware* hw, uint32_t address, uin
 	}
 	switch (address) {
 	case GPIO_REG_DATA:
-		hw->pinState &= ~hw->direction;
+		if (!hw->p->vbaBugCompat) {
-		hw->pinState |= value & hw->direction;
+			hw->pinState &= ~hw->direction;
+			hw->pinState |= value & hw->direction;
+		} else {
+			hw->pinState = value;
+		}
 		_readPins(hw);
 		break;
 	case GPIO_REG_DIRECTION:

src/gba/overrides.c

@@ -207,6 +207,7 @@ bool GBAOverrideFind(const struct Configuration* config, struct GBACartridgeOver
 	override->hardware = HW_NONE;
 	override->idleLoop = IDLE_LOOP_NONE;
 	override->mirroring = false;
+	override->vbaBugCompat = false;
 	bool found = false;
 
 	int i;
@@ -320,6 +321,8 @@ void GBAOverrideApply(struct GBA* gba, const struct GBACartridgeOverride* overri
 		GBASavedataForceType(&gba->memory.savedata, override->savetype);
 	}
 
+	gba->vbaBugCompat = override->vbaBugCompat;
+
 	if (override->hardware != HW_NO_OVERRIDE) {
 		GBAHardwareClear(&gba->memory.hw);
 
@@ -376,6 +379,7 @@ void GBAOverrideApplyDefaults(struct GBA* gba, const struct Configuration* overr
 			// Enable FLASH1M and RTC on Pokémon FireRed ROM hacks
 			override.savetype = SAVEDATA_FLASH1M;
 			override.hardware = HW_RTC;
+			override.vbaBugCompat = true;
 			GBAOverrideApply(gba, &override);
 		} else if (GBAOverrideFind(overrides, &override)) {
 			GBAOverrideApply(gba, &override);

src/platform/qt/OverrideView.cpp

@@ -142,6 +142,7 @@ void OverrideView::updateOverrides() {
 		gba->override.hardware = HW_NO_OVERRIDE;
 		gba->override.idleLoop = IDLE_LOOP_NONE;
 		gba->override.mirroring = false;
+		gba->override.vbaBugCompat = false;
 
 		if (!m_ui.hwAutodetect->isChecked()) {
 			gba->override.hardware = HW_NONE;
@@ -164,6 +165,9 @@ void OverrideView::updateOverrides() {
 		if (m_ui.hwGBPlayer->isChecked()) {
 			gba->override.hardware |= HW_GB_PLAYER_DETECTION;
 		}
+		if (m_ui.vbaBugCompat->isChecked()) {
+			gba->override.vbaBugCompat = true;
+		}
 
 		bool ok;
 		uint32_t parsedIdleLoop = m_ui.idleLoop->text().toInt(&ok, 16);
@@ -219,6 +223,7 @@ void OverrideView::gameStarted() {
 		m_ui.hwTilt->setChecked(gba->memory.hw.devices & HW_TILT);
 		m_ui.hwRumble->setChecked(gba->memory.hw.devices & HW_RUMBLE);
 		m_ui.hwGBPlayer->setChecked(gba->memory.hw.devices & HW_GB_PLAYER_DETECTION);
+		m_ui.vbaBugCompat->setChecked(gba->vbaBugCompat);
 
 		if (gba->idleLoop != IDLE_LOOP_NONE) {
 			m_ui.idleLoop->setText(QString::number(gba->idleLoop, 16));

src/platform/qt/OverrideView.ui

@@ -175,41 +175,18 @@
            </widget>
           </item>
           <item>
-           <layout class="QHBoxLayout" name="horizontalLayout_2">
+           <widget class="QCheckBox" name="hwGBPlayer">
-            <item>
+            <property name="text">
-             <spacer name="horizontalSpacer">
+             <string>Game Boy Player features</string>
-              <property name="orientation">
+            </property>
-               <enum>Qt::Horizontal</enum>
+           </widget>
-              </property>
+          </item>
-              <property name="sizeHint" stdset="0">
+          <item>
-               <size>
+           <widget class="QCheckBox" name="vbaBugCompat">
-                <width>0</width>
+            <property name="text">
-                <height>0</height>
+             <string>VBA bug compatibility mode</string>
-               </size>
+            </property>
-              </property>
+           </widget>
-             </spacer>
-            </item>
-            <item>
-             <widget class="QCheckBox" name="hwGBPlayer">
-              <property name="text">
-               <string>Game Boy Player features</string>
-              </property>
-             </widget>
-            </item>
-            <item>
-             <spacer name="horizontalSpacer_3">
-              <property name="orientation">
-               <enum>Qt::Horizontal</enum>
-              </property>
-              <property name="sizeHint" stdset="0">
-               <size>
-                <width>0</width>
-                <height>0</height>
-               </size>
-              </property>
-             </spacer>
-            </item>
-           </layout>
           </item>
          </layout>
         </widget>