pokeemerald/docs/bugs_and_glitches.md

# Bugs and Glitches

These are known bugs and glitches in the original Pokémon Emerald game: code that clearly does not work as intended, or that only works in limited circumstances but has the possibility to fail or crash. Defining the `BUGFIX` preprocessor variable will fix some of these automatically.

Fixes are written in the `diff` format. If you've used Git before, this should look familiar:

```diff
 this is some code
-delete red - lines
+add green + lines
```

## Contents

- [RNG does not get seeded](#rng-does-not-get-seeded)
- [Scrolling through items in the bag causes the image to flicker](#scrolling-through-items-in-the-bag-causes-the-image-to-flicker)


## RNG does not get seeded

**Fix:** Add the following function to [src/main.c](https://github.com/pret/pokeemerald/blob/master/src/main.c):
```diff
+static void SeedRngWithRtc(void)
+{
+	u32 seed = RtcGetMinuteCount();
+	seed = (seed >> 16) ^ (seed & 0xFFFF);
+	SeedRng(seed);
+}
```

And edit `AgbMain`:

```diff
	...
	RtcInit();
	CheckForFlashMemory();
	InitMainCallbacks();
	InitMapMusic();
+	SeedRngWithRtc();
	ClearDma3Requests();
	...
```

This restores the code of Ruby/Sapphire.

**Alternate Fix:** Edit the following function in [src/title_screen.c](https://github.com/pret/pokeemerald/blob/master/src/title_screen.c):

```diff
void CB2_InitTitleScreen(void)
{
	switch (gMain.state)
	{
	default:
	case 0:
		SetVBlankCallback(NULL);
+		StartTimer1();
		SetGpuReg(REG_OFFSET_BLDCNT, 0);
		SetGpuReg(REG_OFFSET_BLDALPHA, 0);
		SetGpuReg(REG_OFFSET_BLDY, 0);
		...
```
This matches what FRLG does and obtains the seed differently than RS, independently of the RTC.

## Scrolling through items in the bag causes the image to flicker

**Fix:** Add the following function to [src/item_menu_icons.c](https://github.com/pret/pokeemerald/blob/master/src/item_menu_icons.c):
```diff
+void HideBagItemIconSprite(u8 id)
+{
+	u8 *spriteId = &gBagMenu->spriteId[10];
+	if (spriteId[id] != 0xFF)
+	{
+		gSprites[spriteId[id]].invisible = TRUE;
+	}
+}

```

and its corresponding declaration in [include/item_menu_icons.h](https://github.com/pret/pokeemerald/blob/master/include/item_menu_icons.h):

```diff
+void HideBagItemIconSprite(u8 id);

```

Then edit `BagMenu_MoveCursorCallback` in [src/item_menu.c](https://github.com/pret/pokeemerald/blob/master/src/item_menu.c):

```diff
	...
{
-	RemoveBagItemIconSprite(1 ^ gBagMenu->unk81B_1);
+	HideBagItemIconSprite(gBagMenu->unk81B_1 ^ 1);
+	RemoveBagItemIconSprite(gBagMenu->unk81B_1);
	if (a != -2)
	...
```

## Pokémon that have an affine transform as part of their entry animation glitch when going in and out of Poké Balls without a screen transition in between

**Fix:** Edit `sub_817F77C` in [src/pokemon_animation.c](https://github.com/pret/pokeemerald/blob/master/src/pokemon_animation.c#L1028):

```diff
    ...
-#ifdef BUGFIX
    else
    {
        // FIX: Reset these back to normal after they were changed so Poké Ball catch/release
        // animations without a screen transition in between don't break
        sprite->affineAnimPaused = FALSE;
        sprite->affineAnims = gUnknown_082FF694;
    }
-#endif // BUGFIX
}
```