pokeemerald/docs/bugs_and_glitches.md
2020-12-12 22:42:29 -08:00

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# 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
}
```