resload

Reload the active resource pack in Minecraft Bedrock without leaving the world. An mcpelauncher mod for Linux and macOS.

Edit a texture or a JSON UI file, click a menu entry, see the change. No world reload, no game restart.

Build

Needs the Android NDK. The mod is loaded by mcpelauncher's own bionic linker, so it must be an Android aarch64 ELF even when built on macOS.

cmake -B build \
  -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake \
  -DANDROID_ABI=arm64-v8a \
  -DANDROID_PLATFORM=android-21 \
  -DMINECRAFT_SO=/path/to/versions/1.26.40.5/lib/arm64-v8a/libminecraftpe.so \
  -DOFFSETS_HEADER=$PWD/generated/offsets_1.26.40.5.h
cmake --build build

Install

Copy build/resload.so into the launcher's mods/ directory.

OS	Path
Linux	~/.local/share/mcpelauncher/mods/
macOS	~/Library/Application Support/mcpelauncher/mods/

Use

Menu bar, under resload:

Entry	What it reloads
Reload everything	Textures, atlases, models, and UI
Reload UI only	JSON UI definitions. Fastest.
Reload geometry + animation	Entity geometry and animations

Changes to existing files are picked up. Files added or deleted while the game is running are not; the pack repository is not rescanned.

Game versions

Every offset is specific to one build of libminecraftpe.so. On any other version the mod checks what the vtable slots actually point at, refuses to patch anything, and logs why:

[resload] handleReloadUIDefinitions: slot 13 holds 0x..., expected 0x...

That is a clean refusal, not a crash. Supporting a new version means adding a header to generated/.

How it works

The engine already has a full reload path; it runs when you change the pack selection in settings. Three MinecraftGame virtuals cover it:

onActiveResourcePacksChanged(ResourcePackManager&)
handleReloadUIDefinitions()
reloadAnimationAndGeometryData(bool sync)

All three are virtual, so the mod only writes vtable slots. No inline hooking, no code generation.

It needs two instance pointers. MinecraftGame* arrives as this in a per-frame vtable slot the mod hooks to get onto the game thread. ResourcePackManager* is captured from its own vtable, because the game hands it to listeners through the ResourcePackListener subobject, whose slot holds a this-adjusting thunk that branches straight to the implementation, so hooking the primary vtable slot never sees the call.

Menu clicks arrive on ImGui's thread. They set a flag, and the per-frame hook performs the reload on the game thread.

Troubleshooting

Run the launcher from a terminal to see the log. All output is prefixed [resload].

Message	Meaning
slot N holds 0x..., expected 0x...	Wrong game version for this build
no menu support in this launcher build	Launcher was built without ImGui
no MinecraftGame captured yet	Per-frame hook never fired; see RESLOAD_TICK_SLOT below

RESLOAD_TICK_SLOT overrides which vtable slot is hooked for the per-frame callback. It is the one value not derived from the binary, so it is settable without a rebuild.