hyprland-wiki/pages/Plugins/Development/Advanced.md
2023-04-16 00:39:00 +01:00

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This page documents a few advanced things about the Hyprland Plugin API.
{{< toc >}}
## Using Function Hooks
{{< hint type=important >}}
Function hooks are only available on `AMD64` (`x86_64`).
Attempting to hook on any other arch will make Hyprland simply ignore your hooking attempt.
{{</ hint >}}
Function hooks are intimidating at first, but when used properly can be _extremely_ powerful.
Function hooks allow you to intercept any call to the function you hook.
Let's look at a simple example:
```cpp
void Events::listener_monitorFrame(void* owner, void* data)
```
will be the function we want to hook. `Events::` is a namespace, not a class, so this
is just a plain function.
```cpp
// make a global instance of a hook class for this hook
inline CFunctionHook* g_pMonitorFrameHook = nullptr;
// create a pointer typedef for the function we are hooking.
typedef void (*origMonitorFrame)(void*, void*);
// our hook
void hkMonitorFrame(void* owner, void* data) {
(*(origMonitorFrame)g_pMonitorFrameHook->m_pOriginal)(owner, data);
}
APICALL EXPORT PLUGIN_DESCRIPTION_INFO PLUGIN_INIT(HANDLE handle) {
// stuff...
// create the hook
static const auto METHODS = HyprlandAPI::findFunctionsByName(PHANDLE, "listener_monitorFrame");
g_pMonitorFrameHook = HyprlandAPI::createFunctionHook(handle, METHODS[0].address, (void*)&hkMonitorFrame);
// init the hook
g_pMonitorFrameHook->hook();
// further stuff...
}
```
We have just made a hook. Now, whenever Hyprland calls `Events::listener_monitorFrame`, our hook will be called instead!
This way, you can run code before / after the function, modify the inputs or results, or even block the function from executing.
`CFunctionHook` can also be unhooked whenever you please. Just run `unhook()`. It can be rehooked later by calling `hook()` again.
### Member functions
For members, e.g. `CCompositor::focusWindow(CWindow*, wlr_surface*)` you will also need to add the thisptr argument to your hook:
```cpp
typedef void (*origFocusWindow)(void*, CWindow*, wlr_surface*);
void hkFocusWindow(void* thisptr, CWindow* pWindow, wlr_surface* pSurface) {
// stuff...
// and if you want to call the original...
(*(origFocusWindow)g_pFocusWindowHook->m_pOriginal)(thisptr, pWindow, pSurface);
}
APICALL EXPORT PLUGIN_DESCRIPTION_INFO PLUGIN_INIT(HANDLE handle) {
// stuff...
static const auto METHODS = HyprlandAPI::findFunctionsByName(PHANDLE, "focusWindow");
g_pFocusWindowHook = HyprlandAPI::createFunctionHook(handle, METHODS[0].address, (void*)&hkFocusWindow);
g_pFocusWindowHook->hook();
// further stuff...
}
```
{{< hint type=warning >}}
Please note method lookups are slow and should not be used often. The entries _will not_ change during runtime, so it's a good idea
to make the lookups `static`.
{{</ hint >}}
### Why use findFunctionsByName?
Why use that instead of e.g. `&CCompositor::focusWindow`? Two reasons:
1 - less breakage. Whenever someone updates hyprland, that address might become invalid. findFunctionsByName is more resilient. As long as the function exists, it will be found.
2 - error handling. The method array contains, besides the address, the signatures. You can verify those to make 100% sure you got the right function, or throw an error if it was not found.
## Using the config
You can register config values in the `PLUGIN_INIT` function:
```cpp
APICALL EXPORT PLUGIN_DESCRIPTION_INFO PLUGIN_INIT(HANDLE handle) {
// stuff...
HyprlandAPI::addConfigValue(PHANDLE, "plugin:example:exampleInt", SConfigValue{.intValue = 1});
// further stuff...
}
```
Plugin variables ***must*** be in the `plugins:` category. Further categories are up to you. It's generally
a good idea to group all variables from your plugin in a subcategory with the plugin name, e.g. `plugins:myPlugin:variable1`.
For retrieving the values, call `HyprlandAPI::getConfigValue`.
Please remember that the pointer to your config value will never change after `PLUGIN_INIT`, so to greatly optimize performance, make it static:
```cpp
static auto* const MYVAR = &HyprlandAPI::getConfigValue(PHANDLE, "plugin:myPlugin:variable1")->intValue;
```
## Further
Read the API at `src/plugins/PluginAPI.hpp` and check out the examplePlugin in `examples/`.
And, most importantly, have fun!