Add Plugin system

Plugins are used to extend the functionality, without needing to poke around in
the original source code.

README.md

@@ -81,6 +81,15 @@ Bar:
 Audio Flyin: 
 - Audio control
 
+## Plugins
+gBar utilizes a plugin system for custom widgets.
+Plugins are native shared-libraries, which need to be placed inside ```~/.local/lib/gBar```, ```/usr/lib/gBar``` or ```/usr/local/lib/gBar```.
+Inside example/ there is an example plugin setup. To build and run it, run the following commands:
+
+```meson setup build -Dprefix=~/.local``` for the local user or ```meson setup build``` for all users\
+```ninja -C build install```\
+```gBar gBarHelloWorld``` The second argument is the name of the shared library (without 'lib' and '.so').
+
 
 ## FAQ
 ### There are already many GTK bars out there, why not use them?
@@ -102,9 +111,6 @@ If you have SASS installed: Edit ~/.config/gBar/style.scss and regenerate style.
 
 Else: Edit ~/.config/gBar/style.css directly!
 
-### I want to modify the widgets behaviour/Add my own widgets
-Unfortunately, you need to implement it yourself in C++. For inspiration look into src/Bar.cpp or src/AudioFlyin.cpp, or open an issue(Maybe I'll implement it for you).
-
 ### The Audio widget doesn't open
 Delete /tmp/gBar__audio.
 This happens, when you kill the widget before it closes automatically after a few seconds.

example/main.cpp

@@ -0,0 +1,12 @@
+#include <gBar/Common.h>
+#include <gBar/Window.h>
+
+void Create(Window& window, int32_t monitor)
+{
+    auto mainWidget = Widget::Create<Text>();
+    mainWidget->SetText("Hello, World!");
+
+    window = Window(std::move(mainWidget), monitor);
+}
+
+DEFINE_PLUGIN(Create);

example/meson.build

@@ -0,0 +1,18 @@
+project('gBarHelloWorld',
+        ['cpp'],
+        version: '0.0.1',
+        license: 'MIT',
+        meson_version: '>=0.45.1',
+        default_options: ['c_std=c++17', 'warning_level=3'])
+
+# Important!
+gtk = dependency('gtk+-3.0')
+
+gBar = dependency('gBar')
+
+library(
+  'gBarHelloWorld',
+  ['main.cpp'],
+  dependencies: [gBar],
+  install: true,
+  install_dir: 'lib/gBar/')

meson.build

@@ -2,17 +2,27 @@ project('gBar',
     ['cpp'],
     version: '0.0.1',
     license: 'MIT',
-    meson_version: '>=0.45.1',
+    meson_version: '>=0.46.0',
     default_options: ['c_std=c++17', 'warning_level=3'])
 
 gtk = dependency('gtk+-3.0')
 gtk_layer_shell = dependency('gtk-layer-shell-0')
 
+headers = [
+  'src/Common.h',
+  'src/System.h',
+  'src/PulseAudio.h',
+  'src/Widget.h',
+  'src/Window.h',
+]
+
 if get_option('HasHyprland')
   add_global_arguments('-DHAS_HYPRLAND', language: 'cpp')
+  headers += 'src/NvidiaGPU.h'
 endif
 if get_option('HasNvidia')
   add_global_arguments('-DHAS_NVIDIA', language: 'cpp')
+  headers += 'src/Hyprland.h'
 endif
 if get_option('HasBlueZ')
   add_global_arguments('-DHAS_BLUEZ', language: 'cpp')
@@ -23,16 +33,30 @@ endif
 
 pulse = dependency('libpulse')
 
-executable(
+libgBar = library('gBar', 
-  'gBar',
+  ['src/Window.cpp', 
-  ['src/gBar.cpp', 
-   'src/Window.cpp', 
    'src/Widget.cpp', 
    'src/System.cpp', 
    'src/Bar.cpp', 
    'src/AudioFlyin.cpp',
    'src/BluetoothDevices.cpp',
+   'src/Plugin.cpp'
   ],
   dependencies: [gtk, gtk_layer_shell, pulse],
+  install: true)
+
+pkg = import('pkgconfig')
+pkg.generate(libgBar)
+
+executable(
+  'gBar',
+  ['src/gBar.cpp'], 
+  dependencies: [gtk],
+  link_with: libgBar,
   install: true
 )
+
+install_headers(
+  headers,
+  subdir: 'gBar'
+)

src/Common.h

@@ -83,3 +83,17 @@ inline Process OpenProcess(Args... args)
         return {child};
     }
 }
+
+// Plugins
+#include "Window.h"
+#define DL_VERSION 1
+
+#define DEFINE_PLUGIN(fun)                                                \
+    extern "C" int32_t Plugin_GetVersion()                                \
+    {                                                                     \
+        return DL_VERSION;                                                \
+    };                                                                    \
+    extern "C" void Plugin_InvokeCreateFun(void* window, int32_t monitor) \
+    {                                                                     \
+        fun(*(Window*)window, monitor);                                   \
+    }

src/Plugin.cpp

@@ -0,0 +1,35 @@
+#include "Plugin.h"
+#include "Common.h"
+#include "Window.h"
+
+#include <dlfcn.h>
+
+void Plugin::LoadWidgetFromPlugin(const std::string& pluginName, Window& window, int32_t monitor)
+{
+    std::string home = std::getenv("HOME");
+    std::array<std::string, 3> paths = {home + "/.local/lib/gBar", "/usr/local/lib/gBar", "/usr/lib/gBar"};
+    // 1. Try and load plugin
+    void* dl;
+    for (auto& path : paths)
+    {
+        std::string soPath = path + "/lib" + pluginName + ".so";
+        dl = dlopen(soPath.c_str(), RTLD_NOW);
+        if (dl)
+            break;
+    }
+    ASSERT(dl, "Cannot find plugin library!");
+
+    typedef void (*PFN_InvokeCreateFun)(void*, int32_t);
+    typedef int32_t (*PFN_GetVersion)();
+    auto getVersion = (PFN_GetVersion)dlsym(dl, "Plugin_GetVersion");
+    ASSERT(getVersion, "DL is not a valid gBar plugin!");
+    ASSERT(getVersion() == DL_VERSION, "Mismatching version, please recompile your plugin!");
+
+    typedef void (*PFN_InvokeCreateFun)(void*, int32_t);
+    auto invokeCreateFun = (PFN_InvokeCreateFun)dlsym(dl, "Plugin_InvokeCreateFun");
+    ASSERT(invokeCreateFun, "DL is not a valid gBar plugin!");
+
+    // Execute
+    invokeCreateFun(&window, monitor);
+}
+

src/Plugin.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <string>
+#include "Window.h"
+
+namespace Plugin
+{
+    void LoadWidgetFromPlugin(const std::string& pluginName, Window& window, int32_t monitor);
+}

src/Window.cpp

@@ -1,6 +1,7 @@
 #include "Window.h"
 #include "Common.h"
 
+#include <gtk/gtk.h>
 #include <gtk-layer-shell.h>
 
 Window::Window(std::unique_ptr<Widget>&& mainWidget, int32_t monitor) : m_MainWidget(std::move(mainWidget)), m_Monitor(monitor) {}

src/gBar.cpp

@@ -4,9 +4,8 @@
 #include "Bar.h"
 #include "AudioFlyin.h"
 #include "BluetoothDevices.h"
+#include "Plugin.h"
 
-#include <gtk/gtk.h>
-#include <gtk-layer-shell.h>
 #include <cmath>
 #include <cstdio>
 #include <unistd.h>
@@ -50,6 +49,10 @@ int main(int argc, char** argv)
         BluetoothDevices::Create(window, monitor);
     }
 #endif
+    else
+    {
+        Plugin::LoadWidgetFromPlugin(argv[1], window, monitor);
+    }
 
     window.Run(argc, argv);