C ABI plugin system

include/AModule.hpp

@@ -17,6 +17,7 @@ class AModule : public IModule {
   operator Gtk::Widget &() override;
   auto doAction(const std::string &name) -> void override;
 
+  /// Emitting on this dispatcher triggers a update() call
   Glib::Dispatcher dp;
 
  protected:

include/factory.hpp

@@ -91,6 +91,7 @@
 #include "modules/cava.hpp"
 #endif
 #include "bar.hpp"
+#include "modules/cffi.hpp"
 #include "modules/custom.hpp"
 #include "modules/image.hpp"
 #include "modules/temperature.hpp"

include/modules/cffi.hpp

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <string>
+
+#include "AModule.hpp"
+#include "util/command.hpp"
+#include "util/json.hpp"
+#include "util/sleeper_thread.hpp"
+
+namespace waybar::modules {
+
+namespace ffi {
+extern "C" {
+typedef struct wbcffi_module wbcffi_module;
+
+typedef struct {
+  wbcffi_module* obj;
+  const char* waybar_version;
+  GtkContainer* (*get_root_widget)(wbcffi_module*);
+  void (*queue_update)(wbcffi_module*);
+} wbcffi_init_info;
+
+struct wbcffi_config_entry {
+  const char* key;
+  const char* value;
+};
+}
+}  // namespace ffi
+
+class CFFI : public AModule {
+ public:
+  CFFI(const std::string&, const std::string&, const Json::Value&);
+  virtual ~CFFI();
+
+  virtual auto refresh(int signal) -> void override;
+  virtual auto doAction(const std::string& name) -> void override;
+  virtual auto update() -> void override;
+
+ private:
+  ///
+  void* cffi_instance_ = nullptr;
+
+  typedef void*(InitFn)(const ffi::wbcffi_init_info* init_info,
+                        const ffi::wbcffi_config_entry* config_entries, size_t config_entries_len);
+  typedef void(DenitFn)(void* instance);
+  typedef void(RefreshFn)(void* instance, int signal);
+  typedef void(DoActionFn)(void* instance, const char* name);
+  typedef void(UpdateFn)(void* instance);
+
+  // FFI hooks
+  struct {
+    std::function<InitFn> init = nullptr;
+    std::function<DenitFn> deinit = nullptr;
+    std::function<RefreshFn> refresh = [](void*, int) {};
+    std::function<DoActionFn> doAction = [](void*, const char*) {};
+    std::function<UpdateFn> update = [](void*) {};
+  } hooks_;
+};
+
+}  // namespace waybar::modules

man/waybar-cffi.5.scd

@@ -0,0 +1,37 @@
+waybar-cffi(5)
+# NAME
+
+waybar - cffi module
+
+# DESCRIPTION
+
+The *cffi* module gives full control of a GTK widget to a third-party dynamic library, to create more complex modules using different programming languages.
+
+# CONFIGURATION
+
+Addressed by *cffi/<name>*
+
+*module_path*: ++
+	typeof: string ++
+	The path to the dynamic library to load to control the widget.
+
+Some additional configuration may be required depending on the cffi dynamic library being used.
+
+
+# EXAMPLES
+
+## C example:
+
+An example module written in C can be found at https://github.com/Alexays/Waybar/resources/custom_modules/cffi_example/
+
+Waybar config to enable the module:
+```
+"cffi/c_example": {
+	"module_path": ".config/waybar/cffi/wb_cffi_example.so"
+}
+```
+
+
+# STYLE
+
+The classes and IDs are managed by the cffi dynamic library.

meson.build

@@ -190,6 +190,7 @@ if is_linux
     add_project_arguments('-DHAVE_MEMORY_LINUX', language: 'cpp')
     src_files += files(
         'src/modules/battery.cpp',
+        'src/modules/cffi.cpp',
         'src/modules/cpu.cpp',
         'src/modules/cpu_frequency/common.cpp',
         'src/modules/cpu_frequency/linux.cpp',
@@ -202,6 +203,7 @@ elif is_dragonfly or is_freebsd or is_netbsd or is_openbsd
     add_project_arguments('-DHAVE_CPU_BSD', language: 'cpp')
     add_project_arguments('-DHAVE_MEMORY_BSD', language: 'cpp')
     src_files += files(
+        'src/modules/cffi.cpp',
         'src/modules/cpu.cpp',
         'src/modules/cpu_frequency/bsd.cpp',
         'src/modules/cpu_frequency/common.cpp',
@@ -440,6 +442,7 @@ if scdoc.found()
         'waybar-backlight-slider.5.scd',
         'waybar-battery.5.scd',
         'waybar-cava.5.scd',
+        'waybar-cffi.5.scd',
         'waybar-clock.5.scd',
         'waybar-cpu.5.scd',
         'waybar-custom.5.scd',

resources/custom_modules/cffi_example/.gitignore

@@ -0,0 +1 @@
+.cache/

resources/custom_modules/cffi_example/README.md

@@ -0,0 +1,38 @@
+# C FFI module
+
+A C FFI module is a dynamic library that exposes standard C functions and
+constants, that Waybar can load and execute to create custom advanced widgets.
+
+Most language can implement the required functions and constants (C, C++, Rust,
+Go, Python, ...), meaning you can develop custom modules using your language of
+choice, as long as there's GTK bindings.
+
+Symbols to implement are documented in the
+[waybar_cffi_module.h](waybar_cffi_module.h) file.
+
+# Usage
+
+## Building this module
+
+```bash
+meson setup build
+meson compile -C build
+```
+
+## Load the module
+
+Edit your waybar config:
+```json
+{
+	// ...
+	"modules-center": [
+		// ...
+		"cffi/c_example"
+	],
+	// ...
+	"cffi/c_example": {
+		// Path to the compiled dynamic library file
+		"module_path": "resources/custom_modules/cffi_example/build/wb_cffi_example.so"
+	}
+}
+```

resources/custom_modules/cffi_example/main.c

@@ -0,0 +1,70 @@
+
+#include "waybar_cffi_module.h"
+
+typedef struct {
+  wbcffi_module* waybar_module;
+  GtkBox* container;
+  GtkButton* button;
+} ExampleMod;
+
+// This static variable is shared between all instances of this module
+static int instance_count = 0;
+
+void onclicked(GtkButton* button) {
+  char text[256];
+  snprintf(text, 256, "Dice throw result: %d", rand() % 6 + 1);
+  gtk_button_set_label(button, text);
+}
+
+// You must
+const size_t wbcffi_version = 1;
+
+void* wbcffi_init(const wbcffi_init_info* init_info, const wbcffi_config_entry* config_entries,
+                  size_t config_entries_len) {
+  printf("cffi_example: init config:\n");
+  for (size_t i = 0; i < config_entries_len; i++) {
+    printf("  %s = %s\n", config_entries[i].key, config_entries[i].value);
+  }
+
+  // Allocate the instance object
+  ExampleMod* inst = malloc(sizeof(ExampleMod));
+  inst->waybar_module = init_info->obj;
+
+  GtkContainer* root = init_info->get_root_widget(init_info->obj);
+
+  // Add a container for displaying the next widgets
+  inst->container = GTK_BOX(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 5));
+  gtk_container_add(GTK_CONTAINER(root), GTK_WIDGET(inst->container));
+
+  // Add a label
+  GtkLabel* label = GTK_LABEL(gtk_label_new("[Example C FFI Module:"));
+  gtk_container_add(GTK_CONTAINER(inst->container), GTK_WIDGET(label));
+
+  // Add a button
+  inst->button = GTK_BUTTON(gtk_button_new_with_label("click me !"));
+  g_signal_connect(inst->button, "clicked", G_CALLBACK(onclicked), NULL);
+  gtk_container_add(GTK_CONTAINER(inst->container), GTK_WIDGET(inst->button));
+
+  // Add a label
+  label = GTK_LABEL(gtk_label_new("]"));
+  gtk_container_add(GTK_CONTAINER(inst->container), GTK_WIDGET(label));
+
+  // Return instance object
+  printf("cffi_example inst=%p: init success ! (%d total instances)\n", inst, ++instance_count);
+  return inst;
+}
+
+void wbcffi_deinit(void* instance) {
+  printf("cffi_example inst=%p: free memory\n", instance);
+  free(instance);
+}
+
+void wbcffi_update(void* instance) { printf("cffi_example inst=%p: Update request\n", instance); }
+
+void wbcffi_refresh(void* instance, int signal) {
+  printf("cffi_example inst=%p: Received refresh signal %d\n", instance, signal);
+}
+
+void wbcffi_doaction(void* instance, const char* name) {
+  printf("cffi_example inst=%p: doAction(%s)\n", instance, name);
+}

resources/custom_modules/cffi_example/meson.build

@@ -0,0 +1,13 @@
+project(
+    'waybar_cffi_example', 'c',
+    version: '0.1.0',
+    license: 'MIT',
+)
+
+shared_library('wb_cffi_example',
+    ['main.c'],
+    dependencies: [
+        dependency('gtk+-3.0', version : ['>=3.22.0'])
+    ],
+    name_prefix: ''
+)

resources/custom_modules/cffi_example/waybar_cffi_module.h

@@ -0,0 +1,89 @@
+#pragma once
+
+#include <gtk/gtk.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/// Waybar ABI version. 1 is the latest version
+extern const size_t wbcffi_version;
+
+/// Private Waybar CFFI module
+typedef struct wbcffi_module wbcffi_module;
+
+/// Waybar module information
+typedef struct {
+  /// Waybar CFFI object pointer
+  wbcffi_module* obj;
+
+  /// Waybar version string
+  const char* waybar_version;
+
+  /// Returns the waybar widget allocated for this module
+  /// @param obj Waybar CFFI object pointer
+  GtkContainer* (*get_root_widget)(wbcffi_module* obj);
+
+  /// Queues a request for calling wbcffi_update() on the next GTK main event
+  /// loop iteration
+  /// @param obj Waybar CFFI object pointer
+  void (*queue_update)(wbcffi_module*);
+} wbcffi_init_info;
+
+/// Config key-value pair
+typedef struct {
+  /// Entry key
+  const char* key;
+  /// Entry value as string. JSON object and arrays are serialized.
+  const char* value;
+} wbcffi_config_entry;
+
+/// Module init/new function, called on module instantiation
+///
+/// MANDATORY CFFI function
+///
+/// @param init_info          Waybar module information
+/// @param config_entries     Flat representation of the module JSON config. The data only available
+///                           during wbcffi_init call.
+/// @param config_entries_len Number of entries in `config_entries`
+///
+/// @return A untyped pointer to module data, NULL if the module failed to load.
+void* wbcffi_init(const wbcffi_init_info* init_info, const wbcffi_config_entry* config_entries,
+                  size_t config_entries_len);
+
+/// Module deinit/delete function, called when Waybar is closed or when the module is removed
+///
+/// MANDATORY CFFI function
+///
+/// @param instance Module instance data (as returned by `wbcffi_init`)
+void wbcffi_deinit(void* instance);
+
+/// Called from the GTK main event loop, to update the UI
+///
+/// Optional CFFI function
+///
+/// @param instance Module instance data (as returned by `wbcffi_init`)
+/// @param action_name Action name
+void wbcffi_update(void* instance);
+
+/// Called when Waybar receives a POSIX signal and forwards it to each module
+///
+/// Optional CFFI function
+///
+/// @param instance Module instance data (as returned by `wbcffi_init`)
+/// @param signal Signal ID
+void wbcffi_refresh(void* instance, int signal);
+
+/// Called on module action (see
+/// https://github.com/Alexays/Waybar/wiki/Configuration#module-actions-config)
+///
+/// Optional CFFI function
+///
+/// @param instance Module instance data (as returned by `wbcffi_init`)
+/// @param action_name Action name
+void wbcffi_doaction(void* instance, const char* action_name);
+
+#ifdef __cplusplus
+}
+#endif

src/factory.cpp

@@ -201,6 +201,9 @@ waybar::AModule* waybar::Factory::makeModule(const std::string& name) const {
     if (ref.compare(0, 7, "custom/") == 0 && ref.size() > 7) {
       return new waybar::modules::Custom(ref.substr(7), id, config_[name]);
     }
+    if (ref.compare(0, 5, "cffi/") == 0 && ref.size() > 5) {
+      return new waybar::modules::CFFI(ref.substr(5), id, config_[name]);
+    }
   } catch (const std::exception& e) {
     auto err = fmt::format("Disabling module \"{}\", {}", name, e.what());
     throw std::runtime_error(err);