ALabel: Add support for configurable mouse events

This patch adds 3 new configuration options applicable for
subclasses of ALabel. The options can be used to execute
user defined code in response to the 3 mouse events:
* on-click: The left mouse button click
* on-scroll-up
* on-scroll-down
This patch also modifies the behaviour of the format-alt toggle
such that when the on-click event is configured, format-alt is
toggled on any mouse click other than left click. When on-click
is not defined, any mouse button would toggle format-alt.

Signed-off-by: Harish Krupo <harishkrupo@gmail.com>

include/ALabel.hpp

@@ -12,15 +12,22 @@ class ALabel : public IModule {
   virtual auto update() -> void;
   virtual std::string getIcon(uint16_t, const std::string& alt = "");
   virtual operator Gtk::Widget&();
+
  protected:
   Gtk::EventBox event_box_;
   Gtk::Label label_;
   const Json::Value& config_;
   std::string format_;
+  std::string button_press_cmd_ = "";
+  std::string scroll_up_cmd_ = "";
+  std::string scroll_down_cmd_ = "";
+  std::mutex mutex_;
+
  private:
   bool handleToggle(GdkEventButton* const& ev);
+  bool handleScroll(GdkEventScroll*);
   bool alt = false;
   const std::string default_format_;
 };
 
-}
+}  // namespace waybar

include/util/command.hpp

@@ -32,4 +32,21 @@ inline struct res exec(const std::string cmd)
   return {exit_code, output};
 }
 
+inline bool forkExec(std::string cmd) {
+  if (cmd == "") return true;
+
+  printf("fork exec command %s\n", cmd.c_str());
+  int32_t pid = fork();
+
+  if (pid < 0) {
+    printf("Unable to exec cmd %s, error %s", cmd.c_str(), strerror(errno));
+    return false;
   }
+
+  // Child executes the command
+  if (!pid) execl("/bin/sh", "sh", "-c", cmd.c_str(), (char*)0);
+
+  return true;
+}
+
+}  // namespace waybar::util::command

src/ALabel.cpp

@@ -1,4 +1,5 @@
 #include "ALabel.hpp"
+#include <util/command.hpp>
 
 #include <iostream>
 
@@ -14,30 +15,94 @@ waybar::ALabel::ALabel(const Json::Value& config, const std::string format)
   }
   if (config_["format-alt"].isString()) {
     event_box_.add_events(Gdk::BUTTON_PRESS_MASK);
-    event_box_.signal_button_press_event()
-      .connect(sigc::mem_fun(*this, &ALabel::handleToggle));
+    event_box_.signal_button_press_event().connect(
+        sigc::mem_fun(*this, &ALabel::handleToggle));
+  }
+
+  // configure events' user commands
+  if (config_["on-click"].isString()) {
+    std::string cmd = config_["on-click"].asString();
+    event_box_.add_events(Gdk::BUTTON_PRESS_MASK);
+    event_box_.signal_button_press_event().connect(
+      sigc::mem_fun(*this, &ALabel::handleToggle));
+
+    button_press_cmd_ = cmd;
+  }
+  if (config_["on-scroll-up"].isString()) {
+    std::string cmd = config_["on-scroll-up"].asString();
+    event_box_.add_events(Gdk::SCROLL_MASK);
+    event_box_.signal_scroll_event().connect(
+      sigc::mem_fun(*this, &ALabel::handleScroll));
+
+    scroll_up_cmd_ = cmd;
+  }
+  if (config_["on-scroll-down"].isString()) {
+    std::string cmd = config_["on-scroll-down"].asString();
+    event_box_.add_events(Gdk::SCROLL_MASK);
+    event_box_.signal_scroll_event().connect(
+      sigc::mem_fun(*this, &ALabel::handleScroll));
+
+    scroll_down_cmd_ = cmd;
   }
 }
 
-auto waybar::ALabel::update() -> void
-{
+auto waybar::ALabel::update() -> void {
   // Nothing here
 }
 
-bool waybar::ALabel::handleToggle(GdkEventButton* const& /*ev*/)
-{
+bool waybar::ALabel::handleToggle(GdkEventButton* const& e) {
+  if (button_press_cmd_ != "" && e->button == 1) {
+    waybar::util::command::forkExec(button_press_cmd_);
+  } else {
     alt = !alt;
     if (alt) {
       format_ = config_["format-alt"].asString();
     } else {
       format_ = default_format_;
     }
+  }
+
   dp.emit();
   return true;
 }
 
-std::string waybar::ALabel::getIcon(uint16_t percentage, const std::string& alt)
+bool waybar::ALabel::handleScroll(GdkEventScroll* e) {
+
+  // Avoid concurrent scroll event
   {
+    std::lock_guard<std::mutex> lock(mutex_);
+    bool direction_up = false;
+
+    if (e->direction == GDK_SCROLL_UP) {
+      direction_up = true;
+    }
+    if (e->direction == GDK_SCROLL_DOWN) {
+      direction_up = false;
+    }
+    if (e->direction == GDK_SCROLL_SMOOTH) {
+      gdouble delta_x, delta_y;
+      gdk_event_get_scroll_deltas(reinterpret_cast<const GdkEvent*>(e),
+                                  &delta_x, &delta_y);
+      if (delta_y < 0) {
+        direction_up = true;
+      } else if (delta_y > 0) {
+        direction_up = false;
+      }
+    }
+
+    if (direction_up)
+      waybar::util::command::forkExec(scroll_up_cmd_);
+    else
+      waybar::util::command::forkExec(scroll_down_cmd_);
+
+    dp.emit();
+  }
+
+  return true;
+}
+
+std::string waybar::ALabel::getIcon(uint16_t percentage,
+                                    const std::string& alt) {
   auto format_icons = config_["format-icons"];
   if (format_icons.isObject()) {
     if (!alt.empty() && format_icons[alt].isString()) {
@@ -57,6 +122,4 @@ std::string waybar::ALabel::getIcon(uint16_t percentage, const std::string& alt)
   return "";
 }
 
-waybar::ALabel::operator Gtk::Widget &() {
-  return event_box_;
-}
+waybar::ALabel::operator Gtk::Widget&() { return event_box_; }