pulseaudio: Change volume on scroll event

Subscribe for mouse scroll events on the pulseaudio widget
and change volume when event is received.
Scroll up increments the volume and scroll down decrements it.
These events are only subscibed when there are no user defined
commands present for them.

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

include/modules/pulseaudio.hpp

@@ -1,7 +1,8 @@
 #pragma once
 
-#include <pulse/pulseaudio.h>
 #include <fmt/format.h>
+#include <pulse/pulseaudio.h>
+#include <pulse/volume.h>
 #include <algorithm>
 #include "ALabel.hpp"
 
@@ -18,6 +19,8 @@ class Pulseaudio : public ALabel {
     static void contextStateCb(pa_context*, void*);
     static void sinkInfoCb(pa_context*, const pa_sink_info*, int, void*);
     static void serverInfoCb(pa_context*, const pa_server_info*, void*);
+    static void volumeModifyCb(pa_context*, int, void*);
+    bool handleScroll(GdkEventScroll* e);
 
     const std::string getPortIcon() const;
 
@@ -26,9 +29,11 @@ class Pulseaudio : public ALabel {
     pa_context* context_;
     uint32_t sink_idx_{0};
     uint16_t volume_;
+    pa_cvolume pa_volume_;
     bool muted_;
     std::string port_name_;
     std::string desc_;
+    bool scrolling_;
 };
 
-}
+}  // namespace waybar::modules

src/modules/pulseaudio.cpp

@@ -1,9 +1,14 @@
 #include "modules/pulseaudio.hpp"
 
-waybar::modules::Pulseaudio::Pulseaudio(const Json::Value& config)
-  : ALabel(config, "{volume}%"), mainloop_(nullptr), mainloop_api_(nullptr),
-    context_(nullptr), sink_idx_(0), volume_(0), muted_(false)
-{
+waybar::modules::Pulseaudio::Pulseaudio(const Json::Value &config)
+    : ALabel(config, "{volume}%"),
+      mainloop_(nullptr),
+      mainloop_api_(nullptr),
+      context_(nullptr),
+      sink_idx_(0),
+      volume_(0),
+      muted_(false),
+      scrolling_(false) {
   label_.set_name("pulseaudio");
   mainloop_ = pa_threaded_mainloop_new();
   if (mainloop_ == nullptr) {
@@ -26,10 +31,18 @@ waybar::modules::Pulseaudio::Pulseaudio(const Json::Value& config)
     throw std::runtime_error("pa_mainloop_run() failed.");
   }
   pa_threaded_mainloop_unlock(mainloop_);
+
+  // define the pulse scroll events only when no user provided
+  // events are configured
+  if (!config["on-scroll-up"].isString() &&
+      !config["on-scroll-down"].isString()) {
+    event_box_.add_events(Gdk::SCROLL_MASK);
+    event_box_.signal_scroll_event().connect(
+        sigc::mem_fun(*this, &Pulseaudio::handleScroll));
+  }
 }
 
-waybar::modules::Pulseaudio::~Pulseaudio()
-{
+waybar::modules::Pulseaudio::~Pulseaudio() {
   mainloop_api_->quit(mainloop_api_, 0);
   pa_threaded_mainloop_stop(mainloop_);
   pa_threaded_mainloop_free(mainloop_);
@@ -58,6 +71,47 @@ void waybar::modules::Pulseaudio::contextStateCb(pa_context *c, void *data)
   }
 }
 
+bool waybar::modules::Pulseaudio::handleScroll(GdkEventScroll *e) {
+  // Avoid concurrent scroll event
+  bool direction_up = false;
+  // XXX/TODO: Change of 100 corresponds to 1%, does that always hold true?
+  uint16_t change = 100;
+  pa_cvolume pa_volume = pa_volume_;
+
+  if (scrolling_) {
+    return false;
+  }
+  scrolling_ = true;
+  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) {
+    if (volume_ + 1 < 100) pa_cvolume_inc(&pa_volume, change);
+  } else {
+    if (volume_ - 1 > 0) pa_cvolume_dec(&pa_volume, change);
+  }
+
+  pa_context_set_sink_volume_by_index(context_, sink_idx_, &pa_volume,
+                                      volumeModifyCb, this);
+
+  return true;
+}
+
 /*
  * Called when an event we subscribed to occurs.
  */
@@ -75,16 +129,29 @@ void waybar::modules::Pulseaudio::subscribeCb(pa_context* context,
   }
 }
 
+/*
+ * Called in response to a volume change request
+ */
+void waybar::modules::Pulseaudio::volumeModifyCb(pa_context *c, int success,
+                                                 void *data) {
+  auto pa = static_cast<waybar::modules::Pulseaudio *>(data);
+  if (success) {
+    pa_context_get_sink_info_by_index(pa->context_, pa->sink_idx_, sinkInfoCb,
+                                      data);
+  }
+}
+
 /*
  * Called when the requested sink information is ready.
  */
-void waybar::modules::Pulseaudio::sinkInfoCb(pa_context* /*context*/,
-  const pa_sink_info* i, int /*eol*/, void* data)
-{
+void waybar::modules::Pulseaudio::sinkInfoCb(pa_context * /*context*/,
+                                             const pa_sink_info *i, int /*eol*/,
+                                             void *data) {
   if (i != nullptr) {
     auto pa = static_cast<waybar::modules::Pulseaudio *>(data);
-    float volume = static_cast<float>(pa_cvolume_avg(&(i->volume)))
-      / float{PA_VOLUME_NORM};
+    pa->pa_volume_ = i->volume;
+    float volume = static_cast<float>(pa_cvolume_avg(&(pa->pa_volume_))) /
+                   float{PA_VOLUME_NORM};
     pa->sink_idx_ = i->index;
     pa->volume_ = std::round(volume * 100.0f);
     pa->muted_ = i->mute != 0;
@@ -141,8 +208,11 @@ auto waybar::modules::Pulseaudio::update() -> void
     label_.get_style_context()->remove_class("muted");
     label_.get_style_context()->add_class("bluetooth");
   }
-  label_.set_label(fmt::format(format,
-    fmt::arg("volume", volume_),
-    fmt::arg("icon", getIcon(volume_, getPortIcon()))));
+  label_.set_label(
+      fmt::format(format, fmt::arg("volume", volume_),
+                  fmt::arg("icon", getIcon(volume_, getPortIcon()))));
   label_.set_tooltip_text(desc_);
+  if (scrolling_) {
+    scrolling_ = false;
+  }
 }