SoundPlayer: Start working on a GUI sound player application

This can play anything that AWavLoader can load (so obviously only WAV
files at the moment.)

It works by having a timer that wakes up every 100ms and tries to send
a sample buffer to the AudioServer. If our server-side queue is full
then we wait until the next timer iteration and try again.

We display the most recently enqueued sample buffer in a nice little
widget that just plots the samples in green-on-black. :^)

Applications/SoundPlayer/SampleWidget.cpp

@@ -0,0 +1,45 @@
+#include "SampleWidget.h"
+#include <LibAudio/ABuffer.h>
+#include <LibGUI/GPainter.h>
+
+SampleWidget::SampleWidget(GWidget* parent)
+    : GFrame(parent)
+{
+    set_frame_shape(FrameShape::Container);
+    set_frame_shadow(FrameShadow::Sunken);
+    set_frame_thickness(2);
+}
+
+SampleWidget::~SampleWidget()
+{
+}
+
+void SampleWidget::paint_event(GPaintEvent& event)
+{
+    GFrame::paint_event(event);
+    GPainter painter(*this);
+    painter.add_clip_rect(event.rect());
+
+    painter.fill_rect(frame_inner_rect(), Color::Black);
+
+    if (!m_buffer)
+        return;
+
+    // FIXME: Right now we only display as many samples from the buffer as we can fit
+    //        in the frame_inner_rect(). Maybe scale the samples or something?
+    int samples_to_draw = min(m_buffer->sample_count(), frame_inner_rect().width());
+    for (int x = 0; x < samples_to_draw; ++x) {
+        // FIXME: This might look nicer if drawn as lines.
+        auto& sample = m_buffer->samples()[x];
+        Point p = { x, frame_inner_rect().center().y() + (int)(sample.left * frame_inner_rect().height()) };
+        painter.set_pixel(p, Color::Green);
+    }
+}
+
+void SampleWidget::set_buffer(ABuffer* buffer)
+{
+    if (m_buffer == buffer)
+        return;
+    m_buffer = buffer;
+    update();
+}