From 54bf3bae3d72dfce0f0517e1c82926ef22aad028 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Thu, 29 Oct 2015 20:50:22 +0100
Subject: [PATCH] Show the +/-1 dB target range.

---
 ui_mainwindow.ui |  2 +-
 vumeter.cpp      | 28 +++++++++++++++++++++-------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/ui_mainwindow.ui b/ui_mainwindow.ui
index 12e3864..c4a1d7c 100644
--- a/ui_mainwindow.ui
+++ b/ui_mainwindow.ui
@@ -141,7 +141,7 @@
          <widget class="VUMeter" name="vu_meter" native="true">
           <property name="minimumSize">
            <size>
-            <width>30</width>
+            <width>20</width>
             <height>0</height>
            </size>
           </property>
diff --git a/vumeter.cpp b/vumeter.cpp
index ab649bc..27ffc5a 100644
--- a/vumeter.cpp
+++ b/vumeter.cpp
@@ -4,6 +4,20 @@
 
 using namespace std;
 
+namespace {
+
+int lufs_to_pos(float level_lu, int height)
+{
+	const float min_level = 18.0f;    // y=0 is top of screen, so “min” is the loudest level.
+	const float max_level = -36.0f;
+	int y = lrintf(height * (level_lu - min_level) / (max_level - min_level));
+	y = std::max(y, 0);
+	y = std::min(y, height - 1);
+	return y;
+}
+
+}  // namespace
+
 VUMeter *global_vu_meter = nullptr;
 
 VUMeter::VUMeter(QWidget *parent)
@@ -17,6 +31,10 @@ void VUMeter::paintEvent(QPaintEvent *event)
 
 	painter.fillRect(0, 0, width(), height(), Qt::black);
 
+	int min_y = lufs_to_pos(1.0f, height());
+	int max_y = lufs_to_pos(-1.0f, height());
+	painter.fillRect(0, min_y, width(), max_y - min_y, Qt::green);
+
 	float level_lufs;
 	{
 		unique_lock<mutex> lock(level_mutex);
@@ -24,11 +42,7 @@ void VUMeter::paintEvent(QPaintEvent *event)
 	}
 
 	float level_lu = level_lufs + 23.0f;
-	const float min_level = 18.0f;    // y=0 is top of screen, so “min” is the loudest level.
-	const float max_level = -36.0f;
-	int y = lrintf(height() * (level_lu - min_level) / (max_level - min_level));
-	if (y >= 0 && y < height()) {
-		painter.setPen(Qt::white);
-		painter.drawLine(0, y, width(), y);
-	}
+	int y = lufs_to_pos(level_lu, height());
+	painter.setPen(Qt::white);
+	painter.drawLine(0, y, width(), y);
 }
-- 
2.39.2