From f3a6b8a9bae2c926dd37315793416f14c176bbd8 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Wed, 31 Aug 2011 18:58:46 +0000
Subject: [PATCH] Fix meter colour range to again have a hard knee at 0dB and
 twiddle colours so >0dB levels are red and stand out.

I am not sure if this is the original intent here, but it seems the most informative/useful/standard/etc. Unfortunately the colour names in the configuration (min, mid, max, clip) are a bit confusing (starting to clip = "mid"?) but changing them would break things. Oh well.


git-svn-id: svn://localhost/ardour2/branches/3.0@10042 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 gtk2_ardour/ardour3_ui_default.conf | 14 ++++-----
 libs/gtkmm2ext/fastmeter.cc         | 44 ++++++++++++++++++++---------
 2 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/gtk2_ardour/ardour3_ui_default.conf b/gtk2_ardour/ardour3_ui_default.conf
index 303b9b3c27..196bb89710 100644
--- a/gtk2_ardour/ardour3_ui_default.conf
+++ b/gtk2_ardour/ardour3_ui_default.conf
@@ -51,14 +51,14 @@
     <Option name="measure line bar" value="d7d9d99c"/>
     <Option name="measure line beat" value="b5b5b576"/>
     <Option name="meter bar" value="626470ff"/>
-    <Option name="meter fill min" value="0000ffff"/>
+    <Option name="meter fill min" value="00ff00ff"/>
     <Option name="meter fill clip" value="ff0000ff"/>
-    <Option name="meter fill mid" value="73f9baff"/>
-    <Option name="meter fill max" value="00fd5dff"/>
-    <Option name="midi meter fill min" value="effaa100"/>
-    <Option name="midi meter fill clip" value="f83913ff"/>
-    <Option name="midi meter fill mid" value="8fc78e00"/>
-    <Option name="midi meter fill max" value="00f45600"/>
+    <Option name="meter fill mid" value="ffff00ff"/>
+    <Option name="meter fill max" value="991e1eff"/>
+    <Option name="midi meter fill min" value="3f542aff"/>
+    <Option name="midi meter fill clip" value="ff0000ff"/>
+    <Option name="midi meter fill mid" value="bfff80ff"/>
+    <Option name="midi meter fill max" value="991e1eff"/>
     <Option name="meter marker" value="f2425bff"/>
     <Option name="midi bus base" value="00000000"/>
     <Option name="midi frame base" value="393d3766"/>
diff --git a/libs/gtkmm2ext/fastmeter.cc b/libs/gtkmm2ext/fastmeter.cc
index 79d2871459..a2b9e5fe12 100644
--- a/libs/gtkmm2ext/fastmeter.cc
+++ b/libs/gtkmm2ext/fastmeter.cc
@@ -94,10 +94,16 @@ FastMeter::generate_meter_pattern (
 {
 	guint8 r0,g0,b0,r1,g1,b1,r2,g2,b2,r3,g3,b3,a;
 
-	/* clr0: color at top of the meter
-	      1: color at the knee
-              2: color half-way between bottom and knee
-	      3: color at the bottom of the meter
+	/*
+	  The knee is the hard transition point (e.g. at 0dB where the colors
+	  change dramatically to make clipping apparent). Thus there are two
+	  gradients in the pattern, the "normal range" and the "clip range", which
+	  are separated at the knee point.
+
+	  clr0: color at bottom of normal range gradient
+	  clr1: color at top of normal range gradient
+	  clr2: color at bottom of clip range gradient
+	  clr3: color at top of clip range gradient
 	*/
 
 	UINT_TO_RGBA (clr0, &r0, &g0, &b0, &a);
@@ -112,18 +118,30 @@ FastMeter::generate_meter_pattern (
 	//  return def / 115.0f
 
 	const int knee = (int)floor((float)height * 100.0f / 115.0f);
-	cairo_pattern_t* _p = cairo_pattern_create_linear (0.0, 0.0, width, height);
+	cairo_pattern_t* pat = cairo_pattern_create_linear (0.0, 0.0, width, height);
 
-	/* cairo coordinate space goes downwards as y value goes up, so invert
-	 * knee-based positions by using (1.0 - y)
-	 */
+	/*
+	  Cairo coordinate space goes downwards as y value goes up, so invert
+	  knee-based positions by using (1.0 - y)
+	*/
 
-	cairo_pattern_add_color_stop_rgb (_p, 0.0, r3/255.0, g3/255.0, b3/255.0); // bottom
-	cairo_pattern_add_color_stop_rgb (_p, 1.0 - (knee/(double)height), r2/255.0, g2/255.0, b2/255.0); // mid-point to knee
-	cairo_pattern_add_color_stop_rgb (_p, 1.0 - (knee/(2.0 * height)), r1/255.0, g1/255.0, b1/255.0); // knee to top
-	cairo_pattern_add_color_stop_rgb (_p, 1.0, r0/255.0, g0/255.0, b0/255.0); // top
+	// Clip range top
+	cairo_pattern_add_color_stop_rgb (pat, 0.0,
+	                                  r3/255.0, g3/255.0, b3/255.0);
 
-	Cairo::RefPtr<Cairo::Pattern> p (new Cairo::Pattern (_p, false));
+	// Clip range bottom
+	cairo_pattern_add_color_stop_rgb (pat, 1.0 - (knee/(double)height),
+	                                  r2/255.0, g2/255.0, b2/255.0);
+
+	// Normal range top (double-stop at knee)
+	cairo_pattern_add_color_stop_rgb (pat, 1.0 - (knee/(double)height),
+	                                  r1/255.0, g1/255.0, b1/255.0);
+
+	// Normal range bottom
+	cairo_pattern_add_color_stop_rgb (pat, 1.0,
+	                                  r0/255.0, g0/255.0, b0/255.0); // top
+
+	Cairo::RefPtr<Cairo::Pattern> p (new Cairo::Pattern (pat, false));
 
 	return p;
 }