merge with master

[ardour.git] / libs / gtkmm2ext / fastmeter.cc

diff --git a/libs/gtkmm2ext/fastmeter.cc b/libs/gtkmm2ext/fastmeter.cc
index 79d287145995b8b44a5051793e9ab010a9e3085c..a2b9e5fe1278bd9e34998c307e2deb6c07d91a3a 100644 (file)
--- 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)
+       */
+
+       // Clip range top
+       cairo_pattern_add_color_stop_rgb (pat, 0.0,
+                                         r3/255.0, g3/255.0, b3/255.0);
+
+       // 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);
 
-       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
+       // 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 (_p, false));
+       Cairo::RefPtr<Cairo::Pattern> p (new Cairo::Pattern (pat, false));
 
        return p;
 }