X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=libs%2Fardour%2Fparameter_descriptor.cc;h=4f26af997d843087dca66a5c4d4ea6f5a7620ee6;hb=84272b4e27e537bf2c38c9cd25675c61addea40a;hp=9e02bc01ab1d3953a043af612cfbc599e29685f4;hpb=7ed775a716de655cee496e925fe062f6603abc0e;p=ardour.git

diff --git a/libs/ardour/parameter_descriptor.cc b/libs/ardour/parameter_descriptor.cc
index 9e02bc01ab..4f26af997d 100644
--- a/libs/ardour/parameter_descriptor.cc
+++ b/libs/ardour/parameter_descriptor.cc
@@ -157,13 +157,22 @@ ParameterDescriptor::update_steps()
 	if (toggled || enumeration) {
 		logarithmic = false;
 	}
+	if (logarithmic && sr_dependent && upper > lower && lower == 0) {
+		/* work-around for plugins with a log-scale control 0..SR; log (0) is not defined */
+		lower = upper / 1000.f;
+	}
 	if (logarithmic && (upper <= lower || lower * upper <= 0)) {
+		/* log-scale params need upper > lower and both values need the same sign */
 		logarithmic = false;
 	}
 	if (rangesteps < 2) {
 		rangesteps = 0;
 	}
 	if (enumeration) {
+		/* enums need scale-points.
+		 * The GUI is more restrictive, a dropdown is displayed
+		 * IIF  scale_points.size() == (1 + upper - lower)
+		 */
 		if (!scale_points || scale_points->empty ()) {
 			enumeration = false;
 		}
@@ -174,6 +183,13 @@ ParameterDescriptor::update_steps()
 		}
 	}
 
+	/* upper == lower does not make any sense */
+	if (lower == upper) {
+		upper = lower + 0.01; // add some arbitrary value
+	}
+
+	/* set steps */
+
 	if (unit == ParameterDescriptor::MIDI_NOTE) {
 		step      = smallstep = 1;  // semitone
 		largestep = 12;             // octave
@@ -184,45 +200,39 @@ ParameterDescriptor::update_steps()
 		largestep = position_to_gain (dB_coeff_step(upper));
 		step      = position_to_gain (largestep / 10.0);
 		smallstep = step;
+	} else if (logarithmic) {
+		/* ignore logscale rangesteps. {small|large}steps are used with the spinbox.
+		 * gtk-spinbox shows the internal (not interface) value and up/down
+		 * arrows linearly increase.
+		 * The AutomationController uses internal_to_interface():
+		 *   ui-step [0..1] -> log (1 + largestep / lower) / log (upper / lower)
+		 * so we use a step that's a multiple of "lower" for the interface step:
+		 *   log (1 + x) / log (upper / lower)
+		 */
+		smallstep = step = lower / 11;
+		largestep = lower / 3;
+		/* NOTE: the actual value does use rangesteps via
+		 * logscale_to_position_with_steps(), position_to_logscale_with_steps()
+		 * when it is converted.
+		 */
 	} else if (rangesteps > 1) {
 		const float delta = upper - lower;
-
-		step = smallstep = (delta / (rangesteps - 1)); // XXX
-		largestep = std::min ((delta / 5.0f), 10.f * smallstep); // XXX
-
-		if (logarithmic) {
-			smallstep = smallstep / logf (rangesteps); // XXX
-			step      = step      / logf (rangesteps);
-			largestep = largestep / logf (rangesteps);
-		} else if (integer_step) {
-			smallstep = 1.0;
-			step      = std::max(1.f, rintf (rangesteps));
-			largestep = std::max(1.f, rintf (largestep));
+		if (integer_step) {
+			smallstep = step = 1.0;
+			largestep = std::max(1.f, rintf (delta / (rangesteps - 1.f)));
+		} else {
+			step = smallstep = delta / (rangesteps - 1.f);
+			largestep = std::min ((delta / 4.0f), 10.f * smallstep);
 		}
 	} else {
 		const float delta = upper - lower;
-
-		/* 30 happens to be the total number of steps for a fader with default
-		   max gain of 2.0 (6 dB), so we use 30 here too for consistency. */
-		step      = smallstep = (delta / 300.0f);
-		largestep = (delta / 30.0f);
-
-		if (logarithmic) {
-			/* Steps are linear, but we map them with pow like values (in
-			   internal_to_interface).  Thus, they are applied exponentially,
-			   which means too few steps.  So, divide to get roughly the
-			   desired number of steps (30).  This is not mathematically
-			   precise but seems to be about right for the controls I tried.
-			   If you're reading this, you've probably found a case where that
-			   isn't true, and somebody needs to sit down with a piece of paper
-			   and actually do the math. */
-			smallstep = smallstep / logf(30.0f);
-			step      = step      / logf(30.0f);
-			largestep = largestep / logf(30.0f);
-		} else if (integer_step) {
-			smallstep = 1.0;
-			step      = std::max(1.f, rintf (step));
-			largestep = std::max(1.f, rintf (largestep));
+		/* 30 steps between min/max (300 for fine-grained) */
+		if (integer_step) {
+			smallstep = step = 1.0;
+			largestep = std::max(1.f, rintf (delta / 30.f));
+		} else {
+			step      = smallstep = (delta / 300.0f);
+			largestep = (delta / 30.0f);
 		}
 	}
 }
@@ -383,10 +393,10 @@ ParameterDescriptor::from_interface (float val) const
 				 * e.g. 5 integers 0,1,2,3,4 are mapped to a fader
 				 * [0.0 .. 0.2 | 0.2 .. 0.4 | 0.4 .. 0.6 | 0.6 .. 0.8 | 0.8 .. 1.0]
 				 */
-				val =  round (lower + val * (1.f + upper - lower) - .5f);
+				val = floor (lower + val * (1.f + upper - lower));
 			} else if (rangesteps > 1) {
 				/* similar to above, but for float controls */
-				val = floor (val * (rangesteps - 1.f)) / (rangesteps - 1.f); // XXX
+				val = round (val * (rangesteps - 1.f)) / (rangesteps - 1.f); // XXX
 				val = val * (upper - lower) + lower;
 			} else {
 				val = val * (upper - lower) + lower;