Crt, Ripple and Glitch take a level, 0 to 3, tunable at run time

Coordinator's request: `Crt 0..3` (likewise Ripple, Glitch), 0 off, `on`
the default level 2 (the polished rewrite), `off` and a bare word as
before. The level is one uniform (pardesLevel, beside pardesOpaque in the
prefix's own block); each pass picks its constants by it. Level 3 is at
least as strong as the old effects, measured as pixels changed by more
than 8 in a channel against a plain frame: Crt 18.3% (old 17.4%), Ripple
11.1% (9.5%), Glitch 9.3% a frame (8.1%); Glitch's level raises how often
it bursts as well as how hard. Config and ctl report `Crt 2` / `Crt off`.

Shared files touched: ninep/ctl.zig (the report line). Not touched:
pardes.zig, Messages.zig, mouse.zig, gui.zig, detached/*.

1 files changed, 22 insertions, 12 deletions

diff --git a/shaders/prebuilt/post-ripple.frag.glsl b/shaders/prebuilt/post-ripple.frag.glsl
index 28059def..d29a4c22 100644
--- a/shaders/prebuilt/post-ripple.frag.glsl
+++ b/shaders/prebuilt/post-ripple.frag.glsl
@@ -39,12 +39,19 @@ layout(set = 3, binding = 0, std140) uniform Globals {
     uniform vec3  iSelectionBackgroundColor;
 };
 
-// pardes's own: 1 when the window is opaque, so a pass cannot punch holes
-// in it through its alpha.
+// pardes's own: pardesOpaque is 1 when the window is opaque, so a pass
+// cannot punch holes in it through its alpha; pardesLevel is a bundled
+// pass's strength, 1 to 3 (`Crt 3`), and 0 for a user's file.
 layout(set = 3, binding = 1, std140) uniform PardesPost {
     float pardesOpaque;
+    float pardesLevel;
 };
 
+// A bundled pass's constant at levels 1, 2 and 3.
+float pardesByLevel(float one, float two, float three) {
+    return pardesLevel < 1.5 ? one : (pardesLevel < 2.5 ? two : three);
+}
+
 #define CURSORSTYLE_BLOCK        0
 #define CURSORSTYLE_BLOCK_HOLLOW 1
 #define CURSORSTYLE_BAR          2
@@ -67,19 +74,22 @@ void main() {
 #line 1
 // Ripple: the page as a still pool a slow swell crosses. Rings travel out
 // from the middle of the window at a fixed speed in pixels, so they look
-// the same at any size and frame rate; the displacement is at most a couple
-// of pixels, so text stays readable, and it eases in over its first half
+// the same at any size and frame rate; at the default level the displacement
+// is at most a couple of pixels, so text stays readable, and it eases in over its first half
 // second instead of snapping on. Each ring catches the light a little on its
 // rising side, in linear light, and the result is dithered so the shading
 // never bands. It is a Shadertoy file: pardes puts its prefix before it.
 
 const float TAU = 6.28318530718;
-const float WAVELENGTH_PX = 150.0;
-const float SPEED_PX = 55.0;        // outward, per second
-const float AMPLITUDE_PX = 2.2;
-const float SHADE = 0.035;          // light on a slope, linear
 const float EASE_IN = 0.5;          // seconds
 
+// Each at levels 1, 2 and 3 (`Ripple 1`..`Ripple 3`); 2 is the default.
+float wavelengthPx() { return pardesByLevel(170.0, 150.0, 120.0); }
+float speedPx() { return pardesByLevel(40.0, 55.0, 80.0); }        // outward, per second
+float amplitudePx() { return pardesByLevel(1.2, 2.2, 5.0); }
+float shade() { return pardesByLevel(0.02, 0.035, 0.09); }         // light on a slope, linear
+float reachEnd() { return pardesByLevel(0.85, 0.95, 1.3); }        // how far out it dies away
+
 vec3 toLinear(vec3 c) {
     return mix(pow((c + 0.055) / 1.055, vec3(2.4)), c / 12.92, lessThanEqual(c, vec3(0.04045)));
 }
@@ -101,16 +111,16 @@ void mainImage(out vec4 fragColor, in vec2 fragCoord) {
     float reach = 0.5 * length(size);
     // Strongest a third of the way out, fading to nothing at the middle
     // and at the edges, so the window's frame never wobbles.
-    float envelope = smoothstep(0.0, 0.18, radius / reach) * (1.0 - smoothstep(0.35, 0.95, radius / reach));
+    float envelope = smoothstep(0.0, 0.18, radius / reach) * (1.0 - smoothstep(0.35, reachEnd(), radius / reach));
     float ease = smoothstep(0.0, EASE_IN, iTime);
-    float phase = (radius - iTime * SPEED_PX) * TAU / WAVELENGTH_PX;
+    float phase = (radius - iTime * speedPx()) * TAU / wavelengthPx();
     float height = sin(phase);
     float slope = cos(phase);
     vec2 dir = offset / max(radius, 1e-3);
-    vec2 moved = fragCoord + dir * height * AMPLITUDE_PX * envelope * ease;
+    vec2 moved = fragCoord + dir * height * amplitudePx() * envelope * ease;
 
     vec4 s = texture(iChannel0, moved / size);
-    vec3 col = toLinear(s.rgb) * (1.0 + SHADE * slope * envelope * ease);
+    vec3 col = toLinear(s.rgb) * (1.0 + shade() * slope * envelope * ease);
     vec3 srgb = toSrgb(col) + (ign(fragCoord + float(iFrame % 64) * 5.588238) - 0.5) / 255.0;
     fragColor = vec4(clamp(srgb, 0.0, 1.0), s.a);
 }