Use cylindrical placement for key legends

examples/legends_dish.scad

@@ -0,0 +1,30 @@
+include <../includes.scad>
+
+/* here's how to use the legends() command.
+   The first argument is the legend itself, which can also be a whole string.
+   The second argument is the "position" of the legend relative to center.
+   Legends currently have to all be inset or outset at the same time, but you
+   can have as many of them as you want.
+   The numbers used are some magic constant, so just fudge them until it looks good.
+*/
+
+/* $outset_legends = true; */
+legends = ["A", "b", "c", "uwu"];
+
+$font_size = 4;
+
+for (x=[0,1,2,3,4]) {
+  for(y=[1,2,3])
+  translate_u(y * y / 2,x) {
+    u(y) cherry_row(x)
+    legend(legends[0], [-1,-1]) {
+      legend(legends[1], [1,-1]) {
+        legend(legends[2], [-1,1]) {
+          legend(legends[3], [-.8,0]) {
+            key();
+          }
+        }
+      }
+    }
+  }
+}

src/dishes/cylindrical.scad

@@ -8,9 +8,9 @@ module cylindrical_dish(width, height, depth, inverted){
    * the width of the keycap.
    */
   // the distance you have to move the dish so it digs in depth millimeters
-  chord_length = (pow(width, 2) - 4 * pow(depth, 2)) / (8 * depth);
+  chord_length = cylindrical_dish_chord_length(width=width, depth=depth);
   //the radius of the dish
-  rad = (pow(width, 2) + 4 * pow(depth, 2)) / (8 * depth);
+  rad = cylindrical_dish_radius(width=width, depth=depth);
   direction = inverted ? -1 : 1;
 
   translate([0,0, chord_length * direction]){

src/features/legends.scad

@@ -1,3 +1,5 @@
+use <libraries/text_on.scad>
+
 module keytext(text, position, font_size, depth) {
   woffset = (top_total_key_width()/3.5) * position[0];
   hoffset = (top_total_key_height()/3.5) * -position[1];
@@ -8,6 +10,39 @@ module keytext(text, position, font_size, depth) {
   }
 }
 
+module keytext_cylindrical(text, position, font_size, depth) {
+  woffset = (top_total_key_width()/3.5) * position[0];
+  hoffset = (top_total_key_height()/3.5) * -position[1] - font_size/2;
+  // copied from module _dish()
+  dish_width = top_total_key_width() + $dish_overdraw_width;
+  dish_height = top_total_key_height() + $dish_overdraw_height;
+  dish_rad = cylindrical_dish_radius(width=dish_width, depth=$dish_depth);
+  // XXX inverted legends
+  chord_length = cylindrical_dish_chord_length(width=dish_width, depth=$dish_depth);
+  dish_circumference = 6.283 * dish_rad;
+  theta = woffset * 360 / dish_circumference;
+  echo("dish radius =", dish_rad, "woffset = ", woffset, "theta =", theta);
+  translate([$dish_offset_x,0,chord_length]) {
+  mirror([1,0,0])
+  rotate(180)
+  rotate([90,0,0])
+    color($tertiary_color) {
+      text_on_cylinder(t=text,
+      r=dish_rad-.1,
+      h=top_total_key_height()/3.5,
+      updown=hoffset,
+      eastwest=theta,
+      face=$font, size=font_size,
+      // unsupported: halign="center", valign="center",
+      center=false,
+      cylinder_center=true,
+      extrusion_center=true,
+      extrusion_height = 2*depth,
+      rotate=0);
+    }
+  }
+}
+
 module legends(depth=0) {
   if (len($front_legends) > 0) {
     front_of_key() {
@@ -17,9 +52,16 @@ module legends(depth=0) {
     }
   }
   if (len($legends) > 0) {
-    top_of_key() {
-      for (i=[0:len($legends)-1]) {
-        keytext($legends[i][0], $legends[i][1], $legends[i][2], depth);
+    if($dish_type == "cylindrical"){
+    top_placement()
+        for (i=[0:len($legends)-1]) {
+          keytext_cylindrical($legends[i][0], $legends[i][1], $legends[i][2], depth);
+        }
+    } else {
+      top_of_key() {
+        for (i=[0:len($legends)-1]) {
+          keytext($legends[i][0], $legends[i][1], $legends[i][2], depth);
+        }
       }
     }
   }

src/functions.scad

@@ -47,3 +47,17 @@ function extra_keytop_length_for_flat_sides() = ($width_difference * vertical_in
 function add_rounding(p, radius)=[for(i=[0:len(p)-1])[p[i].x,p[i].y, radius]];
 // computes millimeter length from unit length
 function unit_length(length) = $unit * (length - 1) + 18.16;
+
+/* we do some funky math here
+ * basically you want to have the dish "dig in" to the keycap x millimeters
+ * in order to do that you have to solve a small (2d) system of equations
+ * where the chord of the spherical cross section of the dish is
+ * the width of the keycap.
+ */
+// the distance you have to move the dish so it digs in depth millimeters
+function cylindrical_dish_chord_length(width, depth) = 
+    (pow(width, 2) - 4 * pow(depth, 2)) / (8 * depth);
+
+//the radius of the dish
+function cylindrical_dish_radius(width, depth) =
+        (pow(width, 2) + 4 * pow(depth, 2)) / (8 * depth);