font: constrain dingbats

This was a regression, we were giving dingbats an extra cell of
constraint width but not actually applying constraints to them.

src/font/nerd_font_attributes.zig

@@ -7,7 +7,7 @@
 const Constraint = @import("face.zig").RenderOptions.Constraint;
 
 /// Get the a constraints for the provided codepoint.
-pub fn getConstraint(cp: u21) Constraint {
+pub fn getConstraint(cp: u21) ?Constraint {
     return switch (cp) {
         0x2500...0x259f,
         => .{
@@ -1060,6 +1060,6 @@ pub fn getConstraint(cp: u21) Constraint {
             .align_vertical = .center,
             .group_width = 1.3001222493887530,
         },
-        else => .none,
+        else => null,
     };
 }

src/font/nerd_font_codegen.py

@@ -351,8 +351,8 @@ if __name__ == "__main__":
 const Constraint = @import("face.zig").RenderOptions.Constraint;
 
 /// Get the a constraints for the provided codepoint.
-pub fn getConstraint(cp: u21) Constraint {
+pub fn getConstraint(cp: u21) ?Constraint {
     return switch (cp) {
 """)
         f.write(generate_zig_switch_arms(patch_set, nerd_font))
-        f.write("\n        else => .none,\n    };\n}\n")
+        f.write("\n        else => null,\n    };\n}\n")

src/renderer/generic.zig

@@ -3066,7 +3066,14 @@ pub fn Renderer(comptime GraphicsAPI: type) type {
                     .thicken = self.config.font_thicken,
                     .thicken_strength = self.config.font_thicken_strength,
                     .cell_width = cell.gridWidth(),
-                    .constraint = getConstraint(cp),
+                    // If there's no Nerd Font constraint for this codepoint
+                    // then, if it's a symbol, we constrain it to fit inside
+                    // its cell(s), we don't modify the alignment at all.
+                    .constraint = getConstraint(cp) orelse
+                        if (cellpkg.isSymbol(cp)) .{
+                            .size_horizontal = .fit,
+                            .size_vertical = .fit,
+                        } else .none,
                     .constraint_width = constraintWidth(cell_pin),
                 },
             );