font: constrain width of two-cell icon-height icons

This stops things like folder icons from becoming over-wide. The patcher
typically makes these glyphs always 1 cell wide, but since we know how
it will be displayed we have the benefit of being able to make it more
than 1 cell when there's room. This makes our dynamic scaling *better*
than a static patched font :D

src/font/face.zig

@@ -205,7 +205,7 @@ pub const RenderOptions = struct {
         ) GlyphSize {
             var g = glyph;
 
-            const available_width: f64 = @floatFromInt(
+            var available_width: f64 = @floatFromInt(
                 metrics.cell_width * @min(
                     self.max_constraint_width,
                     constraint_width,
@@ -216,6 +216,22 @@ pub const RenderOptions = struct {
                 .icon => metrics.icon_height,
             });
 
+            // We make the opinionated choice here to reduce the width
+            // of icon-height symbols by the same amount horizontally,
+            // since otherwise wide aspect ratio icons like folders end
+            // up far too wide.
+            //
+            // But we *only* do this if the constraint width is 2, since
+            // otherwise it would make them way too small when sized for
+            // a single cell.
+            const is_icon_width = self.height == .icon and @min(self.max_constraint_width, constraint_width) > 1;
+            const orig_avail_width = available_width;
+            if (is_icon_width) {
+                const cell_height: f64 = @floatFromInt(metrics.cell_height);
+                const ratio = available_height / cell_height;
+                available_width *= ratio;
+            }
+
             const w = available_width -
                 self.pad_left * available_width -
                 self.pad_right * available_width;
@@ -327,6 +343,11 @@ pub const RenderOptions = struct {
                 .center => g.y = (h - g.height) / 2,
             }
 
+            // Add offset for icon width restriction, to keep it centered.
+            if (is_icon_width) {
+                g.x += (orig_avail_width - available_width) / 2;
+            }
+
             // Re-add our padding before returning.
             g.x += self.pad_left * available_width;
             g.y += self.pad_bottom * available_height;