feat: implement DSL for defining alternate substitution lookup

Dalgona · Jan 30, 2022 · ebe20b2 · ebe20b2
1 parent 7860962
commit ebe20b2
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Showing 2 changed files with 21 additions and 1 deletion.
diff --git a/lib/pixel_font/dsl/otf_layout/lookups/gsub.ex b/lib/pixel_font/dsl/otf_layout/lookups/gsub.ex
@@ -7,6 +7,7 @@ defmodule PixelFont.DSL.OTFLayout.Lookups.GSUB do
   alias PixelFont.DSL.OTFLayout.Lookups.Common
   alias PixelFont.Glyph
   alias PixelFont.TableSource.GSUB
+  alias PixelFont.TableSource.GSUB.Alternate1
   alias PixelFont.TableSource.GSUB.Ligature1
   alias PixelFont.TableSource.GSUB.ReverseChainingContext1
   alias PixelFont.TableSource.GSUB.Single1
@@ -32,6 +33,15 @@ defmodule PixelFont.DSL.OTFLayout.Lookups.GSUB do
     }
   end
 
+  def __handle_lookup__(:alternate) do
+    %{
+      imports: [substitutions__3: 1],
+      type: 3,
+      ast_transform: &replace_call(&1, :substitutions, 1, :substitutions__3),
+      runtime_transform: & &1
+    }
+  end
+
   def __handle_lookup__(:ligature) do
     %{
       imports: [substitutions__4: 1],
@@ -76,6 +86,16 @@ defmodule PixelFont.DSL.OTFLayout.Lookups.GSUB do
     end
   end
 
+  defmacro substitutions__3(do: do_block) do
+    quote do
+      (fn ->
+         import unquote(__MODULE__), only: [substitute: 2]
+
+         %Alternate1{alternatives: unquote(do_block |> get_exprs() |> elem(0))}
+       end).()
+    end
+  end
+
   defmacro substitutions__4(do: do_block) do
     quote do
       (fn ->

diff --git a/lib/pixel_font/table_source/gsub/alternate_1.ex b/lib/pixel_font/table_source/gsub/alternate_1.ex
@@ -3,7 +3,7 @@ defmodule PixelFont.TableSource.GSUB.Alternate1 do
 
   defstruct alternatives: %{}
 
-  @type t :: %__MODULE__{alternatives: %{optional(Glyph.id()) => [Glyph.id()]}}
+  @type t :: %__MODULE__{alternatives: [{Glyph.id(), [Glyph.id()]}]}
 
   defimpl PixelFont.TableSource.GSUB.Subtable do
     require PixelFont.Util