begin refactoring to use square pixels instead of triangles, focusing on functional core first

temp-squares/app-type.sml

@@ -0,0 +1,35 @@
+structure AppType =
+struct
+  datatype app_mode = NORMAL_MODE | BROWSE_MODE
+
+  datatype file_browser_item = IS_FILE of string | IS_FOLDER of string
+
+  type app_type =
+    { mode: app_mode
+    , squares: int vector vector
+    , canvasWidth: int
+    , canvasHeight: int
+    , windowWidth: int
+    , windowHeight: int
+    , xClickPoints: Real32.real vector
+    , yClickPoints: Real32.real vector
+
+    (* undo and redo commented out temporarily 
+    , undo: (Real32.real * Real32.real) list
+    , redo: (Real32.real * Real32.real) list
+    *)
+
+    , showGraph: bool
+    , mouseX: Real32.real
+    , mouseY: Real32.real
+    , arrowX: int
+    , arrowY: int
+    , openFilePath: string
+    , fileBrowser: file_browser_item vector
+    , fileBrowserIdx: int
+    , r: Real32.real
+    , g: Real32.real
+    , b: Real32.real
+    , modalNum: int
+    }
+end