Adjust AppImage support for appimage.github.io

Environment variables are not reliable in that check environment.

Now the executable is under bin and the resources are in directories
under the same parent as bin. Path to the executable is obtained using
proc filesystem.

See AppImage/appimage.github.io#2994

Makefile

@@ -7,16 +7,17 @@ all:
 	alr build
 
 install: all
-	mkdir -p $(DESTDIR)
+	mkdir -p $(DESTDIR)/bin
 	cp -rp $(MAIN).desktop $(MAIN) themes $(DESTDIR)
+	cp -p bin/$(MAIN) $(DESTDIR)/bin
 	cp -p themes/1/icon.png $(DESTDIR)/$(MAIN).png
 
 AppImage:
 	rm -rf AppDir
-	make install DESTDIR=AppDir
+	make install DESTDIR=AppDir/usr
 	wget -nv -c https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage
 	chmod +x linuxdeploy-x86_64.AppImage
 	./linuxdeploy-x86_64.AppImage \
-	--executable $(MAIN) \
-	--desktop-file $(MAIN).desktop --icon-file=AppDir/$(MAIN).png \
+	--executable bin/$(MAIN) \
+	--desktop-file $(MAIN).desktop --icon-file=AppDir/usr/$(MAIN).png \
 	--appdir AppDir --output appimage

play_2048.gpr

@@ -11,15 +11,15 @@ project Play_2048 is
    for Source_Dirs use ("src");
    for Object_Dir use "obj";
    for Main use ("play_2048.adb");
-   for Exec_Dir use ".";
+   for Exec_Dir use "bin";
 
    package Compiler is
       for Default_Switches ("Ada") use
         ("-g",
          "-gnatQ",
          "-gnatwa",  -- All warnings
          "-gnatVa",  -- All validity checks
-         "-O1");
+         "-O2");
    end Compiler;
 
 end Play_2048;

src/play_2048.adb

@@ -16,7 +16,6 @@ with Ada.Numerics.Elementary_Functions; use Ada.Numerics.Elementary_Functions;
 with Ada.Command_Line;
 with Ada.Strings.Fixed;
 with Ada.Directories;
-with Ada.Environment_Variables;
 with Ada.Calendar.Formatting;
 
 with Storage;
@@ -211,10 +210,6 @@ procedure Play_2048 is
          (Move (Value, Length => 4, Justify => Ada.Strings.Center));
 
       Board : Game.t_Board renames State.Board;
-      Elapsed_Time : constant string := Ada.Calendar.Formatting.Image
-        (Elapsed_Time => Game.Elapsed_Time (State));
-      Best_Time_Image : constant String := Ada.Calendar.Formatting.Image
-        (Elapsed_Time => Best_Time);
    begin
       if Text_UI then
          Put_Line (Horizontal_Rule);
@@ -294,21 +289,24 @@ procedure Play_2048 is
    end Set_Text_Style;
 
    function Theme_Path (Theme_Id : t_theme) return String is
-      -- If running inside our AppImage, use the APPDIR env var. In
-      -- this way we allow running from an AppImage and still find the
+
+      Self_Exe : constant String := "/proc/self/exe";
+      -- Get the resources path through the directory where the program is
+      -- located.
+      -- In this way we allow running from an AppImage and still find the
       -- resource files.
       --
       App_Dir : constant String :=
-        (if Ada.Environment_Variables.Exists ("APPIMAGE") and then
-           Ada.Strings.Fixed.Index (Ada.Environment_Variables.Value ("APPIMAGE"),
-                                    "Play_2048") > 0 and then
-            Ada.Environment_Variables.Exists ("APPDIR")
+        (if Ada.Directories.Exists (Self_Exe)
          then
-            Ada.Environment_Variables.Value ("APPDIR") & "/"
-         else "");
+            Ada.Directories.Containing_Directory
+              (Ada.Directories.Containing_Directory
+                 (Ada.Directories.Full_Name (Self_Exe)))
+         else
+            "");
    begin
       return App_Dir &
-        "themes/" & Ada.Strings.Fixed.Trim (Theme_Id'Image,
+        "/themes/" & Ada.Strings.Fixed.Trim (Theme_Id'Image,
                                             Ada.Strings.Left) & "/";
    end Theme_Path;