Scan: RetroDECK is found wherever it is installed

internal/presets/linux_scan_test.go

@@ -288,6 +288,37 @@ func TestRetroDECKDetection(t *testing.T) {
 	}
 }
 
+// RetroDECK installed in a folder of the user's choosing, as a user had it:
+// ~/Games/Retrodeck/retrodeck/saves. Its systems are found there too.
+func TestRetroDECKDetection_ChosenFolder(t *testing.T) {
+	t.Setenv("XDG_DATA_HOME", "")
+	t.Setenv("XDG_CONFIG_HOME", "")
+	home := t.TempDir()
+	for _, system := range []string{"ps2", "snes"} {
+		p := filepath.Join(home, "Games", "Retrodeck", "retrodeck", "saves", system)
+		if err := os.MkdirAll(p, 0o777); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(filepath.Join(p, "game.srm"), []byte("x"), 0o666); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	sc := &Scanner{CacheFile: filepath.Join(t.TempDir(), "cache.json"), GOOS: "linux", HomeDir: home}
+	got := map[string]string{}
+	for _, d := range sc.Scan(nil) {
+		if strings.HasPrefix(d.ID, "retrodeck-") {
+			got[d.ID] = d.SavePath
+		}
+	}
+	for _, system := range []string{"ps2", "snes"} {
+		want := filepath.Join(home, "Games", "Retrodeck", "retrodeck", "saves", system)
+		if got["retrodeck-"+system] != want {
+			t.Errorf("%s: found at %q, want %q (all: %v)", system, got["retrodeck-"+system], want, got)
+		}
+	}
+}
+
 // TestPresetGlobPaths: SD-card style wildcard locations resolve through
 // filepath.Glob.
 func TestPresetGlobPaths(t *testing.T) {

internal/presets/presets.go

@@ -189,13 +189,17 @@ var presetDefs = []preset{
 		}},
 
 	// RetroDECK keeps every system's saves in one tree as well:
-	// retrodeck/saves/<system>, in the home folder, or on an SD card when it
-	// was moved there.
+	// retrodeck/saves/<system>. Its folder is always named retrodeck, but it
+	// goes wherever the user chose: the home folder by default, a folder in
+	// it (~/Games/Retrodeck/retrodeck, as a user had it), or an SD card.
 	{ID: "retrodeck", Name: "RetroDECK", Type: "emulator", IsWrapper: true,
 		LinuxPath: []string{
 			"~/retrodeck/saves",
+			"~/*/retrodeck/saves",
+			"~/*/*/retrodeck/saves",
 			"/run/media/*/retrodeck/saves",
 			"/run/media/*/*/retrodeck/saves",
+			"/run/media/*/*/*/retrodeck/saves",
 		}},
 
 	// Steam-emulator / repack wrappers (each subfolder = one game). These