feat(main): implement def resolve_app_icon

scanslicer/main.py

@@ -146,3 +146,30 @@ def apply_global_text_size_offset(app, pixel_offset=2):
         font.setPointSizeF(point_size + (pixel_offset * 0.75))
 
     app.setFont(font)
+
+
+# resolve_app_icon: function definition for ScanSlicer behavior.
+def resolve_app_icon():
+    icon = QIcon.fromTheme("scanslicer")
+    if not icon.isNull():
+        return icon
+
+    appdir = os.environ.get("APPDIR", "").strip()
+    if not appdir:
+        return QIcon()
+
+    candidates = (
+        os.path.join(appdir, "usr", "share", "icons", "scanslicer.png"),
+        os.path.join(appdir, "usr", "share", "icons", "scanslicer.svg"),
+        os.path.join(appdir, "usr", "share", "pixmaps", "scanslicer.png"),
+        os.path.join(appdir, "usr", "share", "pixmaps", "scanslicer.svg"),
+        os.path.join(appdir, ".DirIcon"),
+    )
+    for candidate_path in candidates:
+        if not os.path.exists(candidate_path):
+            continue
+        candidate_icon = QIcon(candidate_path)
+        if not candidate_icon.isNull():
+            return candidate_icon
+
+    return QIcon()