never end up with null skin pointer

app/CMakeLists.txt

@@ -57,6 +57,8 @@ qt_add_executable(${PROJECT_NAME}
     core/translation.hpp
     gui/overlay_widget.cpp
     gui/overlay_widget.hpp
+    skin/error_skin.cpp
+    skin/error_skin.hpp
 )
 
 set(APP_IDENTIFIER "com.github.kolcha.DigitalClock5")

app/core/skin_manager.cpp

@@ -12,6 +12,8 @@
 #include "skin/font_skin.hpp"
 #include "skin/legacy_skin.hpp"
 
+#include "skin/error_skin.hpp"
+
 struct SkinManager::Impl {
   QHash<QString, LegacySkinLoader> loaders;
   QSet<QString> user_skins;
@@ -75,7 +77,7 @@ std::unique_ptr<Skin> SkinManager::loadSkin(const QString& id) const
   for (auto iter = _impl->loaders.begin(); iter != _impl->loaders.end(); ++iter)
     if (iter->title() == id)
       return iter->skin();
-  return nullptr;
+  return std::make_unique<ErrorSkin>();
 }
 
 QStringList SkinManager::availableSkins() const

app/skin/error_skin.cpp

@@ -0,0 +1,61 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Nick Korotysh <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "error_skin.hpp"
+
+#include <QFontDatabase>
+#include <QPainter>
+
+namespace {
+
+class ErrorGlyph : public Skin::Glyph
+{
+public:
+  explicit ErrorGlyph(bool vis) noexcept
+      : _r(0, 0, 240, 100)
+      , _vis(vis)
+  {}
+
+  QRectF rect() const override { return _r; }
+  QPointF advance() const override { return {_r.width(), -_r.height()}; }
+
+  void draw(QPainter* p) const override;
+
+private:
+  QRectF _r;
+  bool _vis = true;
+};
+
+void ErrorGlyph::draw(QPainter* p) const
+{
+  p->save();
+  p->drawRoundedRect(_r.marginsRemoved({5, 5, 5, 5}), 8, 8);
+  auto fnt = QFontDatabase::systemFont(QFontDatabase::FixedFont);
+  p->setPen(QColor(0x8C, 0x8A, 0xFF));
+  fnt.setPointSize(14);
+  p->setFont(fnt);
+  p->drawText(_r.adjusted(0, 10, 0, -(_r.height() - 10 - 20)), "Digital Clock 5", {Qt::AlignCenter});
+  if (_vis) {
+    fnt.setPointSize(36);
+    p->setPen(QColor(0xF0, 0x40, 0x58));
+    p->setFont(fnt);
+    p->drawText(_r, "ERROR", {Qt::AlignCenter});
+  }
+  fnt.setPointSize(14);
+  p->setFont(fnt);
+  p->drawText(_r.adjusted(0, _r.height() - 10 - 20, 0, -10), "Skin Not Loaded", {Qt::AlignCenter});
+  p->restore();
+}
+
+} // namespace
+
+std::shared_ptr<Skin::Glyph> ErrorSkin::create(char32_t c) const
+{
+  if (c == ':' || c == ' ') {
+    return std::make_shared<ErrorGlyph>(c == ':');
+  }
+  return nullptr;
+}

app/skin/error_skin.hpp

@@ -0,0 +1,19 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Nick Korotysh <[email protected]>
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include "skin/skin.hpp"
+
+class ErrorSkin : public Skin
+{
+public:
+  bool hasAlternateSeparator() const override { return true; }
+  bool supportsCustomSeparator() const override { return false; }
+
+protected:
+  std::shared_ptr<Glyph> create(char32_t c) const override;
+};