diff --git a/screen_ui.h b/screen_ui.h
index 8987757..de7b644 100644
--- a/screen_ui.h
+++ b/screen_ui.h
@@ -37,16 +37,16 @@
     void SetSystemUpdateText(bool security_update);
 
     // progress indicator
-    void SetProgressType(ProgressType type);
-    void ShowProgress(float portion, float seconds);
-    void SetProgress(float fraction);
+    void SetProgressType(ProgressType type) override;
+    void ShowProgress(float portion, float seconds) override;
+    void SetProgress(float fraction) override;
 
-    void SetStage(int current, int max);
+    void SetStage(int current, int max) override;
 
     // text log
-    void ShowText(bool visible);
-    bool IsTextVisible();
-    bool WasTextEverVisible();
+    void ShowText(bool visible) override;
+    bool IsTextVisible() override;
+    bool WasTextEverVisible() override;
 
     // printing messages
     void Print(const char* fmt, ...) __printflike(2, 3);
@@ -72,8 +72,6 @@
     Icon currentIcon;
 
     const char* locale;
-    bool intro_done;
-    int current_frame;
 
     // The scale factor from dp to pixels. 1.0 for mdpi, 4.0 for xxxhdpi.
     float density_;
@@ -123,8 +121,11 @@
     pthread_t progress_thread_;
 
     // Number of intro frames and loop frames in the animation.
-    int intro_frames;
-    int loop_frames;
+    size_t intro_frames;
+    size_t loop_frames;
+
+    size_t current_frame;
+    bool intro_done;
 
     // Number of frames per sec (default: 30) for both parts of the animation.
     int animation_fps;
@@ -136,11 +137,13 @@
     pthread_mutex_t updateMutex;
     bool rtl_locale;
 
-    void draw_background_locked();
-    void draw_foreground_locked();
-    void draw_screen_locked();
-    void update_screen_locked();
-    void update_progress_locked();
+    virtual void InitTextParams();
+
+    virtual void draw_background_locked();
+    virtual void draw_foreground_locked();
+    virtual void draw_screen_locked();
+    virtual void update_screen_locked();
+    virtual void update_progress_locked();
 
     GRSurface* GetCurrentFrame();
     GRSurface* GetCurrentText();
@@ -148,8 +151,8 @@
     static void* ProgressThreadStartRoutine(void* data);
     void ProgressThreadLoop();
 
-    void ShowFile(FILE*);
-    void PrintV(const char*, bool, va_list);
+    virtual void ShowFile(FILE*);
+    virtual void PrintV(const char*, bool, va_list);
     void PutChar(char);
     void ClearText();
 
@@ -158,9 +161,9 @@
     void LoadLocalizedBitmap(const char* filename, GRSurface** surface);
 
     int PixelsFromDp(int dp);
-    int GetAnimationBaseline();
-    int GetProgressBaseline();
-    int GetTextBaseline();
+    virtual int GetAnimationBaseline();
+    virtual int GetProgressBaseline();
+    virtual int GetTextBaseline();
 
     void DrawHorizontalRule(int* y);
     void DrawTextLine(int x, int* y, const char* line, bool bold);