diff --git a/library/graphics/hwlib-graphics-window.hpp b/library/graphics/hwlib-graphics-window.hpp
index d04ca8b..b6eebb1 100644
--- a/library/graphics/hwlib-graphics-window.hpp
+++ b/library/graphics/hwlib-graphics-window.hpp
@@ -46,7 +46,7 @@ class window : public noncopyable {
    /// The default implementation writes to all pixels in sequence.
    /// A concrete window can provide a faster implementation.       
    virtual void clear_implementation( 
-      color col
+      color col = unspecified
    ){ 
       for( const auto p : all( size ) ){
          write_implementation( p, col.specify( background ) );    
@@ -87,7 +87,7 @@ class window : public noncopyable {
       size{ size }, 
       background{ background }, 
       foreground{ foreground }
-   { clear( background ); }
+   {}
    
    /// write a pixel
    /// 
diff --git a/library/peripherals/hwlib-glcd-oled.hpp b/library/peripherals/hwlib-glcd-oled.hpp
index 541c84c..9e28f79 100644
--- a/library/peripherals/hwlib-glcd-oled.hpp
+++ b/library/peripherals/hwlib-glcd-oled.hpp
@@ -330,6 +330,7 @@ class glcd_oled_i2c_128x64_direct : public ssd1306_i2c, public window {
          ssd1306_initialization, 
          sizeof( ssd1306_initialization ) / sizeof( uint8_t ) 
       );     
+      clear();      
    }
    
    void flush() override {}  
@@ -394,7 +395,7 @@ class glcd_oled_spi_128x64_direct_res_dc_cs :
       command( ssd1306_commands::display_all_on_resume );  
       command( ssd1306_commands::normal_display );
       command( ssd1306_commands::display_on );
-      
+      clear();      
    }
    
    void clear_implementation(  color c ) override {
@@ -454,6 +455,7 @@ class glcd_oled_i2c_128x64_buffered : public ssd1306_i2c, public window {
          ssd1306_initialization, 
          sizeof( ssd1306_initialization ) / sizeof( uint8_t ) 
       );  
+      clear();      
    }
    
    void flush() override {
@@ -527,6 +529,7 @@ class glcd_oled_i2c_128x64_fast_buffered : public ssd1306_i2c, public window {
          ssd1306_initialization, 
          sizeof( ssd1306_initialization ) / sizeof( uint8_t ) 
       );     
+      clear();
    }
    
    void flush() override {
diff --git a/library/peripherals/hwlib-glcd-st7789.hpp b/library/peripherals/hwlib-glcd-st7789.hpp
index 40824db..57349bc 100644
--- a/library/peripherals/hwlib-glcd-st7789.hpp
+++ b/library/peripherals/hwlib-glcd-st7789.hpp
@@ -179,6 +179,8 @@ class st7789_spi_dc_cs_rst : public st7789, public window {
       wait_ms( 100 );
       command( commands::DISPON );
       wait_ms( 100 );
+      
+      clear();      
    }     
 
    void flush() override {