Dynamic adjustment of the terminal refresh rate between 5 and 60 Hz

ChangeLog

@@ -1,4 +1,8 @@
-2021-02-09 Markus Gans  <guru.mail@muenster.de>
+2021-03-15 Markus Gans  <guru.mail@muenster.de>
+	* Dynamic adjustment of the terminal refresh rate between 
+	  5 and 60 Hz
+
+2021-03-09 Markus Gans  <guru.mail@muenster.de>
 	* Implementation of an own padding print method for sending 
 	  control codes to the terminal
 

src/fkeyboard.cpp

@@ -153,9 +153,7 @@ bool FKeyboard::isKeyPressed (uInt64 blocking_time)
     && select(stdin_no + 1, &ifds, nullptr, nullptr, &tv) > 0
     && FD_ISSET(stdin_no, &ifds) )
   {
-    has_pending_input = true;
+    return (has_pending_input = true);
-    FD_CLR (stdin_no, &ifds);
-    tv.tv_sec = 0;
   }
 
   if ( isKeypressTimeout() || ! non_blocking_input_support )

src/ftermcap.cpp

@@ -438,7 +438,6 @@ std::string FTermcap::encodeParams ( const std::string& cap
 //----------------------------------------------------------------------
 void FTermcap::delay_output (int ms, const defaultPutChar& outc)
 {
-
   if ( no_padding_char )
   {
     std::this_thread::sleep_for(std::chrono::milliseconds(ms));

src/fvterm.cpp

@@ -60,7 +60,9 @@ bool                 FVTerm::combined_char_support{false};
 bool                 FVTerm::no_terminal_updates{false};
 bool                 FVTerm::cursor_hideable{false};
 bool                 FVTerm::force_terminal_update{false};
-uInt64               FVTerm::flush_wait{16667};  // 16.6 ms  (60 Hz)
+uInt64               FVTerm::flush_wait{MIN_FLUSH_WAIT};
+uInt64               FVTerm::flush_average{MIN_FLUSH_WAIT};
+uInt64               FVTerm::flush_median{MIN_FLUSH_WAIT};
 uInt64               FVTerm::term_size_check_timeout{500000};  // 500 ms
 uInt                 FVTerm::erase_char_length{};
 uInt                 FVTerm::repeat_char_length{};
@@ -573,6 +575,8 @@ void FVTerm::flush() const
 {
   // Flush the output buffer
 
+  flushTimeAdjustment();
+
   if ( ! output_buffer || output_buffer->empty()
     || ! (isFlushTimeout() || force_terminal_update) )
     return;
@@ -2888,6 +2892,52 @@ inline bool FVTerm::isTermSizeChanged() const
   return false;
 }
 
+//----------------------------------------------------------------------
+inline void FVTerm::flushTimeAdjustment() const
+{
+  timeval now;
+  FObject::getCurrentTime(&now);
+  timeval diff = now - time_last_flush;
+
+  if ( diff.tv_sec > 0 || diff.tv_usec > 400000 )
+  {
+    flush_wait = MIN_FLUSH_WAIT;  // Reset to minimum values after 400 ms
+    flush_average = MIN_FLUSH_WAIT;
+    flush_median = MIN_FLUSH_WAIT;
+  }
+  else
+  {
+    uInt64 usec = diff.tv_usec;
+
+    if ( usec < MIN_FLUSH_WAIT )
+      usec = MIN_FLUSH_WAIT;
+    else if ( usec > MAX_FLUSH_WAIT )
+      usec = MAX_FLUSH_WAIT;
+
+    if ( usec >= flush_average )
+      flush_average += (usec - flush_average) / 10;
+    else
+    {
+      uInt64 delta = (flush_average - usec) / 10;
+
+      if ( flush_average >= delta )  // Avoid uInt64 underflow
+        flush_average -= delta;
+    }
+
+    if ( usec >= flush_median )
+      flush_median += flush_average / 5;
+    else
+    {
+      uInt64 delta = flush_average / 5;
+
+      if ( flush_median >= delta )  // Avoid uInt64 underflow
+        flush_median -= delta;
+    }
+
+    flush_wait = flush_median;
+  }
+}
+
 //----------------------------------------------------------------------
 inline bool FVTerm::isFlushTimeout()
 {

src/include/final/fvterm.h

@@ -345,6 +345,9 @@ class FVTerm
     // Constants
     //   Buffer limit for character output on the terminal
     static constexpr std::size_t TERMINAL_OUTPUT_BUFFER_LIMIT = 1024;
+    //   Upper and lower flush limit
+    static constexpr uInt64 MIN_FLUSH_WAIT = 16667;   //   16.6 ms = 60 Hz
+    static constexpr uInt64 MAX_FLUSH_WAIT = 200000;  //  200.0 ms = 5 Hz
 
     // Methods
     void                  resetTextAreaToDefault ( const FTermArea*
@@ -412,6 +415,7 @@ class FVTerm
     bool                  updateTerminalCursor() const;
     bool                  isInsideTerminal (const FPoint&) const;
     bool                  isTermSizeChanged() const;
+    void                  flushTimeAdjustment() const;
     static bool           isFlushTimeout();
     static bool           isTermSizeCheckTimeout();
     static bool           hasPendingUpdates (const FTermArea*);
@@ -451,6 +455,8 @@ class FVTerm
     static bool                   no_terminal_updates;
     static bool                   force_terminal_update;
     static uInt64                 flush_wait;
+    static uInt64                 flush_average;
+    static uInt64                 flush_median;
     static uInt64                 term_size_check_timeout;
     static uInt                   erase_char_length;
     static uInt                   repeat_char_length;

test/ftermcap-test.cpp

@@ -276,6 +276,13 @@ void FTermcapTest::paddingPrintTest()
   CPPUNIT_ASSERT ( ! output.empty() );
   CPPUNIT_ASSERT ( output == "12$3$<4567" );
 
+  // Without a digit
+  output.clear();
+  status = tcap.paddingPrint ("12$3$<x>4567", 1, FTermcapTest::putchar_test);
+  CPPUNIT_ASSERT ( status == finalcut::FTermcap::Status::OK );
+  CPPUNIT_ASSERT ( ! output.empty() );
+  CPPUNIT_ASSERT ( output == "12$3$<x>4567" );
+
   // With 2 ms print delay
   output.clear();
   auto start = high_resolution_clock::now();