Increment screen update to make it easier to detect changes

If multiple consumers need to check if the screen has changed, a simple flag
does not do it. Instead, increment a counter that each client will be able to
check indepdendently.

This will be useful for an upcoming test framework

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

sim/dmcp.cpp

@@ -54,7 +54,7 @@ RECORDER(lcd_warning,   64, "Warnings from lcd/display functions");
 
 #undef ppgm_fp
 
-volatile int lcd_needsupdate = 1;
+volatile int lcd_needsupdate = 0;
 int lcd_buf_cleared = 0;
 uint8_t lcd_buffer[LCD_SCANLINE * LCD_H / 8];
 
@@ -113,6 +113,12 @@ int key_empty()
 {
     return keyrd == keywr;
 }
+
+int key_remaining()
+{
+    return nkeys - (keywr - keyrd);
+}
+
 int key_pop()
 {
     if (keyrd != keywr)
@@ -332,27 +338,27 @@ void lcd_print(disp_stat_t * ds, const char* fmt, ...)
 void lcd_forced_refresh()
 {
     record(lcd, "Forced refresh");
-    lcd_needsupdate = 1;
+    lcd_needsupdate++;
 }
 void lcd_refresh()
 {
     record(lcd, "Refresh");
-    lcd_needsupdate = 1;
+    lcd_needsupdate++;
 }
 void lcd_refresh_dma()
 {
     record(lcd, "Refresh DMA");
-    lcd_needsupdate = 1;
+    lcd_needsupdate++;
 }
 void lcd_refresh_wait()
 {
     record(lcd, "Refresh Wait");
-    lcd_needsupdate = 1;
+    lcd_needsupdate++;
 }
 void lcd_refresh_lines(int ln, int cnt)
 {
     record(lcd, "Refresh lines (%d-%d) count %d", ln, ln+cnt-1, cnt);
-    lcd_needsupdate = ln >= 0 && cnt > 0;
+    lcd_needsupdate += (ln >= 0 && cnt > 0);
 }
 void lcd_setLine(disp_stat_t * ds, int ln_nr)
 {

sim/sim-screen.cpp

@@ -112,9 +112,9 @@ void Screen::update()
 //   Refresh the screen
 // ----------------------------------------------------------------------------
 {
-    if (lcd_needsupdate)
+    if (lcd_needsupdate != lcd_update)
     {
-        lcd_needsupdate = 0;
+        lcd_update = lcd_needsupdate;
     }
     else
     {
@@ -139,7 +139,6 @@ void Screen::update()
     }
     pt.end();
 
-
     mainScreen->setPixmap(mainPixmap);
     QGraphicsView::update();
     screenTimer.setSingleShot(true);

sim/sim-screen.h

@@ -59,6 +59,8 @@ public:
     QGraphicsPixmapItem *mainScreen;
     QPixmap              mainPixmap;
 
+    int                  lcd_update;
+
   public:
     explicit Screen(QWidget *parent = 0);
     ~Screen();