TempleOSTS_140317.ISO

Demo/Lectures/ScreenMemory.CPP

@@ -0,0 +1,55 @@
+//This just shows how screen memory works.
+//See $LK,"::/Demo/Lectures/MiniGrLib.CPP"$
+
+U0 PlotXY(I64 x,I64 y)
+{
+  //Screen bits are reversed
+  LBts(VGA_GRAPHIC_MEM_BASE,y*GR_WIDTH+x^7);
+}
+
+
+
+U0 Main()
+{
+  I64 i;
+  Bool old_preempt=Preempt(OFF);
+
+//This makes all 4 color planes active.
+  OutU8(VGA_SC_INDEX,VGA_MAP_MASK);
+  OutU8(VGA_SC_DATA,WHITE);
+  MemSet(VGA_GRAPHIC_MEM_BASE,0,GR_WIDTH*GR_HEIGHT/8);
+
+  OutU8(VGA_SC_INDEX,VGA_MAP_MASK);
+  OutU8(VGA_SC_DATA,RED);
+  for (i=0;i<200;i++)
+    PlotXY(i,i);
+
+  OutU8(VGA_SC_INDEX,VGA_MAP_MASK);
+  OutU8(VGA_SC_DATA,GREEN);
+  for (i=0;i<200;i++)
+    PlotXY(100,i);
+
+  OutU8(VGA_SC_INDEX,VGA_MAP_MASK);
+  OutU8(VGA_SC_DATA,BLUE);
+  for (i=0;i<200;i++)
+    PlotXY(200-i,i);
+/*
+If you want a mixed color select multiple planes
+but you have to be sure the unselected planes
+are zero, so select them and make them zero.
+You can't do reads on VGA memory, by the way.
+That means no read-modify-writes, too.
+*/
+  BusyWait(4000000);
+
+  Preempt(old_preempt);
+
+//TempleOS has a 4 plane memory duplicate of the screen, $LK,"gr_screen_image",A="MN:gr_screen_image"$,
+//and only writes actual changes.  See $LK,"GrUpdateVGAGraphics",A="MN:GrUpdateVGAGraphics"$().
+//<CTRL-ALT-F> will flush screen VGA cache.
+  VGAFlush;
+}
+
+Main;
+
+//See $LK,"::/Demo/Lectures/GraphicsCPULoad.CPP"$.