DRAWING
Write to the screen
Some time ago there was a question about directly writing to screen memory for high-speed graphics. I don't have the original posting, but little or no discussion resulted.
Here is a "starter" for experimentation with this dangerous but exciting technique. FN SetCPixel acts like PLOT(x,y) but is _very_ much faster. Note that the compatibility of the method with dual monitors, graphics cards etc, is doubtful.
If there are screen-blitter assembly-freaks out there, I would like very much to learn tips and improvements from them.
Robert
DIM gBaseAddr&, gRowBytes%, gHOffset, gVOffset
DIM gScrnBot, gScrnRight, gScrnLineAddr&(1024)
DIM gActualDepth
END GLOBALS
LOCAL FN MicroSeconds&
` dc.w $A193
END FN
' call this before drawing esp if window may have moved
LOCAL FN GetWindowParameters
DIM aPoint.4
gActualDepth=SYSTEM(_crntDepth)
aPoint.h=0: aPoint.v=0
CALL LOCALTOGLOBAL(aPoint)
gHOffset=aPoint.h
gVOffset=aPoint.v
END FN
' call this at start of program
LOCAL FN GetScreenParameters
DIM pmHand&,addr&,j
gScrnBot={REGISTER(a5)+_screenBits+10}
gScrnRight={REGISTER(a5)+_screenBits+12}
pmHand&=[[FN GETMAINDEVICE]+22]
gBaseAddr&=[[pmHand&]]
gRowBytes%={[pmHand&]+4} AND &1FFF
' 1FFF masks off hi bits indicating pixMap type
addr&=gBaseAddr&
FOR j=0 TO gScrnBot
gScrnLineAddr&(j)=addr&
addr&=addr&+gRowBytes%
NEXT j
END FN
LOCAL FN SetCPixel (x,y,pixelByte)
' Fast alternative to MOVETO(x,y): LINE(0,0) toolbox calls
' if monitor is set to 256 colours (depth 8 bits).
' Clipped to screen area
x= x + gHOffset ' to global coord
y =y + gVOffset ' to global coord
LONG IF x>=0
LONG IF x<= gScrnRight
IF y<=gScrnBot THEN POKE gScrnLineAddr&(y)+x,pixelByte
END IF
END IF
END FN
DIM L, micrs&,j
WINDOW 1
FN GetScreenParameters
FN GetWindowParameters
L=150
micrs&=FN MicroSeconds&
FOR j=1 TO L
PLOT 200,j
NEXT j
micrs&=FN MicroSeconds&-micrs&
PRINT@(0,0) "PLOT " micrs&
micrs&=FN MicroSeconds&
FOR j=1 TO L
CALL MOVETO(205,j): CALL LINE (0,0)
NEXT j
micrs&=FN MicroSeconds&-micrs&
PRINT@(0,1) "MOVETO LINE" micrs&"<mu>s"
'not needed here, but a good idea in general..
FN GetWindowParameters
LONG IF gActualDepth=8
micrs&=FN MicroSeconds&
FOR j=1 TO L
FN SetCPixel (210,j,-1)
NEXT j
micrs&=FN MicroSeconds&-micrs&
PRINT@(0,2)"FN SetCPixel" micrs&"<mu>s"
END IF
DO
UNTIL FN BUTTON
Your FN SetCPixel is also much faster than the Toolbox version of SetCPixel. I'm impressed!
Rick