added doublebuffering to monogfx (in both lores and hires mode)

compiler/res/prog8lib/cx16/monogfx.p8

@@ -22,18 +22,23 @@ monogfx {
     const ubyte MODE_STIPPLE = %00000001
     const ubyte MODE_INVERT  = %00000010
 
+    uword buffer_visible, buffer_back
+
+
     sub lores() {
         ; enable 320*240 bitmap mode
+        buffer_visible = buffer_back = $0000
         cx16.VERA_CTRL=0
         cx16.VERA_DC_VIDEO = (cx16.VERA_DC_VIDEO & %11001111) | %00100000      ; enable only layer 1
         cx16.VERA_DC_HSCALE = 64
         cx16.VERA_DC_VSCALE = 64
         cx16.VERA_L1_CONFIG = %00000100
         cx16.VERA_L1_MAPBASE = 0
-        cx16.VERA_L1_TILEBASE = 0
+        cx16.VERA_L1_TILEBASE = 0           ; lores
         width = 320
         height = 240
         lores_mode = true
+        buffer_visible = buffer_back = $0000
         mode = MODE_NORMAL
         clear_screen(false)
     }
@@ -46,14 +51,40 @@ monogfx {
         cx16.VERA_DC_VSCALE = 128
         cx16.VERA_L1_CONFIG = %00000100
         cx16.VERA_L1_MAPBASE = 0
-        cx16.VERA_L1_TILEBASE = %00000001
+        cx16.VERA_L1_TILEBASE = %00000001       ; hires
         width = 640
         height = 480
         lores_mode = false
+        buffer_visible = buffer_back = $0000
         mode = MODE_NORMAL
         clear_screen(false)
     }
 
+    sub enable_doublebuffer() {
+        ; enable double buffering mode
+        if lores_mode {
+            buffer_visible = $0000
+            buffer_back = $2800
+        } else {
+            buffer_visible = $0000
+            buffer_back = $9800
+        }
+    }
+
+    sub swap_buffers(bool wait_for_vsync) {
+        ; flip the buffers: make the back buffer visible and the other one now the backbuffer.
+        ; to avoid any screen tearing it is advised to call this during the vertical blank (pass true)
+        if wait_for_vsync
+            sys.waitvsync()
+        cx16.r0 = buffer_back
+        buffer_back = buffer_visible
+        buffer_visible = cx16.r0
+        cx16.VERA_CTRL = 0
+        cx16.r0 &= %1111110000000000
+        cx16.VERA_L1_TILEBASE = cx16.VERA_L1_TILEBASE & 1 | (cx16.r0H >>1 )
+    }
+
+
     sub textmode() {
         ; back to normal text mode
         cx16.r15L = cx16.VERA_DC_VIDEO & %00000111 ; retain chroma + output mode
@@ -559,6 +590,7 @@ drawmode:               ora  cx16.r15L
     sub disc(uword @zp xcenter, uword @zp ycenter, ubyte @zp radius, bool draw) {
         ; Warning: NO BOUNDS CHECKS. Make sure circle fits in the screen.
         ; Midpoint algorithm, filled
+        ; Note: has problems with INVERT draw mode because of horizontal span overdrawing. Horizontal lines may occur.
         if radius==0
             return
         ubyte @zp yy = 0
@@ -597,6 +629,7 @@ drawmode:               ora  cx16.r15L
     sub safe_disc(uword @zp xcenter, uword @zp ycenter, ubyte @zp radius, bool draw) {
         ; Does bounds checking and clipping.
         ; Midpoint algorithm, filled
+        ; Note: has problems with INVERT draw mode because of horizontal span overdrawing. Horizontal lines may occur.
         if radius==0
             return
         ubyte @zp yy = 0
@@ -696,7 +729,7 @@ invert:
                     adc  p8v_times40_lsb,y
                     sta  cx16.VERA_ADDR_L
                     lda  p8v_times40_msb,y
-                    adc  #0
+                    adc  p8v_buffer_back+1
                     sta  cx16.VERA_ADDR_M
 
                     lda  p8v_xx
@@ -708,7 +741,6 @@ invert:
                 ; width=640 (hires)
                 %asm {{
                     stz  cx16.VERA_CTRL
-                    stz  cx16.VERA_ADDR_H
                     lda  p8v_xx
                     and  #7
                     pha     ; xbits
@@ -723,10 +755,15 @@ invert:
                 ;xx /= 8
                 xx += yy*(640/8)
                 %asm {{
-                    lda  p8v_xx+1
-                    sta  cx16.VERA_ADDR_M
                     lda  p8v_xx
                     sta  cx16.VERA_ADDR_L
+                    lda  p8v_xx+1
+                    clc
+                    adc  p8v_buffer_back+1
+                    sta  cx16.VERA_ADDR_M
+                    lda  #0
+                    rol  a   ; hi bit carry also needed when double-buffering
+                    sta  cx16.VERA_ADDR_H
                     plx     ; xbits
                     lda  p8v_maskbits,x
                 }}
@@ -768,11 +805,15 @@ invert:
 
         %asm {{
             stz  cx16.VERA_CTRL
-            stz  cx16.VERA_ADDR_H
-            lda  p8v_xx+1
-            sta  cx16.VERA_ADDR_M
             lda  p8v_xx
             sta  cx16.VERA_ADDR_L
+            lda  p8v_xx+1
+            clc
+            adc  p8v_buffer_back+1
+            sta  cx16.VERA_ADDR_M
+            lda  #0
+            rol  a   ; hi bit carry also needed when double-buffering
+            sta  cx16.VERA_ADDR_H
             ply         ; xbits
             lda  p8s_plot.p8v_maskbits,y
             and  cx16.VERA_DATA0
@@ -855,8 +896,8 @@ skip:
         }
 
         sub fill_scanline_right() {
-             ; TODO maybe this could use vera auto increment, but that requires some clever masking calculations
+            ; TODO maybe this could use vera auto increment, but that requires some clever masking calculations
-             cx16.r9s = xx
+            cx16.r9s = xx
             while xx <= width-1 {
                 if pgetset()
                     break
@@ -891,11 +932,15 @@ skip:
 
             %asm {{
                 stz  cx16.VERA_CTRL
-                stz  cx16.VERA_ADDR_H
-                lda  p8v_xpos+1
-                sta  cx16.VERA_ADDR_M
                 lda  p8v_xpos
                 sta  cx16.VERA_ADDR_L
+                lda  p8v_xpos+1
+                clc
+                adc  p8v_buffer_back+1
+                sta  cx16.VERA_ADDR_M
+                lda  #0
+                rol  a   ; hi bit carry also needed when double-buffering
+                sta  cx16.VERA_ADDR_H
                 ply         ; xbits
                 lda  p8s_plot.p8v_maskbits,y
                 and  cx16.VERA_DATA0
@@ -942,12 +987,12 @@ _doplot         beq  +
                 ror  a
                 lsr  a
                 lsr  a
-                clc
                 ldy  p8v_yy
+                clc
                 adc  p8v_times40_lsb,y
                 sta  cx16.VERA_ADDR_L
                 lda  p8v_times40_msb,y
-                adc  #0
+                adc  p8v_buffer_back+1
                 sta  cx16.VERA_ADDR_M
                 lda  #%00010000     ; autoincr
                 sta  cx16.VERA_ADDR_H
@@ -975,8 +1020,11 @@ _doplot         beq  +
                 lda  cx16.r0L
                 sta  cx16.VERA_ADDR_L
                 lda  cx16.r0H
+                clc
+                adc  p8v_buffer_back+1
                 sta  cx16.VERA_ADDR_M
-                lda  #%00010000     ; autoincr
+                lda  #%00001000     ; autoincr (1 bit shifted)
+                rol  a              ; hi bit carry also needed when double-buffering
                 sta  cx16.VERA_ADDR_H
             }}
         }
@@ -1146,15 +1194,11 @@ cdraw_mod2              ora  cx16.VERA_DATA1
             cmp  #0
             beq  +
             lda  #255
-+           ldy  #80
++           ldy  #40
--           sta  cx16.VERA_DATA0
+-
-            sta  cx16.VERA_DATA0
+            .rept  16
-            sta  cx16.VERA_DATA0
-            sta  cx16.VERA_DATA0
-            sta  cx16.VERA_DATA0
-            sta  cx16.VERA_DATA0
-            sta  cx16.VERA_DATA0
             sta  cx16.VERA_DATA0
+            .endrept
             dey
             bne  -
             rts

docs/source/libraries.rst

@@ -816,6 +816,7 @@ Full-screen lores or hires monochrome bitmap graphics routines, available on the
 - two resolutions: lores 320*240 or hires 640*480 bitmap mode
 - optimized routines for monochrome (2-color) graphics
 - clearing screen, switching screen mode, also back to text mode
+- doublebuffering option to avoid flicker
 - drawing and reading individual pixels
 - drawing lines, rectangles, filled rectangles, circles, discs
 - flood fill
@@ -823,7 +824,7 @@ Full-screen lores or hires monochrome bitmap graphics routines, available on the
 - can draw using a stipple pattern (alternate black/white pixels) and in invert mode (toggle pixels)
 
 Read the `monogfx source code <https://github.com/irmen/prog8/tree/master/compiler/res/prog8lib/cx16/monogfx.p8>`_
-to see what's in there.
+and the `testmonogfx` example program, to see what's in there.
 
 
 palette  (cx16 only)

docs/source/todo.rst

@@ -1,6 +1,9 @@
 TODO
 ====
 
+Bug: monogfx circle, plot and line drawing with INVERT mode is broken (garbage pixels)
+
+
 STRUCTS: are being developed in their own separate branch for now, called "structs".
 Idea is to make it feature complete in the IR/Virtual target, then merge it to master?, and then start building the 6502 code generation for it.
 

examples/cx16/testmonogfx.p8

@@ -1,6 +1,6 @@
 %import monogfx
-%import textio
 %import math
+%import conv
 
 %option no_sysinit
 %zeropage basicsafe
@@ -18,8 +18,7 @@ main {
         sys.wait(2*60)
         demo2()
 
-        monogfx.textmode()
+        doublebuffer.demo()
-        txt.print("done!\n")
     }
 
     sub demofill() {
@@ -214,3 +213,40 @@ main {
 
     }
 }
+
+
+
+
+doublebuffer {
+    sub demo() {
+        monogfx.lores()
+        monogfx.text_charset(1)
+        monogfx.enable_doublebuffer()
+        uword cx = 100
+
+        repeat {
+            monogfx.clear_screen(false)
+            monogfx.text(50, 10, true, iso:"Double Buffered")
+            monogfx.circle(160, 120, 100, true)
+            monogfx.disc(160, 120, 40, true)
+
+            monogfx.rect(40, 40, 240, 180, true)
+            monogfx.drawmode(monogfx.MODE_STIPPLE)
+            monogfx.fill(50, 50, true, 1)
+
+            monogfx.drawmode(monogfx.MODE_NORMAL)
+            monogfx.fill(250, 50, true, 1)
+            monogfx.fillrect( 10, 50, 20, 100, true)
+            monogfx.line(10, 10, 300, 200, true)
+
+            repeat 200 {
+                monogfx.plot($00e0 + math.randrange(64), 20 + math.randrange(20), true)
+            }
+
+            monogfx.circle(cx, 219, 20, true)
+            monogfx.text(cx+20, 225, true, conv.str_uw(cx))
+            cx++
+            monogfx.swap_buffers()
+        }
+    }
+}

examples/test.p8

@@ -1,58 +1,21 @@
-%import textio
+%import math
-%zeropage basicsafe
+%import monogfx
-
 
 main {
     sub start() {
-        word w1, w2, w3, w4
+        monogfx.hires()
-        uword uw1, uw2, uw3
+        monogfx.fillrect(100, 100, 200, 100, true)
 
-        w1 = -111
+        sys.wait(60)
-        w2 = 222
-        w3 = -333
-        w4 = -20
 
-        uw1 = 111
+        monogfx.drawmode(monogfx.MODE_INVERT)
-        uw2 = 222
+        monogfx.circle(150, 120, 80, true)           ; TODO INVERT is BROKEN
-        uw3 = 333
+        monogfx.line(10, 20, 250, 160, true)        ; TODO INVERT is BROKEN
 
-        txt.print_w(w2*w3)
+        repeat 500 {
-        txt.spc()
+            monogfx.plot( math.rnd(), math.rnd(), true)     ; TODO INVERT is BROKEN
-        w1 = w2 * w3
+        }
-        txt.print_w(w1)
-        txt.nl()
-        txt.print_w(w3*w4)
-        txt.nl()
 
-        txt.print_uw(uw2*uw3)
+        repeat  {}
-        txt.spc()
-        uw1 = uw2 * uw3
-        txt.print_uw(uw1)
-        txt.nl()
-        txt.nl()
-
-
-        w1 = -111
-        w2 = 22222
-        w3 = -333
-        w4 = -17
-
-        uw1 = 111
-        uw2 = 22222
-        uw3 = 333
-
-        txt.print_w(w2/w3)
-        txt.spc()
-        w1 = w2 / w3
-        txt.print_w(w1)
-        txt.nl()
-        txt.print_w(w3/w4)
-        txt.nl()
-
-        txt.print_uw(uw2/uw3)
-        txt.spc()
-        uw1 = uw2 / uw3
-        txt.print_uw(uw1)
-        txt.nl()
     }
 }