save pixels of drawing to ordered list

one_line_canvas.tal

@@ -30,6 +30,8 @@
 	.canvas-height #01 ADD .canvas-width #01 SUB .canvas-height  draw-v-line
 	( right line )
 	.canvas-height #01 ADD .canvas-width #02 MUL #01 ADD .canvas-height draw-v-line
+	( set pxs-pt to start of pixels )
+	;pxs ;pxs-pt STA2
 	;on-mouse .Mouse/vector DEO2
 	BRK
 
@@ -47,6 +49,33 @@
     .x LDZ2 .Screen/x DEO2
 	.y LDZ2 .Screen/y DEO2
 	#01 .Screen/pixel DEO
+    ( set local pt to start of pixels )
+    !{ &local-pt $2 }
+    ;pxs ,/local-pt STR2
+    &loop
+        ( is the drawing done? )
+        ;pxs-pt LDA2 ( pt* )
+        ;pxs #1550 ADD2 ( pt* end-of-px* )
+        EQU2 ?/end
+        ( check if current xy has already been visited )
+        ,/local-pt LDR2 LDA2 ( x1 y1 )
+        .x LDZ2 NIP ( x1 y1 x )
+        .y LDZ2 NIP ( x1 y1 x y )
+        EQU2 ?/end
+        ( have we go through the whole list? )
+        ,/local-pt LDR2 ( local-pt* )
+        ;pxs #1550 ADD2 ( local-pt* end-of-px* )
+        EQU2 ?/save
+        ( incrment pxs pointer and save it )
+        ,/local-pt LDR2 ( local-pt* )
+        #0002 ADD2 ( local-pt*+2 )
+        ,/local-pt STR2
+        !&loop
+    &save
+    .x LDZ2 NIP .y LDZ2 NIP ( x y )
+    ;pxs-pt LDA2 ( x y pt* )
+    STA2
+    ;pxs-pt LDA2 INC2 INC2 ;pxs-pt STA2
 	&end
 	JMP2r
 
@@ -141,3 +170,13 @@
 . . . . . . . . 3c
 . . . . . . . . 18
 )
+
+@pxs-pt $2
+@pxs $1550 ( 5456 )
+(
+    pxs are the pixels of the drawing in order they are drawn
+    0001 05 <-- x1
+    0002 04 <-- y1
+    0003 05 <-- x2
+    0004 03 <-- y2
+)