add draw-v-line

one_line_canvas.tal

@@ -16,8 +16,35 @@
 	setup-gui
 	#58 #58 #1f draw-h-line
 	#58 #58 #1f #02 MUL  draw-h-line
+	#1f #58 #1f  draw-v-line
+	#1f #02 #58 MUL #1f  draw-v-line
 	BRK
 
+@draw-v-line ( l x y )
+    SWP ( l y x )
+    #00 ( l y x 00 )
+    SWP .Screen/x DEO2 ( l y )
+    ( store vars )
+    !{ &y $1 &l $1 }
+    ,/y STR ,/l STR
+
+    &loop
+        ( set y )
+        ,/y LDR DUP ( y y )
+        #00 SWP ( y 00 y)
+        .Screen/y DEO2 ( y )
+        ( draw pixel )
+        PX
+        ( incrment y )
+        INC ( y+1 )
+        ,/y STR ( )
+        ( decrement l )
+        ,/l LDR #01 ( l 01 )
+        SUB ( l-1 )
+        ,/l STRk POP ( l )
+        #00 NEQ ?&loop
+	JMP2r
+
 @draw-h-line ( l x y )
     #00 ( l x y 00 )
     SWP .Screen/y DEO2 ( l x )