Draw

Statement for sequenced pixel plotting

Syntax
   Draw [target,] cmd

Parameters
   target
      the buffer to draw on
   cmd
      a string containing the sequence of commands

Description
   Drawing will take place onto the current work page set via ScreenSet or 
   onto the target Get/Put buffer if specified.
   The Draw statement can be used to issue several drawing commands all at 
   once; it is useful to quickly draw figures. The command string accepts 
   the following commands:

   Commands to plot pixels:
      +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------+
      |Command|Description                                                                                                                                                   |
      |       |Commands to plot pixels:                                                                                                                                      |
      |B      |Optional prefix: move but do not draw.                                                                                                                        |
      |N      |Optional prefix: draw but do not move.                                                                                                                        |
      |M x,y  |Move to specified screen location. if a '+' or '-' sign precedes x, movement is relative to current cursor position.  x's sign has no effect on the sign of y.|
      |U [n]  |Move n units up. If n is omitted, 1 is assumed.                                                                                                               |
      |D [n]  |Move n units down. If n is omitted, 1 is assumed.                                                                                                             |
      |L [n]  |Move n units left. If n is omitted, 1 is assumed.                                                                                                             |
      |R [n]  |Move n units right. If n is omitted, 1 is assumed.                                                                                                            |
      |E [n]  |Move n units up and right. If n is omitted, 1 is assumed.                                                                                                     |
      |F [n]  |Move n units down and right. If n is omitted, 1 is assumed.                                                                                                   |
      |G [n]  |Move n units down and left. If n is omitted, 1 is assumed.                                                                                                    |
      |H [n]  |Move n units up and left. If n is omitted, 1 is assumed.                                                                                                      |
      |       |Commands to color:                                                                                                                                            |
      |C n    |Changes current foreground color to n.                                                                                                                        |
      |P p,b  |PAINTs (flood fills) region of border color b with color p.                                                                                                   |
      |       |Commands to scale and rotate:                                                                                                                                 |
      |S n    |Sets the current unit length, default is 4.  A unit length of 4 is equal to 1 pixel.                                                                          |
      |A n    |Rotate n*90 degrees (n ranges 0-3).                                                                                                                           |
      |TA n   |Rotate n degrees (n ranges 0-359).                                                                                                                            |
      |       |Extra commands:                                                                                                                                               |
      |X p    |Executes commands at p, where p is a STRING PTR.                                                                                                              |
      +-------+--------------------------------------------------------------------------------------------------------------------------------------------------------------+

   Commands to set the color, size and angle will take affect all 
   subsequent Draw operations.

Draw respects the current clipping region as set by the View (Graphics) 
statement, but its coordinates are not affected by the custom coordinates 
system.

Example
   Screen 13

   'Move to (50,50) without drawing
   Draw "BM 50,50"

   'Set drawing color to 2 (green)
   Draw "C2"

   'Draw a box
   Draw "R50 D30 L50 U30"

   'Move inside the box
   Draw "BM +1,1"

   'Flood fill with color 1 (blue) up to border color 2 
   Draw "P 1,2"

   Sleep

   '' Draws a flower on-screen

   Dim As Integer i, a, c
   Dim As String fill, setangle

   '' pattern for each petal
   Dim As Const String petal = _
      _
      ("X" & VarPtr(setangle)) _ '' link to angle-setting string
      _
      & "C15" _       '' set outline color (white)
      & "M+100,+10" _ '' draw outline
      "M +15,-10" _
      "M -15,-10" _
      "M-100,+10" _
      _
      & "BM+100,0" _              '' move inside petal
      & ("X" & VarPtr(fill)) _    '' flood-fill petal (by linking to fill string)
      & "BM-100,0"                '' move back out

   '' set screen
   ScreenRes 320, 240, 8

   '' move to center
   Draw "BM 160, 120"

   '' set initial angle and color number
   a = 0: c = 32

   For i = 1 To 24

      '' make angle-setting and filling command strings
      setangle = "TA" & a
      fill = "P" & c & ",15"

      '' draw the petal pattern, which links to angle-setting and filling strings
      Draw petal
      
      '' short delay
      Sleep 100

      '' increment angle and color number
      a += 15: c += 1

   Next i

   Sleep

Differences from QB
   * target is new to FreeBASIC
   * QB used the special pointer keyword VARPTR$ with the X p command.
   * FB does not currently allow sub-pixel movements: all movements are 
     rounded to the nearest integer coordinate.

See also
   * Draw String
   * Screen (Graphics)
   * VarPtr
   * Paint

