Chapter 4

Drawing Commands

All drawing commands relate to an invisible point of reference

on the screen called the draw pointer. Originally, the draw

pointer is at position 0,0. You can change the position by using

the SetDPtr and RSetDPtr commands described in this chapter.

In addition, some draw commands automatically update the

draw pointer. For example, the LineM command draws a line

from the current draw pointer position to the specified end coor

dinates and moves the draw pointer to those end coordinates.

The Line command draws a line but does not move the pointer.

Also, note that all draw commands are affected by the pattern

and logic commands described in Chapter 3.

Do not confuse the draw pointer with the graphics cursor. The

graphics cursor is the graphic representation of the mouse/joy

stick position on the screen.

In this chapter, commands that use relative coordinates (offsets)

are listed with their counterparts that use absolute coordinates.

For example, RSetDPtr is listed under SetDPtr.,

Function: Draws an arc with its midpoint at the current draw

pointer position. You specify the curve by both the X and Y

dimensions, as you do an ellipse. In this way, you can draw

either elliptical or circular arcs. The arc is clipped by a line

defined by the (XO1,Y01) - (X02,Y02) coordinates. These coor

dinates are signed 16 bit values and are relative to the center

of the ellipse. The draw pointer remains in its original

position.

Parameters: HBRx LBRx HBRy LBRy HX01 LX01 HY01

LY01 HX02 LX02 HY02 LY02

Notes:

The resulting arc depends on the order in which you specify

the line coordinates. Arc3P first draws the line from Point

1 to Point 2 and then draws the ellipse in a clockwise

direction.

The coordinates of the screen are as follows:

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Drawing Commands l 4

Function: Draws and fills a rectangle that is defined by the

diagonal line from the current draw pointer position to the

specified position. The box is drawn in the current foreground

color. The draw pointer returns to its original location.

Function: Draws and fills a rectangle that is defined by the

diagonal line from the current draw pointer position to the

point specified by the offsets. The box is drawn in the current

foreground color. The draw pointer returns to its original loca

tion. This is a relative command.

HBXo LBXo HBYo LBYo

Draw Box

HBXo LBXo HBYo LBYo

Drawing Commands l 4

Circle Draw Circle

Function: Draws a circle of the specified radius with the cen
ter of the circle at the current draw pointer position. The cir
cle is drawn in the current foreground color. The draw pointer
remains in its original location.

Code: 1B 50

Parameters: HBR LBR

r

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OS-9 Windowing System

Ellipse Draw Ellipse

Function: Draws an ellipse with its center at the current draw
pointer position. The X value specifies the horizontal radius,
and the Y value specifies the vertical radius. The ellipse is
drawn in the current foreground color. The draw pointer
remains in its original location. This is a relative command.

Code: 1B 51

Parameters: HBRx LBRx HBRy LBRy

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Drawing Commands l 4

FFiII Flood Fill

Function: Fills the area where the background is the same
color as the draw pointer. Filling starts at the current draw
pointer position, using the current foreground color. The draw
pointer returns to its original location. This is a relative
command.

Code: 1B 4F

Parameters: None

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OS-9 Windowing System

Line Draw Line

Function: Draws a line from the current draw pointer position
to the specified point, using the current foreground color. The
draw pointer returns to its original location.

Code: 1B 44

Parameters: HBX LBX HBY LBY

RLineRelative Draw Line

Function: Draws a line from the current draw pointer position
to the point specified by the x,y offsets, using the current fore
ground color. The draw pointer returns to its original location.
This is a relative command.

Code: 1B 45

Parameters: HBXo LBXo HBYo LBYo

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Drawing Commands / 4

Line M Draw Line and Move

Function: Draws a line from the current draw pointer position

to the specified point, using the current foreground color. The

draw pointer stays at the new location.

Code: 1B 46

Parameters: HBX LBX HBY LBY

RLineMRelative Draw Line and Move

Function: Draws a line from the current draw pointer position

to the point specified by the offsets, using the current fore

ground color. The draw pointer stays at the new location. This

is a relative command.

'' Code: 1B 47

Parameters: HBXo LBXo HBYo LBYo

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OS-9 Windowing System

Point Draw Point

Function: Draws a pixel at the specified coordinates, using

the current foreground color.

Code: 1B 42
Parameters: HBX LBX HBY LBY

RPointRelative Draw Point

Function: Draws a pixel at the location specified by the off
sets, using the current foreground color. This is a relative
command.
Code: 1B 43
Parameters: HBXo LBXo HBYo LBYo

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Drawing Commands / 4

PutGCPut Graphics Cursor

Function: Puts and displays the graphics cursor at the speci
fied location. The coordinates passed to this command are not
window
relative. The horizontal range is 0 to 639. The vertical range
is 0 to 191. The default position is 0,0.

This command is useful for applications running under GrfTnt
so that you can display a graphics cursor under WindInt even
if you don't want mouse control of the cursor.

Code: iB 4E

Parameters: HBX LBX HBY LBY

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OS-9 Windowing System

SetDPtrSet Draw Pointer

Function: Sets the draw pointer to the specified coordinates.

The new draw pointer position is used as the beginning point

in the next draw command if other coordinates are not

specified.

Code: 1B 40

Parameters: HBX LBX HBY LBY

RSetDPtrRelative Set Draw Pointer

Function: Sets the draw pointer to the point specified by the

offsets. The new draw pointer position is used as the begin

ning point in the next draw command if other coordinates are

not specified. This is a relative command.

Code: iB 41
Parameters: HBXo LBXo HBYo LBYo

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