xpgl Lines

To use:

from XPPython3 import xpgl

A line is defined with a start and end point. Polylines are simple a series of connected lines. Each line has:

• Color: a 3-float tuple representing RGB values. You can use Colors for some predefined colors. If a color is not specified, White is used.

• Thickness: a single float representing the (approxiamate) width of the line in texuals. If thickness is not provided, the line will be one textual wide.

• Pattern: a line may be solid, dotted, or a sequence of dot and dashes. Once a pattern is set, it will be use by all lines: it must be reset to solid if desired.

Color and Thickness are settable within each line function call, and do not “carry-over” into subsequent calls. Pattern is only settable using a separate function, and remains set until changed.

drawLine(x1, y1, x2, y2, thickness=1, color=Colors['white']) → None

Parameters

• x1 (float) –

• y1 (float) – Starting (x1, y1) endpoint

• x2 (float) –

• y2 (float) – Ending (x2, y2) endpoint

• thickness (float) – Line width

• color (RGBColor) – OpenGL color. Tuple of floats (r, g, b) ranging [0..1]

Returns

None

Without specifying thickness, this draws a single line of width “1” in given color:

xpgl.drawLine(0, 0, 640, 480, Colors['red'])
xpgl.drawLine(320, 240, 640, 0)

Specifying thickness uses and underlying OpenGL capability:

offset = 0
for i in range(1, 41, 4):
    offset += (2 * i) + 10
    xpgl.drawLine(-50 + offset, 10 , 600 + offset, 400, thickness=i, color=Colors['red'])

drawPolyLine(points, color=Colors['white']) → None:

Parameters

• points (list) – List of vertices (x, y) for the line segments

• thickness (float) – Line width

• color (RGBColor) – OpenGL color. Tuple of floats (r, g, b) ranging [0..1]

Returns

None

Draws a set of line segments from vertex to vertex. Resulting shape does not close unless last vertex is the same as the first. Drawing without specifying thickness:

xpgl.drawPolyLine([(200, 200), (300, 200), (500, 310), (500, 300), (250, 300)])
xpgl.drawPolyLine([(100, 100), (300, 100), (200, 350), (550, 375), (100, 100)], color=Colors['orange'])

Drawing with thickness:

xpgl.drawWidePolyLine([(200, 200), (300, 200), (500, 310), (500, 300), (250, 300)], thickness=3)
xpgl.drawWidePolyLine([(100, 100), (300, 100), (200, 350), (550, 375), (100, 100)], thickness=10, color=Colors['orange'])

setLinePattern(pattern: int = 0xffff) → None

Sets (or removes) stipple pattern associated with all lines. 0xffff disables the pattern, resulting in solid lines.

Stipple pattern is a 16-bit value. Each 1 bit represents “on”, 0 bit represents “off”. Patterns are evaluated low-bit to high-bit (that is right-to-left), and repeat using the 16-bit pattern.

For example:

Pattern	Value in binary	Result
0xffff	1111-1111-1111-1111	“all on”, resulting in solid line
0x5555	0101-0101-0101-0101	“on-off-on-off…”, resulting in a dot pattern, where the dot length is the same as the blank space between to dots.
0x087f	0000-1000-0111-1111	“7 on, four off, 1 on, four off”, yields a dash-dot pattern.

A single pattern is repeated for the length of the line or poly line. If you need a different pattern (different color or different thickness) you’ll need to make a separate function call.:

x1 = 50
x2 = 550
y1 = 100
for pattern in (0xffff, 0x5555, 0x3333, 0x1111, 0x3131, 0x5151, 0x18ff, 0x2727, 0x023f, 0x087f, 0x3f3f, 0x7f7f,  ):
    y2 = y1 = y1 + 15
    xpgl.setLinePattern(pattern)
    xpgl.drawWideLine(x1, y1, x2, y2, thickness=10, color=Colors['orange'])
xpgl.setLinePattern()

Because (typically) your set of drawing functions are called repeatedly, and because a stipple pattern remains active until reset, you should disable the pattern when you are finished. Otherwise, the pattern remains active and on the next call to your function, your lines will continue to use the previous stipple pattern.