Simple Graphical Objects
Simple GLG graphical objects can be directly viewed in a drawing. These are the simplest building blocks of a picture, and most of them will seem familiar to you. The following sections introduce the GLG objects in greater depth, and provide lists of the most commonly accessed object attributes.
Polygon
The polygon is a basic graphical object, and is used to represent both lines and polygons. A line in a GLG drawing is simply an open polygon, while most shapes are represented by closed polygons of one sort or another. A straight line is a two-point polygon.
The polygon is basic to the structure of a GLG drawing in other ways. Arcs, parallelograms, splines and connectors inherit their attributes from a polygon.
A simple polygon has a control point at each vertex. It also has the following attributes:
FillColor
The color of the polygon's interior, if it is filled.
EdgeColor
The color of the polygon's defining line or edge.
LineWidth
The thickness of a polygon's edge. Lines with odd line width use round line ends. Lines with an even line width use square ends. The intermediate connections of a multi-line polygon always use rounded connections.
LineType
The line pattern (solid, dashed, etc.) for rendering the edge of the polygon.
FillType
Defines how polygon is rendered. Possible choices are GLG_FILL, GLG_EDGE and GLG_FILL_AND_EDGE.
OpenType
Defines whether or not the line connecting the first and the last points of the polygon is drawn. It does not have any effect on polygons with fewer than three points.
Shading
Disables shading for an individual polygon. Shading is enabled for the viewport if it has a light object added to it.
AntiAliasing
Controls antialiasing of the polygon's edges and may have the following values:
Inherit antialiasing settings from the global setting, which is GLG_ANTI_ALIASING_INT by default.
Enable antialiasing and map vertices to integer pixel boundaries. This matches the coordinate mapping of the native non-OpenGL renderer and makes the straight lines look sharper.
Enables antialiasing and uses double vertex coordinates. This setting makes the curved lines look better. It is used as a default setting for arcs and spline objects.
The antialiasing is enabled only for the viewports that use the OpenGL renderer and have their OpenGLHint=ON . The antialiasing can be set globally by using the GlgAntiAliasing global configuration resource. This attribute is ignored in the Java version of the Toolkit.
Point List
A list of polygon's control point. Allows you to change the order of points in the polygon as well as add and delete points from the polygon.
Rendering
A slot for attaching an optional
Rendering
object to control an expanded set of rendering attributes, such as gradient fill, cast shadows, fill level and arrow heads. The rendering object is accessible by using the Add/Edit Rendering buttons in the Object Properties dialog. To delete the rendering object, use the Delete Rendering button in the Rendering object properties. The attribute assumes the value of NULL if no
rendering
object is attached. See Rendering on page 78 for details.
When a rendering object is added to all objects in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added rendering objects (the attributes are constrained if the Constrained Clone, the default, setting is used).
Parallelogram
A parallelogram is a four sided polygon that includes implicit constraints to keep the opposite sides parallel. The parallelogram has only three control points and one constrained point. The attributes of a parallelogram are the same as the attributes of a polygon except that, because a parallelogram is always closed, the OpenType attribute is not present.
When a parallelogram is "exploded" in the Builder it becomes a regular four-sided polygon. The constraints that keep its sides parallel are removed, and the fourth point becomes a simple control point.
Note that there is no "Rectangle" object. The GLG Graphics Builder has a "rectangle" button, but this simply creates a parallelogram with right angles between its sides. This is because a parallelogram needs three points to be uniquely defined in three-dimensional space. The Builder allows you to create a rectangle by selecting two points, but this is just a convenience. The third point is automatically selected for you according to the current view.
Arc
The Arc object is used to represent both arcs and circles. One part of an arc is a section of a circle's perimeter. A chord arc simply joins the two ends of the curve with a straight line, while a sector arc is shaped like a piece of a pie, with two straight lines joined at the center of the circle describing the extent of the third, curved side. A circle is simply the special case of an arc whose interior angle is 360°.
An arc has two control points: a center and a vector point. A vector from the center point to the vector point defines a line perpendicular to the arc plane. As you move either of the two ends of this vector, you can see the arc twist in space. The length of this normal vector is not used, only its orientation in space.
Since the arc vector is perpendicular to the arc plane, the vector point of the arc coincides with its arc's center point in the main projection. Also, visually, the vector point is on top of the center point, so selecting the point in the center of the arc and moving it rotates the arc's vector instead of moving the arc's center point. To access the center point, use Shift+click and the point selection arrows in the Control Point dialog, and use the Object Move Point to move the arc.
Like the parallelogram, the arc is simply a special case (sub-class) of the polygon, so it has the usual polygon attributes, like LineType and FillColor . In addition, an arc has the following attributes:
ArcFillType
Defines the type of the arc: GLG_CHORD or GLG_SECTOR.
AngleType
Defines the way the arc's angles are defined. Possible choices are GLG_START_AND_ANGLE and GLG_START_AND_END.
StartAngle
and
EndAngle
Define the angular position of the start and end points of the arc relative to its center. The angles are measured in degrees (counter clockwise). The StartAngle is always measured from the 3 o'clock position. The
EndAngle
is measured relative the
StartAngle
if
AngleType
is set to GLG_START_AND_ANGLE, and relative to the 3'o'clock position if the value of
AngleType
is GLG_START_AND_END. A circle is represented as an arc with a start angle of 0° and an end angle of 360°.
Radius
Defines a radius of an arc's curved edge.
Resolution
The arc's resolution is the number of line segments used to render its perimeter. A circle drawn with a resolution of 5 is simply a regular pentagon. The default value for this is 100. A smaller value may be used for small arcs and circles to increase performance.
As with the parallelogram, an arc may be exploded in the Builder into its constituent polygon. The center and vector control points disappear, and simple polygon control points are shown on the arc's perimeter.
Spline
The spline is a multi-point Bezier or Catmull Rom cubic spline used to render curves in 2D or 3D space. A one-segment spline is a parametrically represented curve controlled by 4 control points. The shape of the segment may be changed by dragging the control points. The multi-point spline is a "blending" of one or more spline segments with a variable number of points. The spline starts and ends at the first and last control points respectively. The intermediate control points control the curvature and shape of the spline.
Like the parallelogram, the spline is a special case of the polygon, so it has the usual polygon attributes, like LineType and FillColor . The spline has two additional attributes:
SplineType
Defines the type of a spline, GLG_B_SPLINE (Bezier) or GLG_C-SPLINE (Catmull Rom). The Catmull Rom spline passes through the control points, while the Bezier spline yields a smoother curve due to its continuous second derivative.
SplineResolution
The spline's resolution is the number of line segments used to render each spline segment. The default value for this is 10. A larger value may be used to increase the rendering quality of splines with large segments or high curvature.
Text
The text object is used to place labels and legends on a GLG drawing. There are four types of text object, which differ both in their behavior and in the number of control points:
FIXED
Has one control point defining its position. The text font size is defined by the
FontSize
attribute, and is not controlled by a bounding rectangle.
SCALED
Text has two control points defining a rectangle in which to fit the text. The
FontSize
attribute defines the maximum and the
MinFontSize
attribute controls the minimum size allowed. The actual size of the font is determined dynamically by constraining the text to the rectangle. Note that the scaling done is not infinitely variable: different sizes of text are selected from the fonts in the font table according to the size of the bounding rectangle. Setting
MinFontSize
to -1 may be used for automatic text label decluttering, in which case the text will disappear if the drawing is zoomed out of and there is not enough space to draw the text inside the rectangle.
SPACED
Text has three control points. The letters of the text are evenly distributed along the line connecting the first two points. For multi-line text, all text lines are parallel to the first line, and the start position of each line is aligned with the line connecting the first and third control points. Similar to the SCALED text, the SPACED text is fit to the parallelogram defined by it's tree control points, with the
FontSize
and
MinFontSize
defining the maximum and minimum font sizes for scaling.
SCROLLED
Text has two control points, same as a SCALED text, but fitting is done only in the vertical direction. It also has a cursor, which allows using the object in a text input widget. It's superseded by the
native text input
objects.
All text objects have the following attributes (in addition to control points):
TextType
Can have the following values:
Fixed
(GLG_FIXED_TEXT)
Scaled
(GLG_AUTOSCALED_TEXT)
Spaced
(GLG_SPACED_TEXT)
Scrolled
(GLG_SCROLLED_TEXT).
Direction
Defines whether text is GLG_HORIZONTAL, GLG_VERTICAL, GLG_VERTICAL_ROTATED_RIGHT or GLG_VERTICAL_ROTATED_LEFT.
Anchor
Defines vertical and horizontal.text alignments relative to the text's control point for the FIXED text, or within the text bounding box for other text types. The choices are CENTER, LEFT, or RIGHT for horizontal alignment, and CENTER, TOP, or BOTTOM for the vertical.
The corresponding defined constants are GLG_HCENTER, GLG_HLEFT, GLG_HRIGHT and GLG_VCENTER, GLG_VTOP, GLG_VBOTTOM. The two choices are combined (logical OR) to define the resource value.
TextColor
Defines the color of the text.
Compatibility Note: The name of this attribute changed in the release 2.9. Previously, the default attribute name for this attribute was EdgeColor. The GlgCompatibilityMode global configuration resource may be set to obtain behavior compatible with the earlier versions.
FontType
Specifies the type of the font used to draw the text.The
FontType
is the row index in the font table attribute for a viewport. (Each viewport can have its own font table.)
FontSize
Defines the font size of the FIXED text, or the maximum font size to use for fitting other text types. The
FontSize
is a column index to the viewport's font table. That is, the
FontType
specifies a row in the font table, and the
FontSize
specifies the column.
MinFontSize
Specifies the minimum font size to use when fitting the text.The
MinFontSize
is a column index to the viewport's font table. Setting
MinFontSize
to -1 activates automatic decluttering feature for SCALED and SPACED text types. In the case the text will not be drawn if there is not enough space to fit the smallest font (0) into the text area.
SizeConstraint
This attribute is used to synchronize the fitting of SCALED and SPACED text objects. If more than one text object is used, fitting may yield different font sizes due to different area sizes or different string lengths of each text object. As a result, they will be rendered using different font sizes.
The actual value of this attribute is irrelevant, because it is determined dynamically. However, if the attribute is constrained, all text objects with constrained
SizeConstraint
attributes will vary together, using the same font size regardless of the string length and other conditions. The
MinFontSize
for all constrained text objects has to be set to the same value as well.
If several text objects have constrained
SizeConstraint
attributes, they all will be displayed using the smallest needed font size in the group. To avoid constraint loops, the font size will stay small until the drawing is resized, even if the original reason for using the small font size has been eliminated.
TextString
This is the text string displayed by the text object. If the text string contains the \n (ASCII NL:) and \r (ASCII CR) characters, they will be used as line separators and the text will be displayed in multiple lines. The
TextString
of a multi-line text can be edited only by using the text edit field of the Attribute Object dialog (ellipsis button 
).
Box Attributes
A slot for attaching an optional
Box Attributes
object to control attributes of an optional box drawn around a text object. A filled box may be used to provide a background for drawing a text object. The box attributes object is accessible by using the Add/Edit Box Attributes buttons in the Object Properties dialog. To delete box attributes, use the Delete Box Attributes button in the Box Attribute properties. The attribute assumes the value of NULL if no
box attributes
object is attached, in which case no box is drawn. See BoxAttributes on page 80 for details.
When a box attributes object is added to all text objects in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added box attribute objects (the attributes are constrained if the Constrained Clone, the default, setting is used).
Rendering
A slot for attaching an optional
Rendering
object to control an expanded set of rendering attributes, such as gradient fill, cast shadows, fill level and arrowheads. The rendering object is accessible by using the Add/Edit Rendering buttons in the Object Properties dialog. To delete the rendering object, use the Delete Rendering button in the Rendering Object properties. The attribute assumes the value of NULL if no
rendering
object is attached. See Rendering on page 78 for details.
When a rendering object is added to all objects in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added rendering objects (the attributes are constrained if the Constrained Clone, the default, setting is used).
Note that a text object's behavior under various graphical transformations is limited by the availability of suitable fonts. For reasons of efficiency, GLG text objects contain text displayed in un-transformed fonts, taken from the viewport's font table. This limits a text object's ability to react appropriately to shear and scale transformations, for example, but greatly improves real-time update performance by eliminating multiple instances of similar fonts scaled slightly differently.
Marker
The marker object is used to mark a position in space. For example, a point graph might be presented as a collection of marker objects arranged on a graph. It has a fixed size, and does not change when a window is resized.
Markers have only one control point defining their position. A marker object also has the following attributes:
MarkerType
Defines the shape of the marker. When drawn, a marker consists of components like cross, rectangle, filled rectangle, circle, filled circle and dot. Any mix of components can be chosen to represent a marker as defined by the marker type. The components are chosen from the following list:
The marker drawn is a superposition (Logical OR) of the set chosen by the MarkerType value.
MarkerSize
Defines the size of the marker in pixels.
FillColor
and
EdgeColor
Define colors used to draw marker's components.
Rendering
A slot for attaching an optional
Rendering
object to control an expanded set of rendering attributes, such as gradient fill, cast shadows, fill level and arrow heads. The rendering object is accessible by using the Add/Edit Rendering buttons in the Object Properties dialog. To delete the rendering object, use the Delete Rendering button in the Rendering object properties. The attribute assumes the value of NULL if no
rendering
object is attached. See Rendering on page 78 for details.
When a rendering object is added to all objects in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added rendering objects (the attributes are constrained if the Constrained Clone, the default, setting is used).
Image
The image object is used to represent graphical images in GIF, JPEG and BMP formats. The GIF and JPEG formats are supported across all platforms, while the BMP format is supported only in the C/C++ version on Windows. TIFF images are also supported in the Java version of the Toolkit. Transparent colors in GIF images are supported in the OpenGL renderer mode and in the Java version of the Toolkit. The image transparency is also supported via the Visibility attribute.
An image may be of fixed size, defined by the size of the image in the original file, and have one control point. The image object may also be resizable, in which case it's size is adjusted to fit the rectangle defined by the image's two control points.
An image object has the following attributes:
ImageType
Defines the type of the image: a fixed-size (GLG_FIXED_IMAGE) with 1 control point or a scalable (GLG_SCALED_IMAGE) with two control points.
ImageFile
Defines the location of the image file in the GIF or BMP format. The type of the file is determined by the file's extension:
If the ImageFile attribute defines a relative file name, the Toolkit tries to find the file it in the following order:
- attempting to load the file relative to the current directory
- attempting to load the file relative to the directory of the drawing
- trying to locate the file in one of the directories defined by the GLG_PATH environment variable or the GlgSearchPath configuration parameter.
A List transformation may be attached to the ImageFile attribute to specify a list of image files for implementing image dynamics.
Anchor
Defines the vertical and horizontal alignments of the fixed size image relative to its control point. The choices are CENTER, LEFT, or RIGHT for horizontal alignment, and CENTER, TOP, or BOTTOM for the vertical.
The corresponding defined constants are GLG_HCENTER, GLG_HLEFT, GLG_HRIGHT and GLG_VCENTER, GLG_VTOP, GLG_VBOTTOM. The two choices are combined (logical OR) to define the resource value. The attribute has no effect for scalable images.
GIS Object
Generic Logic provides a GIS Map Server product designed for real-time rendering of high-resolution maps with millions of objects. There are a variety of applications that might need to display a map in the background as contextual information, and place GLG objects on top of the map to represent dynamic or static icons. Such applications need to provide map zooming and panning functionality, handle window resizing and user interaction with the icons.
The GIS object seamlessly integrates Map Server functionality into the GLG drawing, both in the application and the Graphics Builder. The GIS object displays a map image in a selected GIS projection and transparently handles all aspects of interaction with the Map Server, automatically issuing map requests every time the map is resized, panned or zoomed. The GIS object supports integrated zooming and panning, as well as utilities for converting from screen or world coordinates to latitude/longitude in the selected projection and vise versa. Refer to Viewport on page 56 for details of the integrated GIS Zooming.
The two control points of the GIS object define the size of the map image. When the GIS object is used to provide a background map for the drawing, its points' values may be set to (-1000, -1000, 0) and (1000, 1000, 0) to cover the whole drawing (in the Builder, Shift -click on the control point with the mouse to enter exact coordinates).
The following attributes of the GIS object provide easy resource-based access to the underlying Map Server functionality (refer to the GLG Map Server Reference Manual for more information):
FillColor
Defines the color of the map's background, which is visible when the map is sufficiently zoomed out.
GISDisabled
Disables the GIS object for quick editing.
GISProjection
Defines the projection used to render the map: GLG_RECTANGULAR_PROJECTION or GLG_ORTHOGRAPHIC_PROJECTION. The rectangular projection displays the world as a rectangular region and is convenient for displaying detailed maps, where parallels and meridians appear as straight lines. The orthographic projection maps the whole world onto a sphere, and is often used for the top-level globe-like views.
GISCenter
Defines the latitude and longitude of the map to be displayed in the center of the GIS object. This attribute is of the geometrical (G) type and is a set of three values. The first two values supply the longitude and latitude correspondingly, while the third value must be set to zero. The attribute is automatically adjusted when integrated GIS panning is performed.
GISExtent
Defines the extent of the map visible in the GIS object. This attribute is of the geometrical (G) type and is a set of three values. The first two values supply the X and Y extents, while the third value must be set to zero. For the rectangular projection the extents are measured in degrees of the longitude and latitude. For the orthographic projection the extents are specified in meters as dictated by the Open GIS Standard. The default extent value for the orthographic projection is 14,000,000, which is slightly bigger then the earth's diameter. The attribute is automatically adjusted when integrated GIS zooming is performed.
GISAngle
Defines the map rotation angle in degrees. For example, an application can set the rotation angle to display a map from the point of view of an airplane pilot. The map rotation feature is supported only in the rectangular projection; the attribute's value is ignored in the orthographic projection. The attribute is automatically adjusted when integrated GIS rotation is performed.
GISStretch
Defines the stretch mode. If the attribute is set to YES, the map is stretched, otherwise the aspect ratio of the map is preserved and the map image may include an area which is slightly bigger then the area defined by the GISExtent attribute.
GISDataFile
Specifies a Server Data File (.sdf) which describes the dataset to be used by the Map Server to generate the map image. It may be specified using either a relative or absolute path. This attribute is used only by the C/C++ and ActiveX version of the Toolkit, as well as the Graphics Builder, which use the Map Server in the form of a C library.
GISMapServerURL
Specifies the Map Server URL to be used by the Java version of the Toolkit. The URL has to have a web server based GLG Map Server setup as described in the GLG Map Server Reference Manual. This attribute only affects the Java version of the Toolkit, which connects to a web-based GLG Map Server to retrieve the map image. The GIS Object handles all aspects of connecting to the Map Server URL with proper parameters.
GISLayers
Defines a list of layers to be displayed in the generated image. The value of this attribute is a comma separated list of layer names, defined in the Server Data File (.sdf). The "default" string may be used to enable the layers whose "DEFAULT ON" attribute is set to YES in the Layer's Information File (.lif). See the GLG Map Server Reference Manual for details.
GISVerbosity
May be set to a value from 0 (no debugging output) to 5 (maximum debugging output) to debug problems in the Map Server setup. This attribute has no effect in the Java version of the Toolkit.
GISDiscardData
Controls Map Server data caching. If set to NO (default), the Map Server data is cached resulting in faster image generation. For map images that are generated only once or very infrequently, the attribute may be set to YES to discard data after generating the image, saving memory. This attribute has no effect in the Java version of the Toolkit.
Refer to the GLG Map Server Reference Manual for more information on the GLG Map Server, its setup and usage.
Viewport
A viewport object is a GLG encapsulation of a window, and is rendered as a non-transparent rectangular region into which graphical objects can be placed. You can think of it as the drawing surface for a GLG drawing. Unlike a simple rectangle, however, the viewport object contains the objects that appear in front of it (which can include other viewports). This creates a convenient way to group objects in a GLG drawing. A viewport can control the resizing of its member objects, as well as the magnification, angle, and lighting with which a drawing is seen.
A viewport also differs from a simple rectangle in that it always appears in the plane parallel to the screen. You cannot view a viewport from an oblique angle.
The viewport has its own coordinate system with the origin at the center of the viewport and the Z axis perpendicular to the plane of the viewport's rectangle. The corners of the viewport are [-1000,-1000] and [1000,1000] in the viewport's coordinate system, and this mapping is maintained when the viewport is resized. The viewport's coordinate system is used to interpret the coordinates of any objects drawn in the viewport. When the viewport is resized, all objects within are resized as well.
Panning and zooming affects the mapping of the viewport's coordinate system. For example, if the viewport is zoomed in to by a factor of 2, the corners of the viewport will correspond to (-500 -500) and (500 500) instead of (-1000 -1000) and (1000 1000) without zooming.
To add objects to the viewport, the editing focus has to be moved in the viewport, by either going "down" into the viewport using the
Hierarchy Down
button 
, or by setting the editing focus by Ctrl-Shift-clicking on the viewport. When finished, use the use the
Hierarchy Up
button 
or the Main Focus button 
, depending on the action used to set the focus inside the viewport.
Note: If the focus was moved into the viewport, the Hierarchy Down button will be disabled. To traverse down into the viewport's objects, use the Hierarchy Down button to get inside the viewport, and then use it again to get inside the viewport's objects.
A widget is defined to be a viewport that has resources ( HasResources is YES) and is named $Widget . When the GLG API reads a drawing from a file, it looks for a widget definition to use. The widget name should appear only once in a drawing. All subsequent resource read and set operations implicitly refer to this object. In an application, a viewport could be used to define a graph or a control.
A viewport's attributes may be divided into four categories. The first group of attributes controls the appearance of the viewport's background rectangle, and the second controls the display of its child objects. A third group of attributes controls some aspects of event handling and viewport interactive behavior. The last group is made up of window-specific attributes, and is embodied by the screen object, described in the next section.
In addition to the two control points, the viewport backing rectangle has the following attributes:
EdgeColor
Defines a border color for the viewport rectangle.
LineWidth
Defines the viewport rectangle's border width.
FillColor
Defines a background color of the viewport.
DepthSort
The
DepthSort
attribute defines how to render overlapping objects inside the viewport by controlling hidden surface removal. A hidden surface is one whose view is fully or partially blocked by another object. For example, a drawing might consist of two circles. If you look at the circles from an angle where the position of one circle is between the viewer and the other circle, the blocked circle will not appear to be drawn if the objects are depth-sorted.
The algorithm used to sort objects is known not to work in some complicated cases, but provides much faster real time graphics than other techniques and works well for all the GLG Graph Widgets. However, since any depth-sorting algorithm slows down the update procedure for a drawing, use it only when necessary.
This attribute may be set to NO, YES, INHERIT, PARTS, or SPECIAL. Only NO, YES and SPECIAL can be applied to viewports and are used to turn depth sorting off and on. SPECIAL uses a faster but less precise depth sorting algorithm, described in more detail in Group. The other options have no meaning for viewports, but are used for other objects that use this attribute, such as groups. A viewport cannot inherit the DepthSort attribute.
Pan
The
Pan
attribute controls integrated scrolling. If it is set to YES, the viewport displays scrollbars and handles scrolling when the drawing extends beyond the viewport's visible area.
ZoomEnabled
The
ZoomEnabled
attribute controls integrated zooming and panning. If it is set to YES, the viewport handles the following accelerator keys:
Shift-click-drag - ZoomTo (see details below)
t - start ZoomTo mode (click and drag the mouse to finish)
T - start custom ZoomTo mode (see details below)
f - fit the drawing to the visible area of the viewport
F - fit the area of the drawing defined by an object named GlgFitArea to the visible area of the viewport
n - reset zoom. In the GIS zoom mode with map in the ORTHOGRAPHIC projection, resets zooming, but keeps the GIS center unchanged. In the RECTANGULAR projection, resets zooming and paning, but keeps the rotation angle unchanged.
U - anchor on the upper edge of the drawing
D - anchor on the lower edge of the drawing
R - anchor on the right edge of the drawing
L - anchor on the lower edge of the drawing
A - rotate the drawing clockwise around X axis
a - rotate the drawing counterclockwise around X axis
B - rotate the drawing clockwise around Y axis
b - rotate the drawing counterclockwise around Y axis
C - rotate the drawing clockwise around Z axis
c - rotate the drawing counterclockwise around Z axis
g - If the mouse is located on top of a GIS object, sets the viewport's GIS Zoom Mode and remembers the selected GIS object. In the GIS zoom mode, the map displayed in the GIS object is zoomed and panned instead of the viewport's drawing. Zooming, panning, ZoomTo and reset accelerators are supported in the GIS zoom mode.
p - in the GIS Zoom Mode, displays the lat/lon and X/Y coordinates of the point at the current cursor position. If the GLG_GIS_ELEVATION_LAYER environment variable is set to a valid elevation layer name, the point's elevation is also displayed.
In the Builder, the zoom and pan accelerators are active only in the Run mode. If ZoomEnabled is set to NO, the accelerators are disabled at run time, but the integrated zooming and panning may still be accessed programmatically.
There are two accelerators for the ZoomTo operation: t and T. The operation can be performed by pressing the `t' key, then using the left mouse button to click and drag the mouse to define the area to zoom to. The user can also zoom to an area by holding the Shift key and then using the left mouse button to click and drag the mouse to define a zooming rectangle. Custom zoom mode is started with `T' and displays the zooming rectangle without performing the zoom operation. It is used for applications that want to provide a custom zooming logic. Performing zoom and pan actions on a viewport generates Zoom and Pan messages. Refer to Appendix B: Message Object Resources of the GLG Programming Reference Manual for details.
ZoomFactor
A read-only attribute of the viewport showing the current zoom factor; may be used to implement custom decluttering (turning layers on or off depending on the zoom factor) or icons of constant size. This attribute is not displayed in the viewport's Property dialog, but is accessible as a resource.
XYRatio
A read-only attribute of the viewport showing the current X/Y ratio of the viewport's window. It may be used to implement icons of constant X/Y ratio for a viewport with Stretch enabled, so that the icons will keep their X/Y ratio constant while other objects in the drawing will stretch. This attribute is not displayed in the viewport's Property dialog, but is accessible as a resource.
ProcessMouse
Controls processing of the mouse move and mouse click events by the viewport and may have the following values:
None
Disables event processing for the viewport. May be used to reduce consumption of the CPU's resources for the viewports that do not need to process any events.
Click
Enables processing of object selection, custom events and highlighting on the mouse click events in the viewport.
Move and Click
Enables processing of object selection, custom events, highlighting and the tooltips on mouse over events.
Move & Click (Named)
Same as Move and Click, but causes object names to be used as the tooltips instead of the objects' TooltipString properties.
The value of the viewport's ProcessMouse attribute is inherited by any child viewports which have ProcessMouse set to None. For example, setting ProcessMouse to process mouse click events for the viewport will enable mouse click processing for all its children.
Refer to Integrated Features of the GLG Drawing on page 97 for details on custom events, highlighting and object tooltips.
Handler
A viewport may become an input widget (or control) by naming an input handler with this attribute. The
Handler
attribute identifies the style of control that is adopted, such as slider, knob, switch, and so on. The use of input handlers is described in Input Objects.
HandlerDisabled
Controls whether or not a viewport input handler reacts to input events. This attribute may be set to NO or YES.
ServerName
Specifies the name of the viewport's built-in communication server. This name is used by client processes to communicate with the viewport's data server. For more information about using external processes to send data to a viewport, see Communicating from a Client Process in Animating a GLG Drawing Using the Standard API.
ServerEnabled
Defines the state of the communication server. This attribute may be set to NO or YES. If it is set to YES, the data server reacts to the messages sent by other clients and performs requested actions.
Add/Edit Light
The Light object keeps attributes that control the viewport's lighting and 3D shading. The Add/Edit Light button may be used to add a light object to the viewport or edit its attributes if it already exists. To delete the Light object, use the Delete Light button in the Light Object properties. See Light Object on page 85 for details.
When a Light object is added to all viewports in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added Light objects (the attributes are constrained if the Constrained Clone, the default, setting is used).
Zooming and Viewing Transformations
Each viewport automatically creates a
Matrix
transformation, which is used for zooming when the viewport is edited in the Builder as well as for integrated zooming and panning at run-time.
User-defined viewing transformations (e.g.
Scale
,
Move, Rotate, Shear)
may also be added directly to the viewport to implement user-controlled zooming, panning or 3D rotating functionalities, which otherwise would require creating a group to contain all objects in the viewport and attaching the transformations to the group. Attaching the viewing transformations directly to the viewport makes it more convenient by eliminating an extra group.
To add a viewing transformation, move the focus inside the viewport, make sure no objects are selected, display the viewport's properties and press the
Add Dynamics
button to add a viewing transformation. Notice that selecting the viewport and adding dynamics adds a transformation to the viewport, transforming its control points, while adding dynamics with the focus inside the viewport adds a viewing transformation which affects the way the objects in the viewport are drawn.
After adding a viewing transformation, the default zooming transformation of the viewport can also be accessed in the Builder. This matrix transformation must always be present, and the Builder prevents it from being deleted or reordered.You can give this transformation a name to access it from a program as a named resource.
A viewport has a secondary screen object which is always attached to the viewport and controls its window-specific display attributes. Use the More button to display screen's properties.
Screen
The screen object is a mandatory child object of a viewport. It is designed to contain window specific attributes of a viewport, and is created automatically every time a viewport is created. It has the following attributes:
Double Buffering
Controls the usage of the double buffering for a screen. This may be set to NO or YES. When set to YES, screen updates are done incrementally off-screen, and all changed portions of the entire screen are updated at once. This usually creates a smoother illusion of motion than updating objects directly on the screen. Double-buffering is turned on by default. It can be useful to turn it off to see updates as they go in complicated drawings, such as a surface graph. If you have a lot of viewports, double buffering may turn to be an expensive resource, as it causes the window manager to allocate memory for the off-screen pixmaps. Turn it off if you want to decrease the amount of memory consumed.
Warning : Double buffering is known to cause problems when zooming with high zoom factors in a viewport that has other viewports in it. Zooming in the parent viewport increases the size of the child viewport. If the child viewport has double buffering set to YES, the excessive increase of the size causes the graphics server to exhaust memory trying to allocate a huge off-screen pixmap. The GLG Toolkit driver tries to catch this condition and disables double buffering, producing an error message if the viewport size becomes too big. But it may be too late in some cases. Turn double buffering off for the children viewports if planning to zoom into the parent viewport with big zoom factors.
Resizable
Controls whether or not objects in the viewport are resized when the size of the viewport's window is changed. If set to YES, a default GLG coordinate system is used to define objects. This coordinate system maps the extent of the viewport to the [+1000;-1000] coordinate range, and all objects in the viewport are resized when the viewport's size is changed. Use the NoResize resource name for programmatic resource-based access of this attribute.
If set to NO, the screen coordinate system is used to define objects. In this coordinate system, coordinates are defined in screen pixels and objects' dimensions are not changed when the viewport is resized. The origin of the screen coordinate system is located in the top left corner of the viewport, with the X axis pointing right and the Y axis pointing up. The direction of the Y axis is opposite to the default Y axis direction in 2D windowing systems to preserve the X, Y and Z axis relations in 3D space.
Stretch
Controls mapping from view coordinates to window coordinates. If it is set to RESIZE, the original ratio of the viewport's height to width is not preserved and things may look distorted when the viewport is resized. If turned off (set to NO), the ratio is preserved. In this case
PushIn
attribute controls the rest of the mapping.The RESIZE AND ZOOM setting allows to stretch the viewport on both resizing and zooming. For more details about the mapping from view coordinates to window coordinates, see Coordinate Systems in Structure of a GLG Drawing.
PushIn
Controls which parts of the viewport are visible when Stretch is turned off. If
PushIn
is set to YES, the screen scaling factor is chosen in such a way that the viewport frame (a rectangle defined by two points with coordinates
(-1000,-1000)
and
(1000,1000)
) is completely visible in the window. Some other parts of the drawing may be visible as well depending on the screen ratio. If PushIn is set to NO, the screen scale factor is chosen as an average of the horizontal and vertical scaling factors defined by mapping the viewport frame to the window's border. Depending on the screen ratio, some parts of the viewport frame may be clipped off.
OpenGLHint
If set to
ON
, the screen's viewport will use an OpenGL renderer if it is available. Otherwise, a native windowing renderer will be used. This flag is ignored in the Java version of the Toolkit, where the Java2D OpenGL renderer is always used.
Even if the
OpenGLHint
is set to
ON
, the OpenGL renderer may be disabled by the
-glg-disable-opengl
command-line option, setting the
GLG_OPENGL_MODE
environment variable to
False
, or setting the
GlgOpenGLMode
global configuration resource to 0. Refer to OpenGL or Native Windowing System Renderer on page 16 for details.
OpenGL
Read-only attribute for the programming use that provides the current status of the OpenGL renderer. It is set to
ON
if the OpenGL renderer is successfully initialized and is used for rendering objects in the screen's viewport.
ShellType
If this attribute is set to GLG_DIALOG_SHELL or GLG_APPLICATION_SHELL, the viewport appears in its own window, at the same level in the window hierarchy as the program operating it. The difference between the two is that the GLG_DIALOG_SHELL value always appears on top of other windows. The attribute may also be set to NONE (GLG_NO_TOP_SHELL), in which case, the viewport is simply a child window of a larger drawing.
WidgetType
The widget type may be selected from the list of possible widget types. For more information about widget types, see Native Widgets on page 123.
ShadowWidth
Defines the width of shadows. If the value differs from 0, the shadow bevels are drawn around the borders of the viewport. The sign of the ShadowWidth controls the type of the bevels: raised shadows for positive values and depressed shadows for negative values.
Compatibility Note: The ShadowType attribute present in pre-2.5 releases has become obsolete, and the type of the bevels is controlled by the sign of the ShadowWidth. Also, starting with the 2.5 release, the bevels will be drawn even for the drawing area widget. In the previous releases, the bevels were drawn only for widget types other than the drawing area.
ExactColor
When using widget types besides Drawing Area on X Windows, this boolean attribute instructs the native widget to use the exact value specified by the
FillColor
attribute rather than take the closest available entry from the color table.
GridValue
Defines the grid spacing, in "world" coordinates. A viewport's corners are mapped to (-1000; -1000) and (1000; 1000) in this coordinate system. If it is zero, the grid is not drawn.
SpanX, SpanY
Define the mapping of the world coordinate system to the visible area of the viewport. The default value of the SpanX and SpanY attributes is 1000, which causes the corners of the visible area of the viewport to correspond to the coordinates (-1000, -1000) and (1000, 1000) in the absence of zooming and panning and with Stretch set to YES. The SpanX and SpanY attributes may used to change the mapping.
Add/Edit Color Table
The color table defines the colors available for use in a viewport. If not defined, the color table is inherited from the parent viewport, or the default GLG color table is used if there is no parent. On TrueColor systems with more than 256 colors (and in Java) the color table is not used for rendering: it is used only to define the number of colors in the Graphics Builder's color palette.
The Add/Edit Color Table button may be used to add a custom color table to the viewport or edit color table parameters if it already exists. To delete the color table, use the Delete Table button in the color table properties. See Colortable on page 81 for details.
When a color table is added to all viewports in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added color tables (the attributes are constrained if the Constrained Clone, the default, setting is used).
Add/Edit Font Table
The font table that lists the fonts available for use in the viewport. If not defined, the font table is inherited from the parent viewport, or the default GLG font table is used if no parent exists.
The Add/Edit Font Table button may be used to add a custom font table to the viewport or edit fonts in the font table if it already exists. To delete the font table, use the Delete Table button in the font table properties. See Font Table on page 83 for details.
When a font table is added to all viewports in a group using the group's Edit All option, the Attribute Clone Type option of the Builder controls the constraining of the corresponding attributes of the added font tables (the attributes are constrained if the Constrained Clone, the default, setting is used).
Screen Transformation
The screen transformation is used by the screen object to adjust the drawing when the screen size changes. The parameters of the transformation are automatically set by the screen object, but they may be used for constraining purposes to obtain offsets in screen pixels. For example, the top part of the resource browser in the Builder has constraints that make it non-resizable, keeping a constant pixel size when the resource browser window is resized.
To obtain such an effect, a
MoveX
or
MoveY
transformation may be used, with the
Divide
transformation attached to its
Factor
attribute. The divisor of the
Divide
transformation is then constrained to the corresponding
X
or
Y Scale
of the screen transformation. This annuls the result of the screen size changes, making the move transformation maintain its offset in pixels rather then the world coordinates.
To get access to the parameters of the
Screen Transformation
, edit the attributes of the viewport object and press the
More
button to access the screen's attributes, then press
Edit Dynamics
to edit the screen's transformation.