Together with map properties described in chapter 11 “Properties of maps and their components”, in ObjectLand the properties of cataloged themes as well as of the browsed ones are defined. A set of theme characteristics forming its properties is absolutely different than the map properties. Such theme components as layers and feature types also have their properties.
To get the properties of the browsed theme, it is necessary to perform the menu command of the browser window Edit+Properties or push the toolbar button 
. To browse the properties of the cataloged theme without browsing the theme itself it is possible to select the corresponding theme in on of the panes of the navigation window and perform the menu command Edit+Properties or push the button . In both cases a property sheet “Properties of theme” shown at figure 15-1 will be opened.
Figure 15-1. Property sheet “Properties of theme”, page “Fragment”
The page “Fragment” serves for viewing and editing numeric parameters of displayed theme area. All coordinates and sizes are indicated in map units.
Since there are dependencies between displayed parameters (for example, the center of the area is always equal to the half-sum of the opposite corners), when some parameters are changed, others are recalculated automatically.
If the property sheet “Theme properties” is opened for the browsed theme, changes of properties may not result in changes of the size of browser window, that is why the system interprets the specified sizes values as user's wishes which are performed until it doesn't change the window size.
Page “Parameters” (figure 15-2) serves for browsing and changing parameters related to the buttons of the mode toolbar of map browser window. These parameters include Scrolling step, Rotation angle step and Zoom step. On this very page the parameter Extent of intersection with feature to be selected is specified. It controls the work of selection modes by rectangle, circle and polygon, and also selection modes by buffer zone. Selection threshold is indicated in percentage from the length of line features and the area of area features. When the value is minimal (0 per cent) all the features which at least touch selection region are selected, when it is maximal (100 per cent) – only those which are entirely included into the region are selected. The value for this parameter can be specified from the keyboard in the form of a number, but it is possible just to move the slider to the necessary position.
Figure 15-2. Property sheet “Properties of theme”, page “Parameters”
The parameter Buffer zone width specifies a value in map units for the width parameter used in selection modes by buffer zone of a polyline or a feature.
If the box Zoom together with window is checked, changing browser window size will result in changing scale (that is, the image is zoomed together with the window), when it is cleared the scale isn't changed.
The box Filter controls theme filter actions. When it is cleared the presence of filter is not taken into account during theme display.
The page “Grid” (figure 15-3) enables the user to control parameters of coordinate grid display in the map browser window.
Figure 15-3. Property sheet “Properties of theme”, page “Grid”
Coordinate grid is a set of lines parallel to coordinate axes of the map. One pair of lines goes through the specified base point; other grid lines are drawn with the specified indent step along horizontal and vertical axes. It is possible to select any color for displaying the grid line. The box Visible allows turning on and off the grid display without changing other grid parameters.
Page “Background” (figure 15-4) serves for setting background displaying style. Any fill style from the shared or current library can be chosen as a background.
Figure 15-4. Property sheet “Properties of theme”, page “Background”
If the radio button Default is checked the standard color of window background set in Windows system (usually white) is used as a background. This color can be changed by Windows tools.
The page “Selection styles” (figure 15-5) serves for setting the displaying style for selected features. The page is made of four subpages which enable the user to specify styles for displaying line features, boundaries of area features, filling and/or hatch of inner regions of area features accordingly. Any styles from shared or current library can be taken, however, their color is set separately, not from the library. For all the elements of selection style one and the same color is used.
Figure 15-5. Property sheet “Properties of theme”, page “Selection styles”
When choosing a selection style for filling the system automatically transforms a color image into a monochrome one with the color of the foreground specified by the user and transparent background color. The lighter the selected filling color is, the bigger percentage of pixels will be transparent in its monochrome variant. As a result, the filling of selected area feature is usually semitransparent. Through transparent parts of selection filling it is possible to see initial filling of the present feature and other features (for example, texts) located above the selected one. Only when the black solid fill style is set for displaying selected area features, these features will not be transparent at all since such a filling doesn't produce any transparent pixels. The matter doesn't concern the black selection color (any color can be used), but the black library fill style.
When a point feature is selected, its bounding box is displayed as selected area feature. However, the feature symbol is always visible, even when selection filling is not transparent.
If the radio button Default is checked, a standard set of styles is used for selection: for line features – a thick red line, for area and point features – a thin red boundary and a red semitransparent filling, hatch is not used.
The page “Scale zones” (figure 15-6) enables specifying display scale ranges (scale zones) which can affect display of features of different layers and types.
Figure 15-6. Property sheet “Properties of theme”, page “Scale zones”
Initially, a list of scale zones is empty. When the button Add is pushed, the system opens a dialog box “Adding scale zone”, in which the user should enter a real number which becomes the limit of the scale zone. Adding a limit for the first time results in creation of two scale zones, one of which corresponds to the scale range from 0 to the added limit, and the second one – to the scale range from the limit to the infinity. Infinite upper scale limit is denoted by a dash in the corresponding list column.
It should be kept in mind that displaying scale is measured by the number of map units in one logical centimeter of the screen. The current scale value is shown in the status bar of map browser window.
If the button Add is pushed repeatedly, adding the second and further limiting scale values is performed, and each time a new scale zone is added. All displaying styles of layers and feature types, specified for zone being divided will be effective for the new zone as well. The list of specified scale zones in the order of increasing limits is displayed on page “Scale zones”.
To change one of the limit values it is necessary to select the zone from the list for which the value being changed is the lower limit and push the button Change. In the opened dialog box “Changing scale zone” it is possible to specify a new value for the lower limit of the zone. The new value should be smaller than the upper limit of the same zone and greater than the lower limit of the previous zone in the list.
For removing one of the scale zones the button Remove is used. The zone which is being removed merges with the previous zone in the list, that is why the button Remove doesn't work for the first zone.
The checkbox Use scale zones duplicates the toolbar button 
of map browser window. If this box is cleared, scale zones are not taken into account in map display. The list of assigned scale zones is kept, but it is not used until the mode of using them is turned on.
In navigation windows the names of themes containing scale zones are marked by a sign with a red-white scale ruler: 
.
The page “Transformation” (figure 15-7) allows setting coordinate transformation of features which is performed when displaying the given theme.
Figure 15-7. Property sheet “Properties of theme”, page “Transformation”
The checkbox Transform coordinates is checked by default, however the transformation itself is not set, therefore all the features are displayed with those coordinates which they have in the corresponding map. Further, after the transformation is set, this checkbox permits switching execution of the transformation.
The pane Settings serves to set parameters of the required coordinate transformation.
Pushing the button Set up starts the coordinate transformer setting wizard which will be described in detail in the chapter 20 “Transformation of coordinates”.
The button Reset cancels the transformation setting made previously.
The button Copy is used in the case when the same coordinate transformation is to be used for several themes or theme layers. Pushing this button opens the dialog box “Select source” shown at figure 15-8.
Figure 15-8. Dialog box “Select source”
In the pane of the box all themes and theme layers for which a coordinate transformation is set. Bold lines indicate layers and also those themes for which their own coordinate transformation is set. The user can select one of layers or one of bolded themes, and after pushing the OK button the corresponding coordinate transformation will be copied into the current theme.
The coordinate transformation set for the theme in whole will be performed only for those theme layers for which their own transformation is not set.
The page “Permissions” serves for displaying permissions of the current user to the theme. These permissions will be described in chapter 87 “Permissions to GDB and its components”
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