Styles can be set and locally derived in MDL controls. They affect the current control and also recursively all its children.

For example, to specify the style for a single Window control the style tag can be used like this:

Window { 
  style = ExistingStyleName 
  ... 
} 

To locally derive from an existing style, one can write:

Window { 
  style NewLocalStyle {
    derive = Application.default // inherit the default Application style
    colors {
      bg = blue   // background color
      fg = yellow // foreground color
    }
  } 
  ... 
} 

The derive tag can be omitted to inherit from the style that is currently active, regardless of which that is (see also the style stack, which is mentioned below in “How MeVisLab Applies the Styles”). It is also possible to omit the style prefix, in which case MeVisLab uses the detected one.

A local style can also be anonymous:

Window { 
  style { 
    colors { bg = blue button = red } 
  }  
  Box {
    layout = Grid
...

Figure 11.12. Redesigned Panel

	Tip
	MATE offers auto completion for style attributes. See the figure below.

Figure 11.13. Entering Style Settings

How MeVisLab Applies the Styles

Before a window is created, MeVisLab initializes a stack with the default style. The name of it is “<style prefix>.default”, e.g., Application.default (see below how MeVisLab determines the style prefix). Then it recursively creates all MDL controls, beginning with the Window control.

For each control, MeVisLab checks if either a style is specified or if a style is derived locally (local styles are explained below). If one of both is true, then it pushes this style onto the stack and applies it to the widgets that are created by the control. This style is also applied to all sub controls, unless they push another style themselves. After the control is created, the style is popped again.

MeVisLab looks up styles as follows:

How MeVisLab Determines the Style Prefix

In Application mode, the style prefix is the name of the application macro module. The fallback style prefix is either the value of the MDL preferences variable ApplicationStyle, or “Application” if ApplicationStyle is not specified.

In Panel mode the style prefix is either the value of the MDL preferences variable PanelStyle, if it is given, or “Panel”. The fallback style prefix is always “Panel”.

Figure 11.14. ExampleToggleButton with Application Style Panel

To style a window like above for testing, use the style tag as follows:

Window { 
  style = Application.default
  
  Category {
    Box {
    ...
    }
  }
}

How to Define MDL Styles

A style is defined globally using the DefineStyle tag. The style name may include a prefix separated by a dot from the actual name, but it is not required (see “How MeVisLab Applies the Styles” above on how MeVisLab looks up styles by name). There are two possibilities to position the definition of a named style:

DefineStyle AnyStyleName { 
   derive = _default 
   colors {
     bg = black
     fg = black
     button = black
   }
} 

DefineStyle BaseStyle { 
  derive = _default 
  ...
} 

DefineStyle Macro1.default { 
  derive = BaseStyle 
} 

DefineStyle Macro2.default { 
  derive = BaseStyle 
} 
...

Custom MDL controls can be created.

The following steps would be necessary to create a MDL control:

Examples for this are in the MeVisLab/Examples package. It includes the controls

Their definitions exist in Examples/Modules/Controls/, their implementations in Examples/Sources/Controls/ (C++) and Examples/Modules/Scripts/python/ (Python). The modules ColorChooserExampleControlTest, DiagramExampleControlTest, and PythonExampleControlsTest demonstrate using the controls.

For example, the ColorChooserExample files are:

The PythonControlExample files are:

Figure 11.15. Color Chooser Example Control