The evaluator can be used to generate entire command lines. There are two types of command lines it can generate.
When the function is run, the return value from the evaluation expression will be executed as if it had always been part of the function.
To use this, simply begin the line with a = character, followed by the expression.
If the expression doesn't return a string to run as a command, the line is simply skipped over and execution moves on to the next line in the function. This lets you have functions that are composed of multiple evaluator command lines with a final command returned at the end.
In this mode, it can generate commands that are used to generate dynamic lists of buttons. For example, Go DRIVEBUTTONS is a dynamic button that generates a list of drive buttons.
This mode is accessed using the @ctx: modifier. The command returned by the expression will be used to generate dynamic buttons.
A number of variables are available to the evaluator in this context. Note that some are only applicable to toolbars in the standalone image viewer, and some only apply to Lister toolbars.
| Variable | Type | Description |
|---|---|---|
dest |
path |
The current destination path. |
dest_shell |
bool |
True if the destination is a shell (virtual) folder hosted by Explorer, otherwise false. |
expanded |
uint |
Returns the number of expanded directories. |
fullscreen |
bool |
Viewer only. True if the viewer is fullscreen, otherwise false. |
key_repeat |
bool |
True if the function was launched from a repeated key press (i.e. the key was held down). |
lister_title |
string |
Returns the current title string of the Lister. |
preparse_dummy |
bool |
True if the evaluator is being called with a dummy filename as part of pre-parsing. Opus will do this for evaluator expressions inside a @perfile block. You should generally respond normally (Opus is querying to find out which values the evaluator expression requires), but you may want to filter out some behaviour (e.g. logging) for pre-parsing. |
selbytes |
uint64 |
Returns the number of selected bytes (files + directories that have had their sizes calculated). |
seldirs |
uint |
Returns the number of selected directories. |
selfiles |
uint |
Returns the number of selected files. |
selimage |
bool |
Viewer only. True if an area of the image has been selected, false otherwise. |
selitems |
uint |
Returns the total number of selected items. |
selpath |
string |
Provides the full pathname of the currently selected file. In a Lister this means the selected file with input focus (e.g. the file you right-click on). In the viewer this means the currently viewed image. Note that main toolbars in the Lister are not necessarily refreshed when the file selection changes, and so a button on the main toolbar using this may not always show the correct information. |
source |
path |
The current source path. |
source_shell |
bool |
True if the source is a shell (virtual) folder hosted by Explorer, otherwise false. |
totalbytes |
uint64 |
Returns the total number of bytes (files + directories that have had their sizes calculated). |
totaldirs |
uint |
Returns the total number of directories. |
totalfiles |
uint |
Returns the total number of files. |
totalitems |
uint |
Returns the total number of items. |
viewmode |
str |
Returns the current view mode in the file display. Values are largeicons, smallicons, list, details, power, thumbnails and tiles. |
As well as the above variables, you can also use evaluator functions like IsChecked and IsEnabled to query other information about the state of the Lister.
When generating executable commands, the evaluator can also access the values of the various external control codes as variables within the expression. For example, the current file path is available as the variable filepath.
Quotation marks are stripped by default from values supplied to the evaluator (e.g. allfilepath will not put quotes around any of the file paths). To enable quotes to be added, append #q to the variable name (e.g. allfilepath#q).
The return value from the evaluation expression should be a str.