How can I modify the idf editor of EnergyPlus?

edit

The answer depends on what changes were made to the E+ source code. If changes to the source code do not affect the inputs for a specific E+ object (e.g., mathematical calculations were changed but the model inputs remain the same) then no other changes are required EXCEPT to replace the EnergyPlus.exe and EnergyPlusAPI.dll files in the root directory.

If the changes affect the model inputs (i.e., the inputs for an object as defined in the Input Data Dictionary (IDD) file), then the IDD file must be changed to reflect the new (added, removed, or modified) input fields. The changes to the IDD file will, in most cases, be understood by the idf editor.

Here's is a simple example of changes to an existing object in E+:

The version identifier object looks like this in an input file:

Version,8.3;

The definition of this object in the IDD file looks like this:

Version,
    \memo Specifies the EnergyPlus version of the IDF file.
    \unique-object
    \format singleLine
A1 ; \field Version Identifier
    \required-field
    \default 8.3

If you wanted to modify the information in the Version object, for example you wanted to add the date that this version was released, then the IDD file would be changed accordingly, and the source code would be changed to read the new input field.

Version,
    \memo Specifies the EnergyPlus version of the IDF file.
    \unique-object
    \format singleLine
A1 , \field Version Identifier
    \required-field
    \default 8.3
A2 ; \field Version Release Date
    \required-field
    \note Date Format: DD Month YYYY

And the new object in the input file might look like this:

Version,8.3, 23 July 2015;

After these changes were made in the E+ source code, the new IDD file would replace the existing IDD in the same directory where the EP-Launch.exe file is located. Then a modified input file, which includes the new field in the Version object, would be opened using EP-Launch by clicking the button "Edit - IDF Editor". If the changes to the IDD were able to be read by the IDF Editor, the modified input file would open without errors. If there were errors when using the new IDD and modified input file, then those errors would need correcting. Either errors were introduced in the IDD or modified input file, or the IDF Editor MAY need to be modified. In most cases, only changes to the IDD, source code, and input file are required. Only in very rare cases will the IDF Editor need to be modified.

There is specific syntax required when modifying the IDD file. For example, the use of \required-field means that specific input fields must be filled, otherwise an error will occur. Or if the developer wanted to note the meaning of the field, then that information is included using a \note entry. The \unique-object field (rare) means that only one Version object is allowed in an input file. The IDD syntax has many more \ fields, too many to mention here.