Calling external command (text editor) for editing string properties

[WeirdConstructor]

I have a feature request, which would possibly benefit many programmers and extensive NPC dialogue writers:

Make it possible to configure an external command to be called for editing text/string properties.

The use case: Make it possible to use a proper text editor (VIM, Emacs, Sublime, Atom, Notepad++, ...) with syntax highlighting for Scripts that are local to the map or the object. It would also make any other form of text editing much more comfortable to do.

This is so useful, that I might hack it into Tiled myself someday, but I might not have the time to execute the change properly for a pull request and I am currently involved too much in other projects. Maybe someone else likes this idea so much, that he is also urged to implement it before I get the chance.

Preparations

• Add global setting/preference for configuring external editor command, add '%' or something similar for replacement by some temporary file name. Contents could/would be something like "gvim --remote-tab-wait %".
• If an external editor is configured either replace the "..." button for editing a string property or add a new button next to "..." eg. with a label like "e".

Algorithm for that button click

1. contents of the string property is written to a temporary file (with random filename, which is eventually deleted after the text editor exits). (If QString is internally used, store the contents UTF-8 encoded.)
2. run the external editor command, in case an error value is returned signal an error to the user (typical error confirmation dialog) and delete the temporary file.
3. if the editor was successfully started, start a timer, which regularly checks if the modified time of the temporary file changed. If it changed, update the contents of the text property.
4. once the editor finally exits, check again if the temporary file changed, and replace the string property if necessary.
5. delete the temporary file to prevent the temp directory from clobbering.

Possible Future Extensions

• I read that nested/structured properties like arrays or whole map/array trees are a feature request. For those I could imagine storing them in the temporary file as (pretty printed) JSON for editing with an external editor. Possibly a JSON-Structure editor or simply a text editor.
• Add some way of specifying the content type of string/text properties, to be able to generate the temporary files with a fitting extension (.py, .lua, .json, .xml) so the external editor can better apply syntax highlighting. (For VIM you can use modeline magic to set the syntax highlighting, but other editors might not have something similar.)
• If there are content types for string properties, make it possible to call a different editor for each. (LibreOffice Calc for .csv for instance.).
• Add a similar buttons close to tilesets (mabye in the toolbar), to run an external image editor (Aseprite, Gimp, Photoshop, ...).

[bjorn]

I quite like the idea. Implementation-wise, this should probably integrate with the Custom Commands functionality. We can also look at how Qt Creator implemented this since their "External Tools" settings already have similar options.

Unfortunately there is no easy way to add content type information to string properties, but if this is done by setting up external tools then the user could at least set up different tools if he wants to use it for different kinds of data.