Multiline overlay text

It would be convenient to keep external tools' formatting in overlay_text option. So that overlay_text = $(jhead $imv_current_file) gives multiline output as jhead does itself. Or to add support of some "formatting characters" such as "\n". Translation 0xA into '0x5C6E' of jhead's output I would do by an external program.

Thanks for great software!

Should be an easy enough change to the imv_canvas_printf function. I don't have the same coding time to devote to imv that I used to, but I'm happy to accept a patch for this.

It's actually wordexp that splits the overlay text according to shell input-field-separator (IFS) rules, not Pango.

Doing putenv("IFS="); right before the line

imv/src/imv.c

Line 1947 in eeaf5e3

if (wordexp(format, &word, 0) == 0) {

preserves the newlines in overlay text.

The manual for wordexp says that setting IFS is the only way to control this behavior. This seems like a dirty solution to me: setting IFS to an empty string will break many user shell commands. For example:

$ echo $(echo 'a    b') # prints 1 space, “a” and “b” are distinct arguments
a b
$ export IFS=
$ echo $(echo 'a    b') # prints 4 spaces, “a    b” is treated as one argument
a    b

So setting IFS doesn't seem acceptable to me, and I don't see a cleaner way to keep newlines while still using wordexp.

@eXeC64, would it make sense to add another shell expansion mechanism for overlay_text? We can keep it compatible with the current wordexp-based one or not.

One thing we could do is let the user run a shell command and use its output as overlay text. Interface-wise, we could trigger this by a special prefix in overlay_text parameter. For example, overlay_text = hello $(echo world) will trigger the current wordexp expansion, while overlay_text = sh:echo hello world will run echo hello world and use its output as overlay.

We could also use some library that implements wordexp functionality in a cleaner way. Quick googling didin't give me any though.

Let me know what you think.