Default Programs

I’m trying to figure out why my EasiWrite docs want to open with TechWrite. Or how to tell RISC OS that I want all jpeg files to open with SwiftJPEG. Is there a place to do this? All I have come across is the mimetypes file.

Hi Chris, this is generally covered by Configure > Boot > Look at. When an application gets looked at, RISC OS would use that as the default for opening a relevant file.

For example, on the RISC OS Direct bundle, SwiftJPEG is found at $.Graphics.SwiftJpeg.!SwiftJPEG. So if you drag-and-drop that application onto Look at, and then choose Set it will hopefully have that as default next time you boot.

What application is opening jpegs at the moment? If it’s in utilities you might have to move it out, as everything in there gets looked at.

The answer to this is rather complicated. When you doubleclick on a file of a given type the Filer broadcasts a Message_DataOpen message (see PRM 3-265) to all running tasks. If a task recognizes the file_type it replies to the Filer with a Message_LoadDataAck message, which means that the broadcast stops, and then the task is clear to have its way with the file. So which task gets to deal with the file rather depends on the order in which the Filer does its broadcast. If no task claims the file then the taskmanager executes the command given in the system variable Alias$@Runtype_xyz (where xyz are the hex digits of the filetype) with argument the file’s pathname. These system variables are often defined in an application’s !Boot file. Again, which application gets to set the system variable will depend on the order in which they are filer_booted. Mimetypes play no role in any of this – they did not exist when RISC OS got started.

I suspect that this topic has been rehearsed many times on this forum, and almost certainly with greater clarity.

To answer Julie’s question: !ChangeFSI opens all JPEG files by default. If I have !EasiWrite open, then my EasiWriter documents open just fine when double clicked. I had a feeling it was scanning applications in the folders. TechWriter is not in a folder, but EasiWriter is, so TechWriter gets seen first, which is what I was guessing was happening.

It’s one of those things I am trying to figure out as I have been using RISC OS more these days. Thanks for both responses, it is not just a simple answer!