CHUI files

Description

The Infinity Engine gui is represented through a combination of these CHUI files and the MOS and BAM files which are used for their visual representation. Roughly, the gui is composed of multiple "windows", any number of which can be activated at once; each window can have any number of "controls". A "window" can have a MOS file as its background, or it can have no background. A "control" has various parameters, one of which typically includes BAM files, along with cycle and frame indices to choose which frame of the BAM file to display.

CHUI file versions

• V1: Baldur's Gate, Planescape: Torment

CHUI V1

Overall structure

• Header
• Windows
• Control table
• Controls

CHUI V1 Header

CHUI V1 Windows

An interesting note about this structure. In BG, all of the CHUI files except for 1 exhibit a particular structure in their windows. (They are all 28 bytes in length.) This one exceptional file exhibits a 36-byte structure, which is essentially the 28-byte structure, except with an 8-byte descriptive name prepended. The question this raises is whether that exceptional file is a glitch or part of some additional unseen structure. It appears from the analysis I've done that the 36-byte file is spurious and was unintentionally included (i.e. the format of the file changed internally, and the version number didn't change. Then, when they were packing up the BIF files, they unintentionally included some files which were no longer needed. This wouldn't be too surprising, since there were BG files included in the Torment packaging, too.) Anyway, so the structure as presented here does not account for the spurious file. It is possible to create a routine to handle both types, simply because (offsetCtlTab - offsetWindows) / numWindows should be equal to the size of the window struct. But it's not clear that this is necessary. Most of the routines in BG are hard-coded to a 28-byte long window structure.

CHUI V1 Control table

The different types of controls are all different sizes. Thus, in order to quickly set up the pointer structure after the data file is loaded, they need to store the offsets of each control. For some reason, they also store the size of the control structure. This is mystifying, since they almost never move things around in memory -- typically, they load the resource as one chunk, and then setup pointers to the appropriate bits, never having moved anything or done any more memory allocation than necessary. Actually a pretty fast way to deal with resources, although I suspect that performance might suffer at times from non-aligned memory access of commonly used fields.

CHUI V1 Controls

The different types of controls have different layouts; however, there is a common format for the first portion of the control, which dictates its position, its type, and a few other things.

The types of controls which I have been able to figure out are:

• type 0: buttons/toggle buttons/pixmaps
• type 2: slider controls
• type 3: text edit field
• type 5: text area (optionally scrolled)
• type 6: label? static text field?
• type 7: scroll bar

fields common to all control types

CHUI V1 Controls: type 0: buttons/toggle buttons/pixmaps

This is a simple type of control. It has an associated BAM file, a 'cycle number', which selects which cycle in the BAM to use frames from, and several associated frame numbers. For static pixmaps, clicks are ignored, and the pressed/unpressed frame indices are the same. For buttons, there is a pressed and an unpressed frame. Now, a caveat about this format. I believe that I have figured out the format of this type of control; however, I have found a file which does not quite appear to follow this format. This is the same file which is mentioned above whose windows appear to follow a different format from those of every other CHUI file in the game. For this reason, it seems highly likely that this is not a valid data point for disproving this format; however, keep this in mind while you examine this format.

CHUI V1 Controls: type 2: slider controls

The vast majority of the fields in this control are unknown... I know what it does, and vaguely see how it could do it in a manner consistent with what I know, but...

CHUI V1 Controls: type 3: text edit field

Text edit fields, similar to that used for multi-player chat mode, typing in the name of your player, or entering cheat codes. Again, this control is mostly mysterious, still. Some of the unknown bytes must code for the cycle number and frame number in the BAM file to use for the cursor graphic, but I don't know which.

CHUI V1 Controls: type 5: text area (optionally scrolled)

Just about any text with a scrollbar you see in BG uses this control type. For instance, scrolled character sheet, or inventory item description. It is not entirely clear why there are two fonts and 3 colors involved here; I can't shed too much light on this, except to mention that in many cases, one of the fonts is the "illuminated manuscript" style font that is used for the first character of text in some dialogs. Beyond that, it's still a mystery.

CHUI V1 Controls: type 6: label/static text field (?)

Many static labels use this. It may have more functionality than that, but that's all I know about. (i.e. I believe it ignores input and is only used for outputting text, primarily labels

CHUI V1 Controls: type 7: scroll bar

These scroll-bars are usually attached to a text-area. Sometimes, though (for instance, the save game screen), they are not.

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