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Fresco Type 5 Problems and their possible cure

One of the most annoying problems with Fresco is it's ability to give a "Type 5" error when you least expect it, causing Fresco to quit immediately and close any browser windows you may have had open. The annoying thing about this (from a support perspective) is it's reproducability factor; ie. Fresco works perfectly well on some computers, yet other people seem to get no end of problems.
It is my suspicion that the main cause is perhaps linked with individual computers which makes Fresco more fussy with particular setups. Because Acorn users are fond of 'tweaking' their systems, it's often impossible to tell how different users computers vary from the 'original' (ie. original Acorn designed) configuration.
This web page aims to give you some possible pointers you can look for in order to try to make your own setup more reliable.

The Fresco WimpScrap Cache

One common cause of problems when using Fresco is corruption of its cache. The cache is basically a store of files held locally on your hard drive which contain all the text and images of any web sites you've recently visited. If one of these files becomes corrupted, or left open, it might give problems next time you load Fresco - especially if Fresco crashed and exited untidily last time you used it.

The first thing I generally recommend is for people to clear the cache; To do this, quit Fresco if it's already loaded and open your hard drive filer window. There should be a directory called !Boot (on older machines, look for !Scrap). Open this directory by holding down shift and double-clicking on it. This should open another filer window containing a number of other files and directories. Double-click on the directory called 'Resources'. This opens yet another directory which should contain !Scrap. Hold shift down again and double-click on this to open it. Inside you should find a directory called 'ScrapDirs'. Double-click on this to open it. Inside this directory will be another directory, this time called ScrapDir (if your machine has a network card fitted and is networked to other machines you may also have a number of directories with random looking names starting with ID...)

Double-click on ScrapDir to open it. This will show what might be quite a full directory containing all your temporary scrap files. Things in here are safe to delete, as applications only store temporary files in here.

Firstly, delete all individual files (if there are any) but leave the directories alone. You'll generally find that there will be a number of directories, corresponding to various applications you have installed on your computer.

Once you've deleted all the individual files, locate the directory called 'Fresco'. This is the directory containing Fresco's cache. I would recommend deleting it in its entirety. Fresco will recreate it next time it loads anyway. This will delete Fresco's cache and may fix your problem.

If you find that the Fresco directory won't delete, then it's highly likely that a corrupt file is inside it - and this could be the cause of problems.

If you have my AntUtils or FresUtils or applications, this has a 'delete Fresco cache' facility built in, to automate the entire process above.

The Fresco File and Cache choice settings

Two more things to check are Fresco's actual cache settings within it's choices window. To verify these, load Fresco onto the icon bar and open it's choices window (MENU over it's icon). Click on 'Files and cache', which will open another window.

In the bottom half of this window are some 'Page cache' settings. Set the Limit disc cache to to 0 Kb. This allows Fresco to automatically manage its cache as big or small as it requires. Secondly, set the Maximum number of files to something quite large. I would recommend a minimum of 800 and optimally something like 2000.

Because a lot of web pages nowadays are quite large, containing many small graphics, you'd be surprised how many files are required just to render a single page (don't forget that every icon, image, photo, advertising banner etc is an individual file). Therefore a single page could conceivably contain more than 100 files.

The two toggle options below these two writable boxes tell Fresco whether to keep its cache on exit and/or to keep the history list on exit. If you turn off Keep cached files on exit then Fresco will delete its cache (described in the section above) every time you quit Fresco. This will save disc space and ensure that no potentially corrupted files remain from one session to the next. On the other hand, you won't be able to re-visit any previously visited sites without logging on again and refetching the page from the remote server. It's up to you - but you might like to experiment.

Hardware Considerations

- Timing Problems
Fresco seems more susceptible to 'timing' problems than other software. This could be due to the complexity of the multi-threading ability of the Ant Suite. Therefore if you have encountered timing problems in the past, this could be a contributing factor. If you have encountered problems you could try removing additional hardware (such as PC cards, if fitted) to see if that makes a difference to stability.

- Large Hard Discs
Fresco can cause problems with some types of large hard drive, especially when used with third-party hardware addons such as SCSI adapters. RISC OS versions prior to 4.02 had a number of bugs concerning filecore and hardware. To solve this, it's advisable to set the ADFSBuffers value to 0 (zero). You can find out what its existing value is by pressing f12 and typing the following

*status ADFSBuffersand pressing return. If the value returned is greater than zero, reconfigure it by typing the following;*configure ADFSBuffers 0and pressing return. You will now need to shutdown and restart your computer for the new value to become active.

- RISC OS 3.7 & StrongArm bugs
RISC OS 3.7 (as supplied with the StrongArm upgrade) had a couple of bugs in it, so you should make sure that you have ROMPatch 3 installed. If installed, this will be listed in your task display window, under the Dynamic areas section.

Things that can cause Type 5 errors

Most Type 5 errors tend to be caused by either running low on memory or by 'dodgy' Javascript. The most common cause by Javascript is to implement 'Rollover images'. These are the graphics you get on web pages which either hightlight or change when you move the mouse over them. They're a completely unessential gimmick but it seems that if Fresco hasn't correctly pre-cached the rollover image it can crash when executing the relevant Javascript. One solution would be to turn off Javascript when viewing such pages.

Another (again Javascript) cause of problems is when a web site attempts to open another page in a separate browser window, using a command such as window.open(). This command is generally handled quite well by Fresco versions 2.11 and above, but it's corresponding command to close the window - window.close() - can potentially cause worse problems. This is generally bad web design, but unfortunately we have to cope with it - until we can change the world! :-)

Another tip would be to try to avoid re-sizing the main browser window whilst Fresco is in the middle of rendering a complex page. Forcing a modified redraw in the middle of one might cause problems.

Possible Software Clashes

You may also find that some third-party software applications and utilities can cause problems when run in conjunction with Fresco.

One application which can cause problems with Fresco is the read/write version of !ArcFS - !ArcFSr/w. This appears to be down to a possible bug within !ArcFSr/w involving filer operations. One way to test if your copy of !ArcFSr/w exhibits the bug is to load !ArcFSr/w and then drop into BASIC (press d12 and type *BASIC), then enter the following command;

SYS "OS_FSControl",26 and press return. If you get a fatal error message saying "Internal error: abort on data transfer...." then the bug is present and you may encounter problems when using Fresco.

N.B. This only applies to the read/write version. The read-only version; !ArcFS appears to be ok.

One more application that I've received some comments about is EasyFontPro, but as I don't have this application I can't verify any claims, so please let me know if you have more information.

Other Longshot Ideas and Theories....

I'm convinced that many of the Type 5 errors are caused by untrapped 'memory overflow' problems. Perhaps caused by a slight inaccuracy in calculating the space required by images. I think if there is dramatic memory problem (such as only having 100K left and requiring to draw a 200K image) then Fresco will correctly issue an error message and cope. If however, memory is very marginal (such as only having 100K left and requiring to draw a 100K image) then Fresco might mistakingly try to allocate a memory block which might subsequently fail.

One rather nasty side effect of some Type 5 errors is that of leaving Fresco in a sort of 'limbo' state which might make it crash with a more serious crash in a few moments time. Even quitting and reloading Fresco doesn't mean that the page will be rendered correctly on a second attempt. The only real solution is to reset the machine and then try again.

This tends to point to Fresco leaving something in memory which is not cleared by quitting and reloading, but only on a machine reset. A possible area to examine here is the Dynamic Areas in RISC OS 3.5 or above. Fresco certainly seems to claim the same memory address on subsequent reloads, so I might try to develop a future AntUtils feature of killing Dynamic Areas after Fresco has crashed (and subsequently quit). Watch this space for further news.

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Last edit: 10th Apr 2016 at 1:55pm
(593 days ago)

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