Bug fixing & stabilization

Since the previous update, focus has been mostly on improving the compatibility and stability of existing test applications through debugging, bug fixes and finishing some partially implemented features. This has so far had mostly effect on Excel, THINK Pascal and Fokker Triplane Flight Simulator:

Microsoft Excel 3.0 progress

Seems that Excel was complaining the out of memory error only because it could not locate the ‘PACK’ 6 resource (IntlUtils package). Adding a ‘PACK’ wrapper resource to System file, in similar fashion to the one which was added earlier for ResEdit as ‘PACK’ ID = 0, allowed this check to pass. After that a couple of new IntlUtils selectors were needed, with a couple file manager tweaks, and now Excel is able to start up successfully (albeit with a alert about not finding Excel, which can be passed).

It seems that a lot of tools and features are already functional, including basic worksheet creation, cell selection/modification, shape drawing, basic formatting etc. However, the most important feature, text input to allow entering data to worksheet cells, still requires TEDispatch to be implemented.

THINK Pascal 4.0 progress

One application which surfaced a lot of bugs and issues was THINK Pascal 4.0, here’s a rough summary of the issues found & ‘fixed’:

  • Reallocation of resources was not working properly in ChangedResource. Resource Manager did not save & restore active resource entry when measuring space available between current and next resource, which caused the new resource allocation in growth case to end up in wrong resource entry in the map (the next one was reallocated instead of current).
  • Removing name was attempted even if no name existed, causing resource names to get corrupted
  • RmveResource was not offsetting the types properly when removing the last instance of a given type.
  • The internal routine RGetResourceCount was trashing the resource entry pointer in resource manager’s stack state, causing some resources to be skipped altogether in iteration.
  • SetHandleSize was allowing locked blocks to move during the operation, which was explicitly told in Inside Mac documentation would not happen. This bug caused sometimes locked memory to move, with dereferenced pointers becoming invalid, causing crash during pascal code compilation.
  • A very rough approximation of MoveHHi was added. It works well enough to allow THINK Pascal to move resources out of the way to not prevent heap fragmentation from growing size of locked handles – but still causes sometimes fragmentation enough to surface this issue. However, this is for now enough to get the projects compile roughtly 2 to 3 times in one session before memory fragmentation kicks in and crashes the compiler.
  • The resource copy phase of THINK Pascal surfaced a bug in CountResources/GetIndResource, where CurMap was used instead of TopMap (CurMap should only be used when operating on 1-deep versions of the calls, Count1Resources/Get1IndResource). With this fix, the resource file copy phase succeeds.
  • Using “Transfer” command in THINK Pascal can be used to launch another app – in most cases, the application that was just compiled. However, the application zone teardown was – and still is – largely unfinished, having a number of issues. One that was fixed, was that resource manager attempts to release and purge all font caches with allocations in the application zone, which would be invalid upon launching the new program.
  • GetScrap trap had a minor issue, in which the case of hDest being nil it would crash, instead of just returning the scrap size as it was supposed to. This fixes the clipboard to (almost) work in THINK Pascal.

Now even a bit more complex programs can be compiled using THINK Pascal, for example one of Toni’s old games from as early as 1998. However, there are still minor glitches in various places:

  • Sometimes clipboard operation does not work on the first attempt.
  • Replacing existing application with “Build application” & replace dialog does not yet work because _Delete trap is still unfinished.
  • Sometimes text editing has very tiny minor selection glitches (when doing “Search again” in source code, where previous hit was selected and visible in area which was scrolled only little up, the old selection is left on when highlighting the new one).
  • Because resource map compaction is (still) unfinished, each time resources are updated and/or written in resource files, the file size grows indefinitely (by size of modified resource).
  • Compiling only works a couple times (2-3) on large projects, before heap fragmentation crashes the compiler.
  • The “Go” option does not yet work, because when running applications inside the THINK Pascal IDE, it does not actually launch a separate applications process for it. Instead, it loads the application “on top” of the pascal IDE, and in order to do this, it wraps a lot of its handlers to toolbox routines, and to do this, it manipulates the trap tables directly. This however assumes the toolbox trap table is located at 0xC00 on mac plus (0x75)-type machine, while it is currently located at 0xE00 (later machines). Because some currently used low memory globals overlap this area in non-compatible ways (for example, cursor device), they need to be adjusted a bit to behave differently on “Classic” type environment (like on real Mac Plus), and other way on later (slot-based / color-QD) environment.

Fokker Triplane Flight Simulator

It seems that the only issue causing Fokker Triplane to freeze upon starting new game was actually the lack of low-level interrupt handler emulation. The game attempted to override system VBL handler by adding its own VBL interrupt handler in the Lvl1DT low memory area containing the list of VIA’s Level 1 interrupt handler table, and as it was never called, caused the lock-up. The VBL, and 1-second timer, have now proper handlers in this low memory area, which is checked upon triggering the emulated VBL interrupt. This also includes the familiar performance optimization, where unpatched handlers skip the MixedMode interface with direct method call. It seems that with this change, the game is now fully playable with sound effects (although not thoroughly tested).

Full list of changes since last post

2019-11-16 04:08:45 +0200 • Lowlevel VIA interrupt handler for Fokker Triplane
2019-11-13 03:50:11 +0200 • Tweak SndNewChannel to not crash ResEdit          
2019-11-09 09:03:38 +0200 • Dummy OpenDeny/OpenRDeny (=>paramErr for local FS)
2019-11-09 07:51:53 +0200 • Workaround for mapping wideOpen Rgn in DrawPicture
2019-11-09 07:49:02 +0200 • Move File Manager commands to separate module     
2019-11-09 07:47:37 +0200 • Move SoundDriver test code to separate module     
2019-11-09 02:29:58 +0200 • Add dummy BitMapRgn trap for aWorm                
2019-11-06 05:40:10 +0200 • Respect port clipRgn in CopyBits                  
2019-11-06 04:31:42 +0200 • Fix edge cases in UnpackBits                      
2019-11-04 21:32:35 +0200 • If GetScrap argument hDest = nil, return only size
2019-11-04 11:31:38 +0200 • Clear font caches when closing res file w/ fonts  
2019-11-04 04:16:41 +0200 • Add IUMagString & improve Transliterate for Excel 
2019-11-04 03:09:38 +0200 • Fix Count…/GetIndResource to begin at TopMap    
2019-11-04 02:15:21 +0200 • Add memLockedErr enum missing from previous commit
2019-11-04 02:14:56 +0200 • (HACK) MoveHHi added - works, but not as in specs!
2019-11-04 02:12:08 +0200 • Fix SetHandleSize for locked blocks (don't move)  
2019-11-04 02:06:36 +0200 • Fix tail check in the zone check                  
2019-11-04 02:04:53 +0200 • Fix name allocation in AddResource                
2019-11-04 02:03:14 +0200 • StdFile: No "New folder" button in old dialogs    
2019-11-03 05:53:37 +0200 • More verbose heapcheck & optional free space debug
2019-11-02 18:13:37 +0200 • Fix possible TextEdit calibration memory move bug 
2019-11-02 17:40:30 +0200 • Fix resource map validation for maps with no names
2019-11-01 17:55:35 +0200 • Add dummy cstr2dec and pstr2dec selectors in Pack7
2019-11-01 17:54:15 +0200 • Don't trash ResourceEntry ptr in RGetResourceCount
2019-11-01 02:30:02 +0200 • Dummy IUMagWString & Transliterate(Text) for Excel
2019-11-01 00:43:41 +0200 • Add 'PACK' 3,4,5,6&7 mapping (Excel now starts up)
2019-10-31 21:33:21 +0200 • Resource fork compact placeholder code            
2019-10-31 01:01:48 +0200 • Fix RmveResource offset bug at last item of a type
2019-10-30 21:56:35 +0200 • Don't try to remove name if entry doesn't have one
2019-10-30 21:55:55 +0200 • Add map checks to Resource Manager calls for debug
2019-10-30 04:54:54 +0200 • Fix reallocation of resource in ChangedResource