I recently asked about workarounds for the very poor performance of clip
regions in MI Pro v 5.5 (v earlier and later versions).  I received a number
of excellent replies including:

Sheila Quan and Jason Adam suggested large rectangles with a centre cutout
for the area of interest.  Jason's recipe was :

Instead of making 4 rectangles, try this
1. make one rectangle over the area you want to show.
2. Zoom out and make a much larger rectangle over this one.
3. Select the large rectangle and choose Object>Set Target
4. Select the smaller rectangle (hold ctrl while clicking to select
hidden/buried objects) and choose Objects>Erase.
5. Select the small rectangle again and delete it.
You should be left with one large rectangle with a hole in it displaying the
map area you desire.
For convenience, you may want to Save Cosmetic Objects to a New table (call
it something like MapClipArea).  Then you can modify the display properties
of that new table as you would any other layer, as well as move it up and
down the layer stack should you desire.

Juanse Barros suggested I could return to v 4.5 and use Bill Thoen's recipe
for making my version 5 MapBasic  .mbx files compatible with earlier
versions of MI (will supply on request).

Derek Snyder of MapInfo noted that this problem has been dealt with in v 6.0
(though I'm not particularly impressed with buying a second upgrade in 6
months for the sole purpose of regaining functionality that was present in
earlier versions):

Clip Region is a display-time action that we wish to have performed as fast
as possible.  In MI Pro 6.0, we implemented a version of Clip Region and
uses Microsoft Windows-based clipping.  This has proved to be far faster
than even the old MI Pro 5.0 Clip Region.  It also has some added benefits,
such as the ability to clip text, which was not possible with the older
scheme.  However, the user still has options to either use the old scheme,
or to use a Microsoft Windows-based clip region that mimics the old scheme
(i.e., it doesn't clip text).

Thanks for all your help,

Peter Strain
Bedford Institute of Oceanography
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