[plt-scheme] Replace & Find in v4.1

Robby Findler wrote:
>> However, text selections made via the
>> "Find" button (as opposed to the Edit/Find Again menu item) are not
>> highlighted visibly; and the subsequent selection of the next match by
>> "Replace & Find" is not visibly highlighted, either.
>>     
> There should be. If the focus is in the window where you're searching,
> you should see the selection move. If the focus is in the search
> window, you should see a tan circle moving around inside the purple
> circles. Maybe that is just too light somehow?
>
>   
No, it really isn't being drawn in response to Find Again via button.  
Find Again via keyboard menuitem accelerator works as expected.

To repro:
1. Start a fresh DrScheme.  (Win XP SP2)
2. In the defns pane, type "one two three four five six seven"
3. Ctrl+f to go to the Find field
4. Type "three" - you'll see the proper purple oval appear in the defns pane
5. Without keyboard focus leaving rhe Find field, type Ctrl+g.  You'll 
see the light tan, indicative of selection in a text control that 
doesn't have focus.
6. Click with mouse back into the defns pane to clear the selection and 
give the pane focus
7. Now click the Find button.  It won't draw any text selection, either 
light tan or blue.
8. Pull down the Edit menu. All the Replace menu items are enabled, 
because in fact the text is selected -- just invisibly so.
9. You can prove the selection by mousing into the Replace field, typing 
"baz" or some such, and pressing the Replace button.  The invisibly 
selected "three" will be replaced with "baz."

Invisible selections is the only confusing thing.  Once you can see the 
selections, it'll be easy to figure out what the controls do.