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Date Posted: 09:42:08 02/22/01 Thu
Author: Michael Mount
Subject: Re: Keeping TWAIN interface loaded
In reply to: Michel 's message, "Re: Keeping TWAIN interface loaded" on 17:55:31 02/20/01 Tue

Hi Michel,

I tried as you suggested and seem to have cut the per scan time in half. I wanted to run this by you to make sure I didn't do anything stupid in the process since I'm not 100% certain of what everything does.

The BeginAcquire procedure was everything in Acquire up to and including ApplyOptions. I wrapped that all in a try..except block with the except portion calling EndAcquire.

The other two procedures follow:

procedure TScanner.AcquireWithSourceOpen( const AcquireEvent : TAcquireEvent;
const CallBackData : LongInt );
var
TwainUI : TW_USERINTERFACE;
begin
if FTwainData.SourceID.ID = 0 then BeginAcquire;
try
try
FillChar(TwainUI, SizeOf(TwainUI), 0);
TwainUI.ShowUI := FTwainData.ShowUI;
TwainUI.hParent := FTwainData.ParentHandle;

if not CallTriplet( @FTwainData.SourceId, @FTwainData.AppId,
DG_CONTROL, DAT_USERINTERFACE,
MSG_ENABLEDS, @TwainUI, nil, FTwainData.DsmEntry) then
raise ETwainError.Create('Unable to enable twain source.');

ProcessImages( AcquireEvent,
@FTwainData.SourceId, @FTwainData.AppId,
FTwainData.DsmEntry, CallBackData);

finally
CallTriplet( @FTwainData.SourceId, @FTwainData.AppId,
DG_CONTROL, DAT_USERINTERFACE,
MSG_DISABLEDS, @TwainUI, nil, FTwainData.DsmEntry);
end;
except
EndAcquire;
end;
end;

procedure TScanner.EndAcquire;
var
TwainUI: TW_USERINTERFACE;
begin
try
FillChar(TwainUI, SizeOf(TwainUI), 0);
TwainUI.ShowUI := FTwainData.ShowUI;
TwainUI.hParent := FTwainData.ParentHandle;

CallTriplet(
@FTwainData.SourceId, @FTwainData.AppId,
DG_CONTROL, DAT_USERINTERFACE, MSG_DISABLEDS, @TwainUI,
nil, FTwainData.DsmEntry);

finally
if FTwainData.SourceId.Id <> 0 then
begin
if not CallTriplet( nil, @FTwainData.AppId, DG_CONTROL, DAT_IDENTITY, MSG_CLOSEDS,
@FTwainData.SourceId, nil, FTwainData.DsmEntry) then
raise ETwainError.Create('Unable to close TWAIN data source');

FillChar(FTwainData.SourceId, SizeOf(FTwainData.SourceId), 0);
end;
end;
end;

I think that this closes the TwainUI after each call to AcquireWithSourceOpen but does not actually unload the drivers so the reentry time is significantly reduced. Does this look right to you? I removed the EnableWindow call because I didn't want to track the previous value across methods. Thanks for all your help.

- Mike

>Hi Mike,
<SNIP>
>I'll add this to the todo list. Let me know if you try
>this out.
>
>Best regards,
>
>Michel

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