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AlexeyMir (2002-10-29 11:04) [0]

...что такое Yield и как с ним работать. Я знаю только то что это наподобие ProcessMessage.

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Anatolyk (2002-10-29 11:17) [1]

в helpe такого я не нашел, но по аналогии с др. языками этот оператор позволяет выполняться другим процессам, т.е., я думаю, получается что-то вроде работы в фоновом или совместном режиме.
Вот раздел из Help для Clariona

YIELD (allow event processing)

YIELD

YIELD temporarily gives control to Windows to allow other concurrently executing Windows applications to process events they need to handle (except those events that would post messages
back to the program containing the YIELD statement, or events that would change focus to the other application).
YIELD is used to ensure that long batch processing in a Clarion application does not completely "lock out" other applications from completing their tasks. This is known as "cooperative
multi-tasking" and ensures that your Windows programs peacefully co-exist with any other Windows applications.
Within your Clarion application, YIELD only allows control to pass to EVENT:Timer events in other execution threads. This allows you to code a "background" procedure in its own execution
thread using the TIMER attribute to perform some long batch processing without requiring the user to wait until the task is complete before continuing with other work in the application. This is an
industry-standard Windows method of doing background processing within an application.

The example code on the next page demonstrates both approaches to performing batch processing: making the user wait for the process to complete, and processing in the background. Only
the WaitForProcess procedure requires the YIELD statement, because it takes full control of the program. Background processing using EVENT:Timer does not need a YIELD statement, since
the ACCEPT loop automatically performs cooperative multi-tasking with other Windows applications.

Example:

StartProcess PROCEDURE

Win WINDOW("Choose a Batch Process"),MDI
BUTTON("Full Control"),USE(?FullControl)
BUTTON("Background"),USE(?Background)
BUTTON("Close"),USE(?Close)
END
CODE
OPEN(Win)
ACCEPT
CASE ACCEPTED()
OF ?FullControl
DISABLE(FIRSTFIELD(),LASTFIELD()) !Disable all buttons
WaitForProcess ! and call the batch process procedure
ENABLE(FIRSTFIELD(),LASTFIELD()) !Enable buttons when batch is complete
OF ?Background
START(BackgroundProcess) !Start new execution thread for the process

OF ?Close
BREAK
END
END

WaitForProcess PROCEDURE !Full control Batch process
CODE
SETCURSOR(CURSOR:Wait) !Alert user to batch in progress
SET(File) !Set up a batch process
LOOP
NEXT(File)
IF ERRORCODE() THEN BREAK.
!Perform some batch processing code
YIELD !Yield to other applications and EVENT:Timer
END
SETCURSOR !Restore mmouse cursor

BackgroundProcess PROCEDURE !Background processing batch process
Win WINDOW("Batch Processing..."),TIMER(1),MDI

BUTTON("Cancel"),STD(STD:Close)
END
CODE
OPEN(Win)
SET(File) !Set up a batch process
ACCEPT
CASE EVENT()
OF EVENT:CloseWindow
BREAK
OF EVENT:Timer !Process records whenever the timer allows it
LOOP 3 TIMES
NEXT(File)
IF ERRORCODE()
POST(EVENT:CloseWindow)
BREAK
END
!Perform some batch processing code
. . .

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Anatoly Podgoretsky (2002-10-29 11:23) [2]

The Yield function is obsolete. This function is provided only for compatibility with 16-bit versions of Windows. In the Win32-based application programming interface (API), this function does nothing.

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