Visual Basic Programming Code Examples

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Change to priority level of the current process



Change to priority level of the current process

If you want to change the priority level of the current process then use the
code listed below. This is useful for processes which are not important and
may take a long time to complete, or when you want to speed a process up.

Option Explicit

Private Const THREAD_BASE_PRIORITY_IDLE As Long = -15, THREAD_BASE_PRIORITY_LOWRT As Long = 15
Private Const THREAD_BASE_PRIORITY_MIN  As Long = -2, THREAD_BASE_PRIORITY_MAX As Long = 2
Private Const THREAD_PRIORITY_LOWEST  As Long = THREAD_BASE_PRIORITY_MIN, THREAD_PRIORITY_HIGHEST As Long = THREAD_BASE_PRIORITY_MAX
Private Const THREAD_PRIORITY_BELOW_NORMAL As Long = (THREAD_PRIORITY_LOWEST + 1), THREAD_PRIORITY_ABOVE_NORMAL As Long = (THREAD_PRIORITY_HIGHEST - 1)
Private Const THREAD_PRIORITY_IDLE As Long = THREAD_BASE_PRIORITY_IDLE, THREAD_PRIORITY_NORMAL As Long = 0
Private Const THREAD_PRIORITY_TIME_CRITICAL As Long = THREAD_BASE_PRIORITY_LOWRT
Private Const HIGH_PRIORITY_CLASS As Long = &H80, IDLE_PRIORITY_CLASS As Long = &H40
Private Const NORMAL_PRIORITY_CLASS As Long = &H20, REALTIME_PRIORITY_CLASS As Long = &H100
Private Declare Function SetThreadPriority Lib "kernel32" (ByVal hThread As Long, ByVal nPriority As Long) As Long
Private Declare Function SetPriorityClass Lib "kernel32" (ByVal hProcess As Long, ByVal dwPriorityClass As Long) As Long
Private Declare Function GetThreadPriority Lib "kernel32" (ByVal hThread As Long) As Long
Private Declare Function GetPriorityClass Lib "kernel32" (ByVal hProcess As Long) As Long
Private Declare Function GetCurrentThread Lib "kernel32" () As Long
Private Declare Function GetCurrentProcess Lib "kernel32" () As Long


Sub Test()
    SetPriority THREAD_PRIORITY_LOWEST, IDLE_PRIORITY_CLASS
End Sub


'The SetPriorityClass function sets the priority class for the specified process
'This value together with the priority value of each thread of the process
'determines each thread's base priority level.
Sub SetPriority(ByVal lThreadPriority As Long, ByVal lClassPriority As Long)
    Dim hThread As Long, hProcess As Long
    'retrieve the current thread and process
    hThread = GetCurrentThread
    hProcess = GetCurrentProcess
    
    'Test the current priority
    'Debug.Print "Current Thread Priority:" + Str$(GetThreadPriority(hThread))
    'Debug.Print "Current Priority Class:" + Str$(GetPriorityClass(hProcess))
    
    'set the new thread priority to "lowest"
    SetThreadPriority hThread, lThreadPriority
    'set the new priority class to "idle"
    SetPriorityClass hProcess, lClassPriority
    
    'Re-test the priority
    'Debug.Print "Current Thread Priority:" + Str$(GetThreadPriority(hThread))
    'Debug.Print "Current Priority Class:" + Str$(GetPriorityClass(hProcess))
End Sub