Flicker Control

Category: Controls - Edit Controls

Date: 02-16-2022

'When performing several actions, or actions on text that is not currently
'in the visible window, or when changing selections repeatedly - an edit
'control may flicker.  Disabling a control with WM_SetReDraw before taking
'actions, then turning enabling it after the actions have been taken can
'significantly improve performance.

'Primary Code:
SendMessage(hEdit, %WM_SETREDRAW, 0, 0)  'Turn off redraw for faster and smoother action
SendMessage hEdit, %WM_SETREDRAW, 1, 0   'Turn on redraw again and refresh

'Compilable Example:  (Jose Includes)
'This shows the impact of the flicker control statements. Press the first
'button and see the flicker. Press the second button and see the improved
'performance - no flicker and much faster!
#Compiler PBWin 9, PBWin 10
#Compile EXE
#Dim All
%Unicode=1
#Include "Win32API.inc"
Global hDlg As DWord, hEdit1 As DWord, hEdit2 As DWord

Function PBMain() As Long
   Local style&, buf$
   style& = %WS_TabStop Or %WS_Border Or  %ES_Left Or %ES_AutoHScroll Or %ES_MultiLine Or %ES_NoHideSel Or %ES_WantReturn
   buf$ = "This is sample" + $CrLf + "text for the" + $CrLf + "edit control."
   buf$ = buf$ + $CrLf + buf$ + $CrLf + buf$ + $CrLf + buf$ + $CrLf + buf$ + $CrLf + buf$
   Dialog New Pixels, 0, "TextBox Test",300,300,200,200, %WS_SysMenu, 0 To hDlg
   Control Add Button, hDlg, 100,"Flicker", 10,20,80,20
   Control Add Button, hDlg, 150,"Non-Flicker", 110,20,80,20
   Control Add TextBox, hDlg, 200,buf$, 10,50, 80,100, style&
   Control Add TextBox, hDlg, 250,buf$, 110,50,80,100, style&
   Control Handle hDlg, 200 To hEdit1
   Control Handle hDlg, 250 To hEdit2
   Control Add Label, hDlg, 300,"Flicker", 20,160,80,20
   Control Add Label, hDlg, 350,"Non-Flicker", 110,160,80,20
   Dialog Show Modal hDlg Call DlgProc
End Function

CallBack Function DlgProc() As Long
   Local i As Long, m&, n&, iResult&
   Dim iStart As Long, iEnd As Long, Result As String
   If CB.Msg = %WM_Command AND CB.Ctl = 100 AND CB.Ctlmsg = %BN_Clicked Then
      iStart = GetTickCount
      For i = 1 To 5000
         m& = Rnd(0,240)
         n& = Rnd(m&,240)
         iResult& = SendMessage(hEdit1, %EM_SetSel, m&, n&+1)
      Next i
      iResult& = SendMessage(hEdit1, %EM_SetSel, 1,2)
      iEnd = GetTickCount
      Control Set Text hDlg, 300, Format$((iEnd - iStart)/1000,3) & " seconds"
   End If
   If CB.Msg = %WM_Command AND CB.Ctl = 150 AND CB.Ctlmsg = %BN_Clicked Then
      iStart = GetTickCount
      SendMessage(hEdit2, %WM_SETREDRAW, 0, 0)    'Turn off redraw for faster and smoother action
      For i = 1 To 5000
         m& = Rnd(0,240)
         n& = Rnd(m&,240)
         iResult& = SendMessage(hEdit2, %EM_SetSel, m&, n&+1)
      Next i
      SendMessage hEdit2, %WM_SETREDRAW, 1, 0    'Turn on redraw again and refresh - may itself cause flicker in RichEdit..
      iResult& = SendMessage(hEdit2, %EM_SetSel, 1,2)
      iEnd = GetTickCount
      Control Set Text hDlg, 350, Format$((iEnd - iStart)/1000,3) & " seconds"
   End If
End Function

'gbs_00131
'Date: 03-10-2012

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