HOWTO: Use Custom System Colors Only When Your App Has Focus

ID: Q186062

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 6.0
Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SUMMARY

This article contains two examples for retrieving and setting system colors:

The first example is a demonstration of retrieving and setting the color of a specific aspect of the display.

The second example sets the colors of several items at once, and also manages resetting the colors when the application loses or gains focus.

MORE INFORMATION

To provide a consistent look to all Windows applications, the operating system provides and maintains global settings that define the colors of various aspects of the display. These settings as a group are sometimes referred to as a "color scheme." To view the current color settings, click Control Panel, double-click the Display icon, and then click the "Appearance" tab.

The following list shows the display aspects for which Windows maintains global settings:


   Name                  Description
   ----------------------------------------------------------------------
   ScrollBars            Scroll bar color
   Desktop               Desktop color
   ActiveTitleBar        Color of the title bar for the active window
   InactiveTitleBar      Color of the title bar for the inactive window
   MenuBar               Menu background color
   WindowBackground      Window background color
   WindowFrame           Window frame color
   MenuText              Color of text on menus
   WindowText            Color of text in windows
   TitleBarText          Color of text in caption, size box, and
                         scroll arrow
   ActiveBorder          Border color of active window
   InactiveBorder        Border color of inactive window
   ApplicationWorkspace  Background color of multiple-document interface
                         (MDI) applications
   Highlight             Background color of items selected in a control
   HighlightText         Text color of items selected in a control
   ButtonFace            Color of shading on the face of command buttons
   ButtonShadow          Color of shading on the edge of command buttons
   GrayText              Grayed (disabled) text
   ButtonText            Text color on push buttons
   InactiveCaptionText   Color of text in an inactive caption
   3DHighlight           Highlight color for 3-D display elements
   3DDKShadow            Darkest shadow color for 3-D display elements
   3DLight               Second lightest 3-D color after 3DHighlight
   InfoText              Color of text in ToolTips
   InfoBackground        Background color of ToolTips

The Windows API functions, GetSysColor and SetSysColors, allow these settings to be programmatically viewed and/or altered.

The GetSysColor API function is straightforward; you just pass a numeric value for the system setting whose color you seek, and the function returns the color.

However, the SetSysColors API function is not as straightforward. This function requires the use of three parameters:

The first parameter indicates the total number of system colors you are attempting to change.

The second parameter is an array of the numeric values for the display aspects you want to change.

The third parameter is also an array whose elements are the new colors for the display aspects defined by the first array. For example:


      Array Element   Array1                Array2
      ------------------------------------------------------------------

      0               COLOR_SCROLLBAR       vbRed
      1               COLOR_BTNSHADOW       vbGreen
      2               COLOR_HIGHLIGHTTEXT   vbBlue

If you use the settings in this table, you will set the scroll bar color to red, a command button's shadow to green, and highlighted text to blue.

Example 1

The following is a simple example of retrieving and changing one display color, the command button's caption, to a new, randomly generated color:

Create a new Standard EXE project. Form1 is created by default.

Add two CommandButtons to Form1.

Paste the following into the General Declarations section of Form1:


      Option Explicit

      Private Declare Function SetSysColors Lib "user32" (ByVal nChanges _
         As Long, lpSysColor As Long, lpColorValues As Long) As Long
      Private Declare Function GetSysColor Lib "user32" (ByVal nIndex _
         As Long) As Long

      Dim OriginalColor As Long
      Dim NewColor(0) As Long
      Dim IndexArray(0) As Long

      'Constant for screen aspects.
      Private Const COLOR_BTNTEXT = 18

      Private Sub Command1_Click()
         'Specify the aspect being changed.
         IndexArray(0) = COLOR_BTNTEXT

         'Randomly pick a new color.
         NewColor(0) = QBColor(Int(Rnd * 16))

         'Inform windows of the new color setting.
         SetSysColors 1, IndexArray(0), NewColor(0)
      End Sub

      Private Sub Command2_Click()
         'Specify the aspect being changed.
         IndexArray(0) = COLOR_BTNTEXT

         'Reset the original color.
         NewColor(0) = OriginalColor

         'Inform Windows of the new color setting.
         SetSysColors 1, IndexArray(0), NewColor(0)
      End Sub

      Sub Form_Load()
         'Retrieve current color for a button's caption.
         OriginalColor = GetSysColor(COLOR_BTNTEXT)

         Command1.Caption = "Change Color"
         Command2.Caption = "Reset Color"
         'Begin random number generator.
         Randomize
      End Sub

Save and run the sample.

Click Command1. With each click of this button, a random color is generated and set as the color of a CommandButton's caption.

Click Command2. The original color is restored.

Example 2

The following example demonstrates setting multiple display colors to a randomly generated set of colors in such a way that these new colors are only active while the sample application has focus.

NOTE: The following code sample uses a concept known as subclassing to allow you to detect when the WM_ACTIVATEAPP message occurs. This message occurs whenever an application gains or loses focus.

For more information on subclassing, please see the following article in the Microsoft Knowledge Base:

Q168795 : HOWTO: Hook into a Window's Messages Using AddressOf

WARNING: Failure to unhook a window before its destruction results in application errors, Invalid Page Faults, or data loss. This occurs because the new WinProc function that is pointed to no longer exists, but the window has not been notified of the change. Always unhook the subclassed window upon unloading the subclassed form or exiting the application.

This is especially important when you use Visual Basic to debug an application that includes subclassing. Clicking the End button or clicking End from the Run menu without unhooking causes an Invalid Page Fault and closes Microsoft Visual Basic.

Create a new Standard EXE project. Form1 is created by default.

Add a standard module to the project.

Paste the following into the General Declarations section of Form1:


      Option Explicit
      Sub Form_Load()
         'Begin random number generator
         Randomize

         'Store handle to this form's window.
         gHW = Me.hwnd

         'Call procedure to begin capturing messages for this window.
         Hook

         'Call procedure to generate the random new colors.
         GenerateRandomColors

         'Call procedure to save the original color settings.
         SaveOriginalColors

         'Call procedure to set the new colors as the ones in use.
         SetNewColors
      End Sub

      Private Sub Form_Resize()
         If Me.WindowState <> vbMinimized Then
            SetNewColors
         Else
            RestoreColors
         End If
      End Sub

      Private Sub Form_Unload(Cancel As Integer)
         'Call procedure to restore colors to their original.
         RestoreColors

         'Call subprocedure to cease hooking into messages.
         Unhook
      End Sub

Paste the following code into the module's code window:


      Option Explicit
      Declare Function SetSysColors Lib "user32" (ByVal nChanges As _
         Long, lpSysColor As Long, lpColorValues As Long) As Long
      Declare Function GetSysColor Lib "user32" (ByVal nIndex As Long) _
         As Long
      Declare Function CallWindowProc Lib "user32" Alias _
         "CallWindowProcA" (ByVal lpPrevWndFunc As Long, _
         ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, _
         ByVal lParam As Long) As Long
      Declare Function SetWindowLong Lib "user32" Alias _
         "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, _
         ByVal dwNewLong As Long) As Long

      Public Const WM_ACTIVATEAPP = &H1C
      Public Const GWL_WNDPROC = -4

      Public Const COLOR_SCROLLBAR = 0
      Public Const COLOR_BACKGROUND = 1
      Public Const COLOR_ACTIVECAPTION = 2
      Public Const COLOR_INACTIVECAPTION = 3
      Public Const COLOR_MENU = 4
      Public Const COLOR_WINDOW = 5
      Public Const COLOR_WINDOWFRAME = 6
      Public Const COLOR_MENUTEXT = 7
      Public Const COLOR_WINDOWTEXT = 8
      Public Const COLOR_CAPTIONTEXT = 9
      Public Const COLOR_ACTIVEBORDER = 10
      Public Const COLOR_INACTIVEBORDER = 11
      Public Const COLOR_APPWORKSPACE = 12
      Public Const COLOR_HIGHLIGHT = 13
      Public Const COLOR_HIGHLIGHTTEXT = 14
      Public Const COLOR_BTNFACE = 15
      Public Const COLOR_BTNSHADOW = 16
      Public Const COLOR_GRAYTEXT = 17
      Public Const COLOR_BTNTEXT = 18
      Public Const COLOR_INACTIVECAPTIONTEXT = 19
      Public Const COLOR_BTNHIGHLIGHT = 20

      Global OriginalColors(20) As Long
      Global NewColors(20) As Long
      Global IndexArray(20) As Long
      Global lpPrevWndProc As Long
      Global gHW As Long

      Public Sub Hook()
         'Establish a hook to capture messages to this window.
         lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _
            AddressOf WindowProc)
      End Sub

      Public Sub Unhook()
         Dim temp As Long

         'Reset the message handler for this window.
         temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)
      End Sub

      Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, _
         ByVal wParam As Long, ByVal lParam As Long) As Long
         'Check for the ActivateApp message.
         If uMsg = WM_ACTIVATEAPP Then
            'Check to see if Activating the application.
            If wParam <> 0 Then
               'Check to see if application is minimized.
               If Form1.WindowState <> vbMinimized Then
                  'Use custom colors.
                  SetNewColors
               End If
            Else
               'Application is DeActivating so restore normal colors.
               RestoreColors
            End If
         End If

         'Pass message on to the original window message handler.
         WindowProc = CallWindowProc(lpPrevWndProc, hw, uMsg, wParam, _
            lParam)
      End Function

      Public Sub RestoreColors()
         SetSysColors 21, IndexArray(0), OriginalColors(0)
      End Sub

      Public Sub SetNewColors()
         SetSysColors 21, IndexArray(0), NewColors(0)
      End Sub

      Public Sub GenerateRandomColors()
         'Randomly pick and assign new colors.
         IndexArray(0) = COLOR_SCROLLBAR
         NewColors(0) = QBColor(Int(16 * Rnd))
         IndexArray(1) = COLOR_BACKGROUND
         NewColors(1) = QBColor(Int(16 * Rnd))
         IndexArray(2) = COLOR_ACTIVECAPTION
         NewColors(2) = QBColor(Int(16 * Rnd))
         IndexArray(3) = COLOR_INACTIVECAPTION
         NewColors(3) = QBColor(Int(16 * Rnd))
         IndexArray(4) = COLOR_MENU
         NewColors(4) = QBColor(Int(16 * Rnd))
         IndexArray(5) = COLOR_WINDOW
         NewColors(5) = QBColor(Int(16 * Rnd))
         IndexArray(6) = COLOR_WINDOWFRAME
         NewColors(6) = QBColor(Int(16 * Rnd))
         IndexArray(7) = COLOR_MENUTEXT
         NewColors(7) = QBColor(Int(16 * Rnd))
         IndexArray(8) = COLOR_WINDOWTEXT
         NewColors(8) = QBColor(Int(16 * Rnd))
         IndexArray(9) = COLOR_CAPTIONTEXT
         NewColors(9) = QBColor(Int(16 * Rnd))
         IndexArray(10) = COLOR_ACTIVEBORDER
         NewColors(10) = QBColor(Int(16 * Rnd))
         IndexArray(11) = COLOR_INACTIVEBORDER
         NewColors(11) = QBColor(Int(16 * Rnd))
         IndexArray(12) = COLOR_APPWORKSPACE
         NewColors(12) = QBColor(Int(16 * Rnd))
         IndexArray(13) = COLOR_HIGHLIGHT
         NewColors(13) = QBColor(Int(16 * Rnd))
         IndexArray(14) = COLOR_HIGHLIGHTTEXT
         NewColors(14) = QBColor(Int(16 * Rnd))
         IndexArray(15) = COLOR_BTNFACE
         NewColors(15) = QBColor(Int(16 * Rnd))
         IndexArray(16) = COLOR_BTNSHADOW
         NewColors(16) = QBColor(Int(16 * Rnd))
         IndexArray(17) = COLOR_GRAYTEXT
         NewColors(17) = QBColor(Int(16 * Rnd))
         IndexArray(18) = COLOR_BTNTEXT
         NewColors(18) = QBColor(Int(16 * Rnd))
         IndexArray(19) = COLOR_INACTIVECAPTIONTEXT
         NewColors(19) = QBColor(Int(16 * Rnd))
         IndexArray(20) = COLOR_BTNHIGHLIGHT
         NewColors(20) = QBColor(Int(16 * Rnd))
      End Sub

      Public Sub SaveOriginalColors()
         Dim i As Long

         'Retrieve all current color settings.
         For i = 0 To 20
            OriginalColors(i) = GetSysColor(i)
         Next i
      End Sub

Save and run the project.

RESULT: When you start the sample application, the current colors are saved and new colors are randomly selected and assigned. A call is made to "hook" the window's messages. As you switch from this application to another, the colors are restored to their original settings. As you switch back to this application, the colors are again set to the random colors.

Note that if the machine crashes or if you close this application via the Windows Task Manager (by pressing CTRL+ALT+DEL), then the colors might be left in the randomly selected color scheme and would require resetting through the Windows Control Panel.

REFERENCES

For additional information, please see the following article in the Microsoft Knowledge Base:

Q168795 : HOWTO: Hook into a Window's Messages Using AddressOf

Additional query words: kbDSupport kbDSD kbSDKWin32 kbAPI kbHook sub-class kbVBp500 kbVBp600
kbVBp sub class

Keywords : kbGrpVB
Version :
Platform : WINDOWS
Issue type : kbhowto