Microsoft KB Archive/186062

= How To Use Custom System Colors Only When Your App Has Focus =

Article ID: 186062

Article Last Modified on 7/13/2004

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APPLIES TO


 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Visual Basic 5.0 Control Creation Edition
 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition

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This article was previously published under Q186062



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.</li>  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

</li> Save and run the sample.</li> Click Command1. With each click of this button, a random color is generated and set as the color of a CommandButton's caption.</li> Click Command2. The original color is restored.</li></ol>

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:

168795 : How To 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.

<ol> Create a new Standard EXE project. Form1 is created by default.</li> Add a standard module to the project.</li>  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

</li>  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

</li> Save and run the project.</li></ol>

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.

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