更改平面滚动条的颜色（FlatSB_SetScrollProp 函数中的自定义调色板）

Question

One of my customers uses the standard flat scroll bars introduced in MSIE 4 inside the list/grid controls in his VB6 app. Now he wants to implement a dark theme in his app and needs to colorize these flat scroll bars respectively. The FlatSB_SetScrollProp WinAPI function allows us to change color parameters of flat scroll bars. I could easily specify the background color of the shaded shaft with the WSB_PROP_HBKGCOLOR/WSB_PROP_VBKGCOLOR values, but we need to change other colors - the background color of the scroll box, the color of arrows on the buttons, etc. FlatSB_SetScrollProp provides us with the ability to specify a custom palette for the scroll bars with the WSB_PROP_PALETTE value, but I couldn't find any working sample in the Internet showing how to do that. What I found were code snippets like this and this , but obviously they don't work. Can anybody provide a working sample for FlatSB_SetScrollProp with WSB_PROP_PALETTE?

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Some VB6 source code I used to play with palettes in flat scroll bars:

Private Type PALETTEENTRY
   peRed As Byte
   peGreen As Byte
   peBlue As Byte
   peFlags As Byte
End Type

Private Type LOGPALETTE
   palVersion As Integer
   palNumEntries As Integer
   palPalEntry(255) As PALETTEENTRY ' Enough for 256 colors.
End Type

Private Declare Function CreatePalette Lib "gdi32" (ByRef lpLogPalette As LOGPALETTE) As Long

Private Const WSB_PROP_PALETTE = &H800&

Private Declare Function FlatSB_SetScrollProp Lib "comctl32.dll" (ByVal hWnd As Long, ByVal Index As Long, ByVal newValue As Long, ByVal fRedraw As Boolean) As Long

Friend Sub SetCustomPalette()
   Dim LogPal As LOGPALETTE
   Dim hPal As Long
   
   LogPal.palNumEntries = 256
   LogPal.palVersion = &H300
   
   Dim iPalEntry As Long
   For iPalEntry = 0 To 255
      LogPal.palPalEntry(iPalEntry).peRed = iPalEntry
      'LogPal.palPalEntry(iPalEntry).peGreen = iPalEntry
      'LogPal.palPalEntry(iPalEntry).peBlue = iPalEntry
      'LogPal.palPalEntry(iPalEntry).peFlags = 4
   Next
   
   hPal = CreatePalette(LogPal)
   
   Dim lRes As Long
   lRes = FlatSB_SetScrollProp(m_hWnd, WSB_PROP_PALETTE, hPal, True)
End Sub

I checked the results of the CreatePalette and FlatSB_SetScrollProp calls - they were successful. I tried to fill only the peRed component or all R/G/B of a palette entry, tried all available values for peFlags, but nothing helped.

Perhaps, we also need to update the scroll bars in the target window after setting the palette or do something else to make it work. Any suggestions or ideas regarding this are welcome.

Answer 1

The FlatSB_SetScrollProp for WSB_PROP_VBKGCOLOR and WSB_PROP_HBKGCOLOR are really the only ones you can change for the scroll bar. The changing of the color palette will not change any other elements on the scroll bar if changed.

The usage of the palettes is not really recommended any further for applications and in newer window styles the flatsb APIs no longer work. If you are wanting to use a best fit color from your palette to the requested color you can use the GetNearestPaletteIndex to get the index of the entry for the logical palette and grab the RGB values from that to use as the color for the VBKGCOLOR and HBKGCOLOR.