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Small Fonts, Pixel & Twips

Multimedia meets databse. Normally we use an authoring system for the cartoons (Intro and Extro). That works pixel oriented and does not look like our normally fashioned Windows window. It's easy to tell VB not to use title and so on and it's easy to position the VB window exactly like the pixel map in the background. Nobody will recognize that tools have changed.

One little problem was to be solved, when we started a video sequence in a third window at a given position. Now we have three windows, one on top of the other. Any of the windows use its own optimized color palette. Sure - we had problems with palette shifting and we had to hide the window in the middle of the stack while playing the video. So we used the function GetScreenColors testing for palette size.

The function TestForSmallFonts (thanks 2 MSDN for GetDeviceCaps) was the result after looking for the error in graphic configuration and drivers on a test system. Most of the multimedia programs wont work if you use other fonts than small fonts. The reason is: they are mostly created using pixel oriented authoring systems. If you want to use real Windows objects, Twips and therefore so called logical lengths on printouts are our sizes to handle. Changing small fonts to other settings is changing logical lengths. This is, a text object displayed on systems with 640 x 480, small fonts has the same real size as with 800 x 600 and large fonts. 

I don't like CDs that ask me for restarting the system (you had to in former times when changing screen settings) we looked for a solution. LPX and LPY from TestForSmallFonts give us the number to resize pixel or twips oriented objects.

 

Declare Function GetDeviceCaps Lib "GDI" (ByVal hDC As Integer, _
	ByVal nIndex As Integer) As Integer
Declare Function CreateDC Lib "GDI" (ByVal lpDriverName As String, _
	ByVal lpDeviceName As String, ByVal lpOutput As String, _
	ByVal lpInitData As Any) As Integer
Declare Function DeleteDC Lib "GDI" (ByVal hDC As Integer) As Integer

Const BitsPixel = 12
Const Planes = 14
Public Const HORZRES = 8        '  Horizontal width in pixels
Public Const VERTRES = 10       '  Vertical width in pixels
Public Const VERTSIZE = 6       '  Vertical size in millimeters
Public Const HORZSIZE = 4       '  Horizontal size in millimeters
Public Const LOGPIXELSX = 88    '  Logical pixels/inch in X
Public Const LOGPIXELSY = 90    '  Logical pixels/inch in Y
Public Function TestForSmallFonts() As Boolean
  Dim NumWidth As Integer
  Dim hDC As Integer
  Dim X As Integer
  Dim LPX, LPY As Integer
  hDC = CreateDC("DISPLAY", "", "", "")
  LPX = GetDeviceCaps(hDC, LOGPIXELSX)
  LPY = GetDeviceCaps(hDC, LOGPIXELSY)
  X = DeleteDC(hDC)
  If LPX = 96 And LPY = 96 Then
     TestForSmallFonts = True
  Else
     TestForSmallFonts = False
  End If
End Function

Public Function GetScreenColors() As Long
  Dim NumColors As Long
  Dim hDC As Integer
  Dim X As Integer
  Dim PL As Integer
  Dim BP As Integer
  hDC = CreateDC("DISPLAY", "", "","")
  PL = GetDeviceCaps(hDC, Planes)
  BP = GetDeviceCaps(hDC,BitsPixel)
  NumColors = CLng(PL * BP)
  X = DeleteDC(hDC)
  GetScreenColors = NumColors
End Function

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