Help converting Dialog Units to Pixels

[Steve Mc Gregor]

I'm trying to convert dialog units to pixels using the win32 sdk
formula:

Local lTemp As Long
  Local baseX As Long
  Local baseY As Long
 
  lTemp = GetDialogBaseUnits
  baseX = LoWrd(lTemp)
  baseY = HiWrd(lTemp)

then to get the pixels:

PixelX = (DialogUnitX * baseX) / 4
  PixelY = (DialogUnitY * baseY) / 8

But when I used it to create a window with CreateWindowEx I get wrong
dimentions.

When I use the build in function DIALOG UNITS hDlg, x, y TO PIXELS xx,yy
don't work because my dialog wasn't created with DDT; but this function
get correct values.

Anybody can help me converting dialog units to pixels with Api calls.

Steve Mc Gregor

[Aldo Cavini]

steve, the matter is not easy - i also had problems and i still haven't the ideas clear.

first problem: dimensions declaration.
1- the createwindowex call specifies the window size - that is, with caption and frame included.
2- the dialog new specifies the client area, in dialog units.

second problem: the font
1- windows created via createwindowex use system_font by default.
1- ddt dialogs use ansi_var_font (i don't know is it is a windows or powerbasic default).

i'm almost sure getdialogbaseunits refers to system_font, which is wider than ansi_var_font. to get the exact font dimensions is not easy (see http://www.powerbasic.com/support/pb...ead.php?t=3617

hence the problems are: to know the caption and frame dimensions (use getsystemmetrics); to setup the desired font to the window; to get the correct base units.

i don't know if i'm right on all this stuff - i really hope some guy will give us a good explanation.

aldo

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[Chris Boss]

Steve;

Dialog Units are based on the average size of the font used by the
dialog. While working with the System font (default for dialogs)
isn't too bad since the character size is 8 x 16 pixels, DDT created
dialogs use the MS Sans Serif 8 PT Font (same as ANSI_VAR_FONT)
which has a character size of 6 x 13 pixels.

Since Dialogs units are calculated as follows :

CharWidth/4=XDialogUnit
CharHeight/8=YDialogUnit

You can see the difference between the System Font and the MS Sans Serif
font:

System Font:

8/4=2 pixels
16/8=2 pixels

Dialog Unit is 2 x 2 pixels.

MS Sans Serif Font (DDT):

6/4=1.5 pixels
13/8=1.625 pixels

Now the above only holds true when the end users system wide font
setting is : Small Fonts

If the end user's system is set to large fonts, the average font
size is large (System Font is 10 x 20 which still divides well).

GetDialogBaseUnits is only good for use with the System Font, so
is useless for DDT created Dialogs, but can be used with Windows
created using CreateWindowEx or Dialogs created using the API, which
use the System Font (no font defined in Resource template).




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[Steve Mc Gregor]

Using the following code I get correct the vertical dimentions:

  Local hDc   As Long
  Local TextM As TEXTMETRIC

  hDc = getDC(hParent)

  Call SelectObject(hDc, GetStockObject(%ANSI_VAR_FONT))
  Call GetTextMetrics(hDc, TextM)
  baseX = TextM.tmAveCharWidth
  baseY = TextM.tmHeight + TextM.tmExternalLeading

  Call ReleaseDC (hParent, hDc)

Then I use baseX and baseY values wit the formula:

  PixelX = (DialogUnitX * baseX) / 4
  PixelY = (DialogUnitY * baseY) / 8

Can anybody help.

Steve

[Steve Mc Gregor]

I finaly solved my problem with this code:

  Local hDc   As Long
  Local hFont As Long
  Local TextM As TEXTMETRIC

  hDc = getDC(hParent)
  hFont = GetStockObject(%ANSI_VAR_FONT)

  Call SelectObject(hDc, hFont)
  Call GetTextMetrics(hDc, TextM)

  baseX = TextM.tmAveCharWidth + 1 	' If I don't add a unit i get wrong X dimention
  baseY = TextM.tmHeight + TextM.tmExternalLeading

  Call SelectObject (hDc, hFont)
  Call ReleaseDC (hParent, hDc)

  xx = GetSystemMetrics(%SM_CXDLGFRAME) * 2     			    'Left and Right Borders
  yy = GetSystemMetrics(%SM_CYDLGFRAME) * 2 + GetSystemMetrics(%SM_CYSIZE)  'Top and Bottom Borders and Title Bar

then when you create a window:

  hMdi = CreateWindowEx(%WS_EX_MDICHILD, _
                              szClassName, _
                              "Tipo de cambio", _
                              %WS_CAPTION Or %WS_BORDER Or %WS_SYSMENU Or %WS_VISIBLE Or %WS_MINIMIZEBOX, _
                              %CW_USEDEFAULT, _
                              %CW_USEDEFAULT, _
                              (208 * baseX) / 4 + xx, _ ' This formula for X
                              (201 * baseY) / 8 + yy, _ ' This one for Y
                              hMdiClient, _
                              %NULL, _
                              hInst, _
                              ByVal %NULL)

It works perfectly in Win98 and WinNT.

Steve

[Semen Matusovski]

PixelX = (DialogUnitX * baseX) / 4 in C and PB can return different results.
In C a result is rounded according arithmetic rulles:
0.5 and greater = 1
In Pb: greater than 0.5 = 1

Example: 100 / 8 in C will be 13 (test API MulDiv); in PB - 12.
That's why I use something like (DialogUnitX * baseX) / 4 + 0.001 (unf. data type conversion)


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E-MAIL: [email protected]

[Lance Edmonds]

That is a good point - PowerBASIC uses Bankers Rounding. For values where the fractional part is exactly 0.5, become rounded toward the nearest even number. This gives the best overall distribution of rounded values, and PowerBASIC has always used this technique.

The addition of a very small (bias) value simply forces your code to rounds upward when the fractional part = exactly 0.5, regardless of the absolute value.

For example, 12.5 + 0.001 gets rounded to 13 because the small bias value prevented bankers rounding from being applied. Without this bias, 12.5 would have been rounded to 12.

BTW, this is documented in the manual.

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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Chris Boss]

Why not use the MulDiv API function mentioned by Semen ?

I use it for code that calculates Font heights based on the system
wide font setting (small/large fonts) !



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