This article was previously published under Q74299
To create a font in the Microsoft Windows graphical environment given onlythe required point size, an application must calculate the logical heightof the font because the CreateFont() and CreateFontIndirect() functions use logical units to specify height.
To describe a font to the user, an application can calculate a font's pointsize, given its height. This article provides the formulas required toperform these calculations for the MM_TEXT mapping mode. You will have toderive a new equation to calculate the font size in another mapping mode.
To calculate the logical height, use the following formula:
Point Size * LOGPIXELSY height = Internal Leading + ------------------------- 72
LOGPIXELSY is the number of pixels contained in a logical inch on thedevice. This value is obtained by calling the GetDeviceCaps() function with the LOGPIXELSY index. The value 72 is significant because one inch contains 72 points.
The problem with this calculation is that there is no method to determinethe internal leading for the font because it has not yet been created. Towork around this difficulty, use the following variation of the formula:
When an application calls the CreateFont() or CreateFontIndirect() functions and specifies a negative value for the height parameter, the font mapper provides the closest match for the character height rather than the cell height. The difference between the cell height and the character height is the internal leading, as demonstrated by the following diagram: