Documentation: Fonts [Remove Frame]
Type faces in FOX are manipulated using FXFont objects. To provide a consistent look and feel for all applications, most FOX widgets normally share one common font object, which is automatically adopted when the widget is constructed. However, a widget's font is readily changed using the setFont() member function. Changing fonts on widgets will automatically cause an adjustment in layout so that the new size of the widget is accomodated.
As with most other resources such as FXIcon and FXCursor etc., building FXFont objects also takes two steps:- construction of the client-side part of the font object, followed by creation of the corresponding server-side part. During construction, all necessary information is supplied to the FXFont object so that the desired font may be located and loaded into memory during the creation. In most cases, the font objects are automatically created when the widget that uses it is being created. If you have constructed a new FXFont object later on, however, you may have to make a call to the font object's create() member function to make sure the font object is fully initialized. As different computer systems may have different fonts, it is possible that the specific font your application needs may not be available. Since you probably still would like this application to run anyway, alternative fonts must be found.
FOX supports mechanisms to localize fonts which are ``close'' [in some easthetic sense] to the desired font, so that applications will typically not fail simply because of missing fonts. Keep in mind, however, that the information you supplied to the FXFont contructor may not accurately reflect the font that is actually being used in your application.
Also note that information about a font will not be available until after the font has been created using create().
Using Font Objects
Using fonts is really very easy. For example, to build a Button Control with a different Font for the caption, you would use the following C++ code:
FXButton *button = new FXButton(parent,"&Caption"); FXFont* captionfont = new FXFont(app,"times",24); button->setFont(captionfont);
This statements will create a Button with caption ``Caption'' and use a font of 24 points Times. Note that in this case we assume that the captionfont will be created in the process of creating the Button; if you were to change fonts after the application has already started running, you would want to call captionfont->create() to make sure the font resources are created. Also note that font objects may be shared between several controls; thus, you don't have to create a different font object for each control [unless of course you want to use a different font!]. In the above example, we have taken default values for many parameters influencing the choice of font. The above call is actually equivalent to:
FXFont* captionfont = new FXFont(app, "times", 24, FONTWEIGHT_NORMAL, FONTSLANT_REGULAR, FONTENCODING_DEFAULT, 0);
That is to say, construct a font with face name ``times,'' 24 points, normal weight [not bold], no italics, and use whatever character encoding is available for this font; finally, the zero (0) indicates there are no hints.Besides the above platform-independent font constructor, FXFont also has an alternative constructor which is only applicable to the X11 Window System; this method bypasses the font matching algorithm. Assuming that our display was 75 dots per inch (dpi), the alternative method of contructing fonts using the X11 font string would have been:
FXFont* captionfont = new FXFont(app,"-adobe-times-medium-r-normal--24-240-75-75-p-124-iso8859-1");
Besides being harder to remember, this method would not port over very well to other systems, or systems where this particular font is not available. However, there are a few reasons why sometimes you may need this method:
Font Matching and Substitution
In order to be able to write applications which may be ported to a large
variety of computer systems and software environments, it is necessary
to make sure that the absence of certain fonts is handled gracefully.
The FXFont implementation offers a number of benefits that allow you to get your application running under a wide variety of environments, even on systems where very few fonts have been installed:
Before trying to acquire a list of available fonts for a certain type face,
the FXFont implementation first tries a substitution for the type
face name. The standard FOX registry is used to make this
association. The substitute font is found in the section FONTSUBSTITUTIONS
of the registry.
For example, the following fragment decribes the registry settings which would replace ``swiss'' by ``helvetica'' and ``new century schoolbook'' by ``courier'':
[FONTSUBSTITUTIONS] swiss = helvetica new century schoolbook = courier
Thus, you can easily give a FOX application another font even if you might not have the source code around!
After having substituted the type face name, the FXFont implementation tries to find the font from the given type face that best matches the parameters and hints. Parameters or hints which are given a ``don't care'' value are considered matched. For example, if you specify FONTWEIGHT_DONTCARE for the font weight, all font weights would match and the resulting font will be based on other parameters.
Not all parameters have the same priority as far as matching goes; the importance of the parameters is as follows:
After having tried all the members of the specified type face, if no match is found at all, the FXFont implementation tries a number of other common fonts, based on additional hints:
If all the above failed, yet there is at least one font on your system, then you should report this problem on the FOX mailing list...
Since current-day analog monitors can stretch and shrink the visible field of the display, the actual resolution is typically not exactly 75dpi or 100dpi. To get a font's point size as close to the desired pointsize as possible, FOX adjusts for the actual screen dpi relative to the font's dpi.For example, suppose we have a font such as:
This font is a 12-point font designed for a 75 dpi device. If your monitor however is set to display 90 dpi, the font would be too small. The implementation can correct for this by multiplying the font's point size by (75/90) which means visually this font would actually be more like 10-points on your monitor. Thus, to get a font designed for 100 dpi to display as 12 points on your monitor, we should search for a font which is slightly larger than 12-point; to be exact, we should be looking for a font (90/75)*12 = 14.4-point font.
On many systems such as work stations, the machine is shipped with accurate information about the particular monitor supplied with the system; on such systems, the font implementation of FOX will correctly determine the right resolution to use. On PC's however, hardware is mixed and matched from different sources, and the reported screen sizes may be incorrect, causing fonts to bigger or smaller than requested.
When the system reports the wrong resolution, you can easily correct that by setting the resolution yourself using the registry database. On my system, for example, the XFree86 X Server reports 75 dpi, while I really have 100dpi. So I change my registry database as follows:
[SETTINGS] screenxres = 100 screenyres = 100
These entries need to go into the ``Desktop'' file so that all FOX programs will be aware of this, regardless of vendor or application name. For more about the registry, see the section on FXRegistry.
|Copyright © 1997-2016 Jeroen van der Zijp|