TIP #145 Version 1.1: Enhanced Tk Font Handling

This is not necessarily the current version of this TIP.

Abstract

TIP #64 suggests some improvements to font handling under windows. However, not all of this TIP appears to have been implemented and I believe this can be done better using the Tk named fonts mechanism.

Rationale

Windows, and no doubt MacOS as well, provide a number of system defined fonts. These are fonts that may be configured by the end user and that all applications are expected to use. The list includes the menu font, the caption font, the tooltip font and others. Some of the special fonts have been given symbolic names but these are not available to dynamic inspection. This TIP proposes to make these fonts available using the named font mechanism as used by the font create command. This has some significant advantages. The set of special font names becomes available to the programmer using the font names command. The font configuration is available using the font configure command. Also there is already a scheme in place to update all widgets using a named font when that fonts configuration changes. It is now a simple matter of re-defining the system fonts on receipt of the WM_SETTINGCHANGE message to have Tk properly reflect changes to the system-wide font selection.

Proposed Changes

The named font creation routine CreateNamedFont needs to be exposed on the internal API as TkCreateNamedFont. Also, the code used to delete a named font should be factored out into a function, TkDeleteNamedFont.

A TkWinSetupSystemFonts function is to be created which obtains the font description for the system fonts and calls TkCreateNamedFont appropriately. This needs to be called during font package initialization. The fonts are obtained using the Win32 SystemParameters API and the set of defined stock object identifiers used with GetStockObject.

The toplevel Windows message message handler function WmProc must handle the WM_SETTINGCHANGE message by calling the TkWinSetupSystemFonts function. This must call TkDeleteNamedFont and then TkCreateNamedFont to properly re-define the font and to propagate this change to all Tk widgets concerned.

Cross-Platform Concerns

It seems likely to be useful to ensure that aliases are available for each platform for the set of system fonts. This is currently done for the Tk cursors and helps to ensure that a script written for one system will usefully operate on another platform.

Implementation

http://sf.net/tracker/?func=detail&aid=780617&group_id=12997&atid=312997

Copyright

This document is placed in the public domain.

This is not necessarily the current version of this TIP.