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geda:pcb_fonts [2016/11/30 08:38]
cparker [Load Font]
geda:pcb_fonts [2016/12/06 09:03] (current)
cparker [File Load]
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 A font file can have one or more fonts defined in succession. A font file can have one or more fonts defined in succession.
 ====PCB File Format Changes==== ====PCB File Format Changes====
 +===Embedded Font Syntax===
 A single addition to the file format has been implemented. That's the Font directive that was described above. That directive can have two meanings. Fonts can be embedded in regular pcb files using the same syntax as above. The only caveat is that the font must be defined early in the file, between the styles and the layout data. A single addition to the file format has been implemented. That's the Font directive that was described above. That directive can have two meanings. Fonts can be embedded in regular pcb files using the same syntax as above. The only caveat is that the font must be defined early in the file, between the styles and the layout data.
  
 The Font directive can also be included without symbols. If it appears this way, then the argument is considered to be the PCB Default Font. This font is made the current font and is used for all reference designators and for any text objects that are not explicitly assigned a font. The Font directive can also be included without symbols. If it appears this way, then the argument is considered to be the PCB Default Font. This font is made the current font and is used for all reference designators and for any text objects that are not explicitly assigned a font.
 +
 +===Text Syntax===
 +There is also an addition to the text syntax. It's labeled in ''​parse_y.y''​ as ''​text_20161008_format''​. This is the same as ''​text_hi_format''​ with the addition of a second string field. The second string field is interpreted as the font. Here's the syntax definition:
 +<​code>​
 +text_20161008_format
 + /* x, y, direction, scale, text, font, flags */
 + : T_TEXT '​['​ measure measure number number STRING STRING flags '​]'​
 + {
 +                FontType * font = FindFont($8);​
 +                if(!font) Message(_("​Warning:​ Could not find font %s for text \"​%s\"​\n"​),​ $8, $7);
 + CreateNewText(Layer,​ font, NU ($3), NU ($4), $5, $6, $7, $9);
 + free ($7);
 +                free ($8);
 + }
 + ;
 +
 +</​code>​
 =====Actions===== =====Actions=====
 ====Change Font==== ====Change Font====
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 A note on the LoadFont function: the ParseFont function is still used, however, the details of how fonts are parsed in parse_y.y have been modified to create fonts in the appropriate library. After ParseFont reads the file and loads the data, the new font is appended to the end of the GSList that is the library. LoadFont exploits this to get the font pointer and set the name of the source file in the data structure. LoadFont then explicitly sorts the library to put the entry in alphabetical order. A note on the LoadFont function: the ParseFont function is still used, however, the details of how fonts are parsed in parse_y.y have been modified to create fonts in the appropriate library. After ParseFont reads the file and loads the data, the new font is appended to the end of the GSList that is the library. LoadFont exploits this to get the font pointer and set the name of the source file in the data structure. LoadFont then explicitly sorts the library to put the entry in alphabetical order.
 ====Unload Font==== ====Unload Font====
-The Unload Font Action is used for removing a font from the system library. ​It acts primarily as an interface to the UnloadFont function. This action first checks to see if the specified font is in the system library, and then checks to see if that font is used anywhere in the design.+The Unload Font Action is used for removing a font from the system library.\\ 
 +Syntax:\\ 
 +  * ''​UnloadFont(<​fontname>​)''​\\ Unload the font with the specified name. 
 +  * ''​UnloadFont(<​filename>​)''​\\ Unload the font loaded from the specified file name. 
 + 
 +The Unload Font Action ​acts primarily as an interface to the UnloadFont function. This action first checks to see if the specified font is in the system library, and then checks to see if that font is used anywhere in the design. 
 <​note>​The Unload Font Action will not allow a font that is used in the current design to be unloaded from the font library.</​note>​ <​note>​The Unload Font Action will not allow a font that is used in the current design to be unloaded from the font library.</​note>​
 +
 The Unload Font Action will also not allow the Default font to be unloaded, and although it should be redundant, checks to ensure that there is always at least one font in the system library. The Unload Font Action will also not allow the Default font to be unloaded, and although it should be redundant, checks to ensure that there is always at least one font in the system library.
  
 A note about the UnloadFont function. All of the sanity checking is performed in the Action, not in the function, because there are things that the system should be able to do that the user shouldn'​t. For example, the UnloadFont function is capable of unloading fonts from either the system library or the embedded library. This is to facilitate the closing of designs and the of the program. UnloadFont can be called with the font name "''​all''"​ which will enter a loop that will unload every font in the library. A note about the UnloadFont function. All of the sanity checking is performed in the Action, not in the function, because there are things that the system should be able to do that the user shouldn'​t. For example, the UnloadFont function is capable of unloading fonts from either the system library or the embedded library. This is to facilitate the closing of designs and the of the program. UnloadFont can be called with the font name "''​all''"​ which will enter a loop that will unload every font in the library.
 ====List Fonts==== ====List Fonts====
-The List Fonts Action was primarily for use as an introspection tool to evaluate the font system during development,​ however it may also find use facilitating testing. This action takes no arguments and writes to the message log the names of all of the fonts in the system library and the embedded library, the currently system font, the PCB font, and all of the fonts presently in use. +The List Fonts Action was primarily for use as an introspection tool to evaluate the font system during development,​ however it may also find use facilitating testing. This action takes no arguments and writes to the message log the names of all of the fonts in the system library and the embedded library, the currently system font, the PCB font, and all of the fonts presently in use. \\ 
 +Syntax:\\ 
 +  * ''​ListFonts()''​\\ List all fonts in use in the current design.
  
 A noteworthy function that is used here is the FontsUsed() function. This function builds a GSList of all the fonts used in the design. The list must be freed by the calling function. A noteworthy function that is used here is the FontsUsed() function. This function builds a GSList of all the fonts used in the design. The list must be freed by the calling function.
 +
 +Possible future upgrades/​expansions for this or a similar function:
 +  * list information about which library a font is in
 +  * take as an argument the name of a font and list the text objects that use that font
 =====Processes===== =====Processes=====
-====Startup====+====Startup/Shutdown==== 
 +When PCB starts up the font system has several command line options that are processed like normal options. These options include: 
 +  * ''​font-path''​\\ The path(s) in which to search for font files 
 +  * ''​font-file''​\\ The file name of the "​Default"​ font. This is loaded first to ensure that there is always at least one font in the system. 
 +  * ''​save-font-data''​\\ Save font information in pcb files. This is required in order for fonts to persist across saves. It will save the name of the font with the text object in the file. This option does not cause the fonts themselves to be included in the file (the ''​embed-font''​ option has that effect). Disabling this option will make the saved files backwards compatible with older versions of pcb. 
 +  * ''​save-symbols''​\\ This option causes the symbols of the current system font to be stored in saved files. This is the way that pcb has previously preserved a potentially modified font across saves.  
 +  * ''​embed-fonts''​\\ This option will embed the data for every font used in the design in the saved files. This ensures portability across systems that may have different fonts or different versions of the same font installed. 
 + 
 +The font system is initialized in the ''​settings_post_process''​ function (''​main.c''​). Here, the ''​font-file''​ is searched for in the ''​font-path''​(s) and loaded. Then the ''​font-path''​(s) are searched by the ''​ScanFontPaths''​ function (''​font.c''​) for any files that have a ''​.pcb_font''​ extension, and these files are read looking for font information.
 ====File Load==== ====File Load====
 +The loading of a pcb file has two parts: 1. the actual reading of data from the file and converting it into pcb data structures, and 2. applying policy to the loaded data. (1) is implemented using bison/flex in ''​parse_y.y''​ and ''​parse_l.l''​. (2) is implemented in ''​file.c''​ in the ''​real_load_pcb''​ function.
 +
 +===Reading Data From Files Into Data Structures===
 +==Font Data==
 +Font data is required to be located after style data and before object data in the pcb file (this is a requirement from before the font system that results from the definition of the file grammar). The variable ''​yyFont''​ acts as the global pointer to the current font. When font data (an embedded font or floating symbols) is found a new font instance is created in the appropriate library (depending on whether ''​yyPCB''​ is NULL, if not we're loading a pcb file, otherwise we're loading a font file), and subsequent symbols are added to that. If a new font is found, a new font instance is created and yyFont is updated to point at the new font. If only the font directive is found (no symbols), then the ''​DefaultFontName''​ field of the PCBType structure is updated with the name. (I've been inconsistent in the docs about referring to this font name as both the ''​PCBDefaultFont''​ and the ''​DefaultPCBFont''​)
 +==Text Data==
 +When text data is read from the file, it will either use the standard format, in which case the font pointer is initially set to NULL, or it will have a font specified, in which case the specified font is searched for in the font library (embedded library first). If the font is not found, then the font pointer is set to NULL. In post processing, any text object that has a NULL font pointer is set to the ''​DefaultPCBFont''​. If the ''​DefaultPCBFont''​ is NULL, then the font pointers remain set to NULL. This could happen if this is a pcb file from an older version that has no font information. When the font pointer of a text object is NULL, it is displayed using the system font instead. So, it's possible to completely ignore the font system, change the system font, and in doing so change the font of every bit of text on the board (including refdes).
 +
 +==Element Data==
 +The format of element data in pcb files doesn'​t presently include font information,​ so individual font cannot be stored for individual ref des. New elements are created via the ''​CreateNewElement''​ function (''​create.c''​) which adds text to the element via the ''​AddTextToElement''​ function (''​create.c''​). This function searches for the ''​PCBDefaultFont'',​ and assigns that if it's found, or NULL otherwise.
 +
 +===Post Loading Policy===
 +The policy defines how to handle objects that need fonts but were not assigned one during load. This is the magic that will hopefully make pcb "do the right thing" when loading older versions of pcb files.
 +
 +==System Font and Default Font Name==
 +The first (font related) thing pcb tries to do after loading all the data from a pcb file is figure out if it needs to change the current system font. If a ''​DefaultFontName''​ was specified, the system font is changed to this font. If we're dealing with an older file, there will be no ''​DefaultFontName''​ specified, but there still might be font data in the file (as loose symbols), and if there is, then it should be used. Symbol data gets loaded as a font in the embedded library, so if there are any fonts in the embedded library, the first one is set to be the system font. (Is this behavior okay if there are embedded fonts but no default font?)
 +
 +==Text Data==
 +After loading all data, 
 +
 ====File Save==== ====File Save====
 =====To Do List===== =====To Do List=====
 These are tasks and ideas related to the font subsystem that still need to be done, could be done, or are in progress: These are tasks and ideas related to the font subsystem that still need to be done, could be done, or are in progress:
 +  * Move work done in ChangeFontAction to separate function to isolate the work from the undo serial number increment
 +  * Check what happens when loading a font file if a ''​DefaultFontName''​ is specified
 +  * Add licensing info to font files
   * Add fonts to install (and figure out where they should go)   * Add fonts to install (and figure out where they should go)
   * Write test scripts   * Write test scripts
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   * Font preview in settings window   * Font preview in settings window
   * Character map for selecting non standard characters   * Character map for selecting non standard characters
-  * Add licensing info to font files 
   * User control of fonts in embedded library   * User control of fonts in embedded library
   * Save font(s) to a file   * Save font(s) to a file
   * "Font mode" saving of fonts to font files.   * "Font mode" saving of fonts to font files.
geda/pcb_fonts.1480513131.txt.gz · Last modified: 2016/11/30 08:38 by cparker