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Getting Widget Style Properties

Until the move over to Gtk4, Gnocl is still built against the Gtk 2.21 libraries. One of the inconveniences of Gtk is getting and setting widget style settings which are considered to be set globally by the desktop style settings and not for the programmer to tinker around with. Needless to say, there are times when different defaults are preferred, largely to draw the users attention to 'something a bit different'.

The function gtk_widget_modify_font  is a convenience function to set the widget basefont as shown in this snippet from the button.c module, 

if ( options[baseFontIdx].status == GNOCL_STATUS_CHANGED ) {
 GtkWidget *label;
 label = gnoclFindChild ( GTK_WIDGET ( para->button ), GTK_TYPE_LABEL );
 PangoFontDescription *font_desc = pango_font_description_from_string ( Tcl_GetString ( options[baseFontIdx].val.obj ) );
 gtk_widget_modify_font ( GTK_WIDGET ( label ), font_desc );
 pango_font_description_free ( font_desc );
 }

Unfortunately, there's no direct retrieval convenience function in the Gtk API and the documentation on the matter is scant but, again from the button.c module, retrieving style properties can be done directly:

if ( idx == baseFontIdx ) {
GNOCL_DEBUG_LINE

GtkWidget *widget;
GtkStyle *style;

widget = gnoclFindChild ( GTK_WIDGET ( para->button ), GTK_TYPE_LABEL );
obj = Tcl_NewStringObj ( pango_font_description_to_string ( gtk_rc_get_style ( GTK_WIDGET ( widget ) )->font_desc), -1 );
}


There is an alternative api function gtk_style_get, as illustrated in this clip from treeList.c

if ( idx == treeLineWidthIdx ) {
 gint size;
 GtkStyle *style = gtk_rc_get_style ( para->view );
 gtk_style_get ( style, G_OBJECT_TYPE ( para->view ), "tree-line-width", &size );
 obj = Tcl_NewIntObj ( size );
 goto end;
 }


This won't work with base font as there's no object property!

The gtkstyle.h include file from the Gtk source code gives the structure containing all the details.


struct _GtkStyle
{
  GObject parent_instance;
  /*< public >*/
  GdkColor fg[5];
  GdkColor bg[5];
  GdkColor light[5];
  GdkColor dark[5];
  GdkColor mid[5];
  GdkColor text[5];
  GdkColor base[5];
  GdkColor text_aa[5]; /* Halfway between text/base */
  GdkColor black;
  GdkColor white;
  PangoFontDescription *font_desc;
  gint xthickness;
  gint ythickness;
  GdkGC *fg_gc[5];
  GdkGC *bg_gc[5];
  GdkGC *light_gc[5];
  GdkGC *dark_gc[5];
  GdkGC *mid_gc[5];
  GdkGC *text_gc[5];
  GdkGC *base_gc[5];
  GdkGC *text_aa_gc[5];
  GdkGC *black_gc;
  GdkGC *white_gc;
  GdkPixmap *bg_pixmap[5];
  /*< private >*/
  gint attach_count;
  gint depth;
  GdkColormap *colormap;
  GdkFont *private_font;
  PangoFontDescription *private_font_desc; /* Font description for style->private_font or %NULL */
  /* the RcStyle from which this style was created */
  GtkRcStyle *rc_style;
  GSList *styles;   /* of type GtkStyle* */
  GArray *property_cache;
  GSList         *icon_factories; /* of type GtkIconFactory* */
};



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