#61 Crash when using fontconfig names for fonts

[Dov Grobgeld]

Using a fontconfig name, e.g. "Sans", as a file name
causes a crash in gtkplot canvas with the following
message:

** (test-simple:15802): WARNING **: Error, couldn't
locate default font. Shouldn't happen.

** (test-simple:15802): CRITICAL **:
gtk_psfont_get_font_description: assertion `font !=
NULL' failed
zsh: segmentation fault ./test-simple

Lines that caused the crash:

gtk_plot_canvas_put_child(GTK_PLOT_CANVAS(w_plot_canvas),
gtk_plot_canvas_text_new("Sans",
12, 0,
NULL, NULL,
FALSE,
GTK_JUSTIFY_CENTER,
"Intensity"
),
.10, .1, .20, .20);