Build a static image for the About dialog box background.gtk4

1 files changed, 111 insertions, 0 deletions

diff --git a/tools/about/ttf.py b/tools/about/ttf.py
new file mode 100644
index 0000000..eb6c027
--- /dev/null
+++ b/tools/about/ttf.py
@@ -0,0 +1,111 @@
+
+# Source: https://www.cairographics.org/cookbook/freetypepython/
+
+import ctypes as ct
+import cairo
+
+_initialized = False
+def create_cairo_font_face_for_file (filename, faceindex=0, loadoptions=0):
+    "given the name of a font file, and optional faceindex to pass to FT_New_Face" \
+    " and loadoptions to pass to cairo_ft_font_face_create_for_ft_face, creates" \
+    " a cairo.FontFace object that may be used to render text with that font."
+    global _initialized
+    global _freetype_so
+    global _cairo_so
+    global _ft_lib
+    global _ft_destroy_key
+    global _surface
+
+    CAIRO_STATUS_SUCCESS = 0
+    FT_Err_Ok = 0
+
+    if not _initialized:
+        # find shared objects
+        _freetype_so = ct.CDLL("libfreetype.so.6")
+        _cairo_so = ct.CDLL("libcairo.so.2")
+        _cairo_so.cairo_ft_font_face_create_for_ft_face.restype = ct.c_void_p
+        _cairo_so.cairo_ft_font_face_create_for_ft_face.argtypes = [ ct.c_void_p, ct.c_int ]
+        _cairo_so.cairo_font_face_get_user_data.restype = ct.c_void_p
+        _cairo_so.cairo_font_face_get_user_data.argtypes = (ct.c_void_p, ct.c_void_p)
+        _cairo_so.cairo_font_face_set_user_data.argtypes = (ct.c_void_p, ct.c_void_p, ct.c_void_p, ct.c_void_p)
+        _cairo_so.cairo_set_font_face.argtypes = [ ct.c_void_p, ct.c_void_p ]
+        _cairo_so.cairo_font_face_status.argtypes = [ ct.c_void_p ]
+        _cairo_so.cairo_font_face_destroy.argtypes = (ct.c_void_p,)
+        _cairo_so.cairo_status.argtypes = [ ct.c_void_p ]
+        # initialize freetype
+        _ft_lib = ct.c_void_p()
+        status = _freetype_so.FT_Init_FreeType(ct.byref(_ft_lib))
+        if  status != FT_Err_Ok :
+            raise RuntimeError("Error %d initializing FreeType library." % status)
+        #end if
+
+        class PycairoContext(ct.Structure):
+            _fields_ = \
+                [
+                    ("PyObject_HEAD", ct.c_byte * object.__basicsize__),
+                    ("ctx", ct.c_void_p),
+                    ("base", ct.c_void_p),
+                ]
+        #end PycairoContext
+
+        _surface = cairo.ImageSurface(cairo.FORMAT_A8, 0, 0)
+        _ft_destroy_key = ct.c_int() # dummy address
+        _initialized = True
+    #end if
+
+    ft_face = ct.c_void_p()
+    cr_face = None
+    try :
+        # load FreeType face
+        status = _freetype_so.FT_New_Face(_ft_lib, filename.encode("utf-8"), faceindex, ct.byref(ft_face))
+        if status != FT_Err_Ok :
+            raise RuntimeError("Error %d creating FreeType font face for %s" % (status, filename))
+        #end if
+
+        # create Cairo font face for freetype face
+        cr_face = _cairo_so.cairo_ft_font_face_create_for_ft_face(ft_face, loadoptions)
+        status = _cairo_so.cairo_font_face_status(cr_face)
+        if status != CAIRO_STATUS_SUCCESS :
+            raise RuntimeError("Error %d creating cairo font face for %s" % (status, filename))
+        #end if
+        # Problem: Cairo doesn't know to call FT_Done_Face when its font_face object is
+        # destroyed, so we have to do that for it, by attaching a cleanup callback to
+        # the font_face. This only needs to be done once for each font face, while
+        # cairo_ft_font_face_create_for_ft_face will return the same font_face if called
+        # twice with the same FT Face.
+        # The following check for whether the cleanup has been attached or not is
+        # actually unnecessary in our situation, because each call to FT_New_Face
+        # will return a new FT Face, but we include it here to show how to handle the
+        # general case.
+        if _cairo_so.cairo_font_face_get_user_data(cr_face, ct.byref(_ft_destroy_key)) == None :
+            status = _cairo_so.cairo_font_face_set_user_data \
+              (
+                cr_face,
+                ct.byref(_ft_destroy_key),
+                ft_face,
+                _freetype_so.FT_Done_Face
+              )
+            if status != CAIRO_STATUS_SUCCESS :
+                raise RuntimeError("Error %d doing user_data dance for %s" % (status, filename))
+            #end if
+            ft_face = None # Cairo has stolen my reference
+        #end if
+
+        # set Cairo font face into Cairo context
+        cairo_ctx = cairo.Context(_surface)
+        cairo_t = PycairoContext.from_address(id(cairo_ctx)).ctx
+        _cairo_so.cairo_set_font_face(cairo_t, cr_face)
+        status = _cairo_so.cairo_font_face_status(cairo_t)
+        if status != CAIRO_STATUS_SUCCESS :
+            raise RuntimeError("Error %d creating cairo font face for %s" % (status, filename))
+        #end if
+
+    finally :
+        _cairo_so.cairo_font_face_destroy(cr_face)
+        _freetype_so.FT_Done_Face(ft_face)
+    #end try
+
+    # get back Cairo font face as a Python object
+    face = cairo_ctx.get_font_face()
+    return face
+#end create_cairo_font_face_for_file