[cairo] PATCH cairo-www: fix memory leaks and other cleanup in Python FreeType example
Bryce Harrington
bryce at osg.samsung.com
Fri Jan 15 13:28:27 PST 2016
On Wed, Dec 23, 2015 at 02:24:50PM +1300, Lawrence D'Oliveiro wrote:
> >From 13596986985bd6a1fe60e18ed6adb1b41d36257c Mon Sep 17 00:00:00 2001
> From: Lawrence D'Oliveiro <ldo at geek-central.gen.nz>
> Date: Wed, 23 Dec 2015 01:23:19 +0000
> Subject: [PATCH] fix memory leaks and other cleanup in Python FreeType example
Thanks, pushed:
To git+ssh://cairographics.org/git/cairo-www
6df850a..3a0314a master -> master
> ---
> src/cookbook/freetypepython.mdwn | 140 +++++++++++++++++++++++++--------------
> 1 file changed, 92 insertions(+), 48 deletions(-)
>
> diff --git a/src/cookbook/freetypepython.mdwn b/src/cookbook/freetypepython.mdwn
> index a1a48de..5aea77f 100644
> --- a/src/cookbook/freetypepython.mdwn
> +++ b/src/cookbook/freetypepython.mdwn
> @@ -5,85 +5,129 @@ The following snippet uses Python's ctypes module to load a font file using Free
> and create a cairo font face from it, using the cairo-ft API that is not part of pycairo yet.
> The resulting cairo font face however can be used normally with pycairo.
>
> + #!/usr/bin/python3
>
> - import ctypes
> + 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 = ctypes.CDLL ("libfreetype.so.6")
> - _cairo_so = ctypes.CDLL ("libcairo.so.2")
> -
> - _cairo_so.cairo_ft_font_face_create_for_ft_face.restype = ctypes.c_void_p
> - _cairo_so.cairo_ft_font_face_create_for_ft_face.argtypes = [ ctypes.c_void_p, ctypes.c_int ]
> - _cairo_so.cairo_set_font_face.argtypes = [ ctypes.c_void_p, ctypes.c_void_p ]
> - _cairo_so.cairo_font_face_status.argtypes = [ ctypes.c_void_p ]
> - _cairo_so.cairo_status.argtypes = [ ctypes.c_void_p ]
> -
> + _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_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 = ctypes.c_void_p ()
> - if FT_Err_Ok != _freetype_so.FT_Init_FreeType (ctypes.byref (_ft_lib)):
> - raise "Error initialising FreeType library."
> -
> - class PycairoContext(ctypes.Structure):
> - _fields_ = [("PyObject_HEAD", ctypes.c_byte * object.__basicsize__),
> - ("ctx", ctypes.c_void_p),
> - ("base", ctypes.c_void_p)]
> -
> - _surface = cairo.ImageSurface (cairo.FORMAT_A8, 0, 0)
> -
> + _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
> -
> - # create freetype face
> - ft_face = ctypes.c_void_p()
> - cairo_ctx = cairo.Context (_surface)
> - cairo_t = PycairoContext.from_address(id(cairo_ctx)).ctx
> -
> - if FT_Err_Ok != _freetype_so.FT_New_Face (_ft_lib, filename, faceindex, ctypes.byref(ft_face)):
> - raise Exception("Error creating FreeType font face for " + filename)
> -
> - # create cairo font face for freetype face
> - cr_face = _cairo_so.cairo_ft_font_face_create_for_ft_face (ft_face, loadoptions)
> - if CAIRO_STATUS_SUCCESS != _cairo_so.cairo_font_face_status (cr_face):
> - raise Exception("Error creating cairo font face for " + filename)
> -
> - _cairo_so.cairo_set_font_face (cairo_t, cr_face)
> - if CAIRO_STATUS_SUCCESS != _cairo_so.cairo_status (cairo_t):
> - raise Exception("Error creating cairo font face for " + filename)
> -
> - face = cairo_ctx.get_font_face ()
> -
> + #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
>
> if __name__ == '__main__':
> -
> - face = create_cairo_font_face_for_file ("/usr/share/fonts/dejavu-lgc/DejaVuLGCSerif.ttf", 0)
> -
> + face = create_cairo_font_face_for_file("/usr/share/fonts/truetype/dejavu/DejaVuSerif.ttf", 0)
> surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 128, 128)
> -
> ctx = cairo.Context(surface)
>
> ctx.set_font_face(face)
> ctx.set_font_size(30)
> ctx.move_to(0, 44)
> ctx.show_text("Hello,")
> -
> ctx.move_to(30, 74)
> ctx.show_text("world!")
>
> del ctx
>
> surface.write_to_png("hello.png")
> + #end if
> --
> 2.6.0
>
> --
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