Specify XCB types more carefully to fix crashes on 32-bit systems

[mitya57]

See the following bugs:

• https://bugzilla.redhat.com/show_bug.cgi?id=1478616
• http://forums.purebasic.com/english/viewtopic.php?f=23&t=70854

[grulja]

How do I verify these changes are correct? I didn't write this part of code and to be honest I don't even know what is this used for.

@MartinBriza do you know?

[mitya57]

This part is used for setting _GTK_THEME_VARIANT property on windows when dark theme is in use, to make the window manager draw dark decorations.

You can verify it by comparing the signatures here with real signatures in xcb/xcb.h and xcb/xproto.h. You can also try to run any application with QT_STYLE_OVERRIDE=Adwaita-Dark on a 32-bit system, it should not crash.

Note that adwaita-qt should be compiled without ADWAITA_HAVE_X11. Actually I haven't figured out how to compile it with that flag, for example it needs qtx11extras but CMake does not add needed flags for that library.

[grulja]

I checked both header files, but I don't see these definitions.

[mitya57]

For me they are defined as follows:

/* In /usr/include/xcb/xcb.h */
xcb_connection_t *xcb_connect(const char *displayname, int *screenp);

/* In /usr/include/xcb/xproto.h */
xcb_intern_atom_cookie_t
xcb_intern_atom (xcb_connection_t *c,
                 uint8_t           only_if_exists,
                 uint16_t          name_len,
                 const char       *name);

xcb_intern_atom_reply_t *
xcb_intern_atom_reply (xcb_connection_t          *c,
                       xcb_intern_atom_cookie_t   cookie  /**< */,
                       xcb_generic_error_t      **e);

xcb_void_cookie_t
xcb_change_property (xcb_connection_t *c,
                     uint8_t           mode,
                     xcb_window_t      window,
                     xcb_atom_t        property,
                     xcb_atom_t        type,
                     uint8_t           format,
                     uint32_t          data_len,
                     const void       *data);

where the types are defined as:

/* In /usr/include/xcb/xcb.h */
typedef struct {
    unsigned int sequence;  /**< Sequence number */
} xcb_void_cookie_t;

/* In /usr/include/xcb/xproto.h */
typedef uint32_t xcb_window_t;
typedef uint32_t xcb_atom_t;

Note that any pointers may be safely replaced with void *, as that is the same from ABI / calling convention point of view.

[grulja]

You are correct, I wasn't searching them under correct name. Looks good to me now.