所以我正在开发我的第一个gdk_pixbuf_module。向webp模块添加动画。尽管在头文件和c文件中尝试了许多变体，但我仍然会收到这些链接错误，我认为这些错误与gdk_pixbuf宏有关。我猜我做错了一件简单的事，但我无法发现。我们很感激你的帮助。
这是io-webp-anim.h:的头文件
//
// Created by alan on 2021-07-15.
//
#ifndef IO_WEBP_ANIM_H
#define IO_WEBP_ANIM_H
//#include <glib-object.h>
#include <webp/types.h>
#include <webp/decode.h>
#include <webp/encode.h>
#include <webp/mux_types.h>
//#include <webp/mux.h>
#include <webp/demux.h>
#include <string.h>
#define GDK_PIXBUF_ENABLE_BACKEND
//#include <gdk-pixbuf/gdk-pixbuf.h>
#include <gdk-pixbuf/gdk-pixbuf-io.h>
#include <gdk-pixbuf/gdk-pixbuf-animation.h>
#undef GDK_PIXBUF_ENABLE_BACKEND
typedef struct MyWebPData MyWebPData;
typedef struct _GdkPixbufWebpAnim GdkPixbufWebpAnim;
typedef struct _GdkPixbufWebpAnimClass GdkPixbufWebpAnimClass;
#define GDK_TYPE_PIXBUF_WEBP_ANIM (gdk_pixbuf_webp_anim_get_type ())
#define GDK_PIXBUF_WEBP_ANIM(object) (G_TYPE_CHECK_INSTANCE_CAST ((object), GDK_TYPE_PIXBUF_WEBP_ANIM, GdkPixbufWebpAnim))
#define GDK_IS_PIXBUF_WEBP_ANIM(object) (G_TYPE_CHECK_INSTANCE_TYPE ((object), GDK_TYPE_PIXBUF_WEBP_ANIM))
#define GDK_PIXBUF_WEBP_ANIM_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST ((klass), GDK_TYPE_PIXBUF_WEBP_ANIM, GdkPixbufWebpAnimClass))
#define GDK_IS_PIXBUF_WEBP_ANIM_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), GDK_TYPE_PIXBUF_WEBP_ANIM))
#define GDK_PIXBUF_WEBP_ANIM_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), GDK_TYPE_PIXBUF_WEBP_ANIM, GdkPixbufWebpAnimClass))
typedef struct _WebPContext WebPContext;
typedef struct _GdkPixbufWebpAnimIter GdkPixbufWebpAnimIter;
struct _GdkPixbufWebpAnim {
GdkPixbufAnimation parent_instance;
WebPContext *context;
WebPAnimInfo *animInfo;
WebPAnimDecoderOptions *decOptions;
WebPAnimDecoder *dec; // dec and demuxer have identical lifetimes.
const WebPDemuxer *demuxer;
GdkPixbufWebpAnimIter *webp_iter;
};
struct _GdkPixbufWebpAnimClass {
GdkPixbufAnimationClass parent_class;
//GObject parent_class;
};
GType gdk_pixbuf_webp_anim_get_type (void) G_GNUC_CONST;
// GdkPixbufWebpAnimIter -->
typedef struct _GdkPixbufWebpAnimIterClass GdkPixbufWebpAnimIterClass;
#define GDK_TYPE_PIXBUF_WEBP_ANIM_ITER (gdk_pixbuf_webp_anim_iter_get_type ())
#define GDK_PIXBUF_WEBP_ANIM_ITER(object) (G_TYPE_CHECK_INSTANCE_CAST ((object), GDK_TYPE_PIXBUF_WEBP_ANIM_ITER, GdkPixbufWebpAnimIter))
#define GDK_IS_PIXBUF_WEBP_ANIM_ITER(object) (G_TYPE_CHECK_INSTANCE_TYPE ((object), GDK_TYPE_PIXBUF_WEBP_ANIM_ITER))
#define GDK_PIXBUF_GIF_ANIM_ITER_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST ((klass), GDK_TYPE_PIXBUF_GIF_ANIM_ITER, GdkPixbufGifAnimIterClass))
#define GDK_IS_PIXBUF_GIF_ANIM_ITER_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), GDK_TYPE_PIXBUF_GIF_ANIM_ITER))
#define GDK_PIXBUF_GIF_ANIM_ITER_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), GDK_TYPE_PIXBUF_GIF_ANIM_ITER, GdkPixbufGifAnimIterClass))
G_GNUC_BEGIN_IGNORE_DEPRECATIONS
struct _GdkPixbufWebpAnimIter { /* FIXME - struct is actually gif type */
GdkPixbufAnimationIter parent_instance;
GdkPixbufWebpAnim *webp_anim;
WebPIterator *iter;
//WebPData *data;
GTimeVal start_time;
GTimeVal current_time;
GTimeVal frame_start_time;
long position; // Time in milliseconds into this run of the animation
long cur_frame_start; // start time in millisec.
gint cur_duration;
int cur_frame;
gint first_loop_slowness;
};
G_GNUC_END_IGNORE_DEPRECATIONS
struct _GdkPixbufWebpAnimIterClass {
GdkPixbufAnimationIterClass parent_class;
//GObject parent_class;
};
GType gdk_pixbuf_webp_anim_iter_get_type (void) G_GNUC_CONST;
#endif //IO_WEBP_ANIM_H
以下是io-webp anim.c文件的摘录：
#include "io-webp-anim.h"
// ... fcn def's.
static void gdk_pixbuf_webp_anim_get_size (GdkPixbufAnimation *animation,
int *width,
int *height) {
GdkPixbufWebpAnim *anim = GDK_PIXBUF_WEBP_ANIM (animation);
if (anim && anim->context) {
*width = anim->context->features.width;
*height = anim->context->features.height;
}
}
// more fcn def's.
static int gdk_pixbuf_webp_anim_iter_get_delay_time (GdkPixbufAnimationIter *iter) {
GdkPixbufWebpAnimIter *webp_iter;
webp_iter = GDK_PIXBUF_WEBP_ANIM_ITER (iter);
int dur = -1;
if (webp_iter && webp_iter->iter) {
dur = webp_iter->iter->duration;
}
return dur;
}
两个宏GDK_PIXBUF_WEBP_ANIM和GDK_PIXBUF_WEB_p_ANIM_ITER执行类型转换，涉及fcns:GDK_PIXBUF_web_ANIM_get_type和GDK_pix buf-web_ANIM_ITER_get_type。现在，在我发现的gdk_pixbuf模块的例子中，我没有必要实现这些函数——它们似乎可以通过宏自动神奇地处理。
然而，我的构建给出了错误(好像我需要专门定义那些fcn(：
ninja -C builddir
ninja: Entering directory `builddir'
[1/7] Compiling C object 'tests/59830eb@@t2@exe/t2.c.o'.
[2/7] Compiling C object 'tests/59830eb@@t1@exe/t1.c.o'.
../tests/t1.c: In function ‘main’:
../tests/t1.c:34:13: warning: unused variable ‘asdf’ [-Wunused-variable]
int asdf = 1;
^~~~
../tests/t1.c:33:20: warning: unused variable ‘image’ [-Wunused-variable]
GdkPixbuf *image = gdk_pixbuf_animation_get_static_image (anim);
^~~~~
../tests/t1.c:42:13: warning: unused variable ‘delay’ [-Wunused-variable]
int delay = gdk_pixbuf_animation_iter_get_delay_time(anim_iter);
^~~~~
[3/7] Compiling C object 'pixbufloader-webp@sha/io-webp-anim.c.o'.
../io-webp-anim.c:697:1: warning: ‘gdk_pixbuf_webp_anim_iter_class_init’ defined but not used [-Wunused-function]
gdk_pixbuf_webp_anim_iter_class_init (GdkPixbufWebpAnimIterClass *klass)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../io-webp-anim.c:589:1: warning: ‘gdk_pixbuf_webp_anim_iter_init’ defined but not used [-Wunused-function]
gdk_pixbuf_webp_anim_iter_init (GdkPixbufWebpAnimIter *iter)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../io-webp-anim.c:581:1: warning: ‘gdk_pixbuf_webp_anim_init’ defined but not used [-Wunused-function]
gdk_pixbuf_webp_anim_init (GdkPixbufWebpAnim *anim)
^~~~~~~~~~~~~~~~~~~~~~~~~
../io-webp-anim.c:567:1: warning: ‘gdk_pixbuf_webp_anim_class_init’ defined but not used [-Wunused-function]
gdk_pixbuf_webp_anim_class_init (GdkPixbufWebpAnimClass *klass)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[4/7] Linking target libpixbufloader-webp.so.
FAILED: libpixbufloader-webp.so
cc -o libpixbufloader-webp.so 'pixbufloader-webp@sha/io-webp-anim.c.o' -Wl,--as-needed -Wl,--no-undefined -shared -fPIC -Wl,--start-group -Wl,-soname,libpixbufloader-webp.so -lgtk-3 -lgdk-3 -lpangocairo-1.0 -lpango-1.0 -latk-1.0 -lcairo-gobject -lcairo -lgdk_pixbuf-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 /usr/lib/x86_64-linux-gnu/libgdk_pixbuf-2.0.so /usr/lib/x86_64-linux-gnu/libgobject-2.0.so /usr/lib/x86_64-linux-gnu/libglib-2.0.so /usr/lib/x86_64-linux-gnu/libwebp.so /usr/lib/x86_64-linux-gnu/libwebpdemux.so -Wl,--end-group
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_image_is_static_image':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:450: undefined reference to `gdk_pixbuf_webp_anim_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_get_static_image':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:470: undefined reference to `gdk_pixbuf_webp_anim_get_type'
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:473: undefined reference to `gdk_pixbuf_webp_anim_iter_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_get_iter':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:502: undefined reference to `gdk_pixbuf_webp_anim_iter_get_type'
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:503: undefined reference to `gdk_pixbuf_webp_anim_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_get_size':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:518: undefined reference to `gdk_pixbuf_webp_anim_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_iter_get_pixbuf':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:533: undefined reference to `gdk_pixbuf_webp_anim_iter_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_iter_get_delay_time':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:601: undefined reference to `gdk_pixbuf_webp_anim_iter_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_iter_on_currently_loading_frame':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:612: undefined reference to `gdk_pixbuf_webp_anim_iter_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf_webp_anim_iter_advance':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:626: undefined reference to `gdk_pixbuf_webp_anim_iter_get_type'
pixbufloader-webp@sha/io-webp-anim.c.o: In function `gdk_pixbuf__webp_image_load_animation':
/home/alan/projects/webp/aghtest/webp-pixbuf-loader/builddir/../io-webp-anim.c:781: undefined reference to `gdk_pixbuf_webp_anim_get_type'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.
Process finished with exit code 1
这是怎么回事？
找到了答案。以下宏必须添加到.c文件顶部附近：
G_DEFINE_TYPE (GdkPixbufWebpAnim, gdk_pixbuf_webp_anim, GDK_TYPE_PIXBUF_ANIMATION)
G_DEFINE_TYPE (GdkPixbufWebpAnimIter, gdk_pixbuf_webp_anim_iter, GDK_TYPE_PIXBUF_ANIMATION_ITER)