Skia as a static library in android app: undefined references related to OpenGL

[Athos Bacchiocchi]

hi, I'm again trying to use Skia as a static library in my android app.
I checked out revision 8363, successfully build static libraries using:

android_make -d arm -j2 BUILDTYPE=Release

Then I package the static libs located in
/trunk/out/config/android-arm/Release, using "merge_static_libs.py"
found in trunk/tools.

In particular I'm adding:
libskia_core.a
libskia_ports.a
libskia_opts.a
libskia_images.a
libskia_effects.a
libskia_utils.a
libskia_skgr.a
libskia_gr.a
libskia_xml.a
libfreetype.a
obj.target/gyp/libexpat.a

Then I add the library (libskia_custom.a) to my android.mk file, as a
prebuilt module, like this:

SKIA_FLAGS := -DSK_BUILD_FOR_ANDROID -DSK_BUILD_FOR_ANDROID_NDK \
-DSK_ALLOW_STATIC_GLOBAL_INITIALIZERS=0 \
-DSK_SCALAR_IS_FLOAT -DSK_CAN_USE_FLOAT \
-DSK_USE_POSIX_THREADS \
-DSK_GAMMA_SRGB -DSK_GAMMA_APPLY_TO_A8\
-DSK_SUPPORT_GPU=1 -DGR_ANDROID_BUILD=1 \
-DSK_RELEASE -DGR_RELEASE=1 -DNDEBUG

SKIA_INCLUDES := $(SKIA_DIR)/include/gpu $(SKIA_DIR)/include/core \
$(SKIA_DIR)/include/effects
$(SKIA_DIR)/include/utils \
$(SKIA_DIR)/include/pipe
$(SKIA_DIR)/include/config \
$(SKIA_DIR)/include/images
$(SKIA_DIR)/include/lazy

include $(CLEAR_VARS)
LOCAL_PATH := $(SKIA_LOCAL_PATH)
LOCAL_MODULE := skiacustom_static
LOCAL_SRC_FILES := libskia_custom.a
LOCAL_LDLIBS := -lGLESv2 -lEGL
LOCAL_EXPORT_CFLAGS := $(SKIA_FLAGS)
LOCAL_EXPORT_C_INCLUDES := $(SKIA_INCLUDES)
include $(PREBUILT_STATIC_LIBRARY)

And then I list it as a dependency in my native module:

LOCAL_LDLIBS := -llog -lGLESv2 -lEGL -lOpenSLES -lm -landroid
LOCAL_STATIC_LIBRARIES += skiacustom_static

But I'm getting some undefined references, listed here:

/Users/athos/Documents/android-ndk-r8d/toolchains/arm-linux-androideabi-4.6/prebuilt/darwin-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld:
./obj/local/armeabi/libskia_custom.a(GrGLCreateNativeInterface_android.o):
in function
GrGLCreateNativeInterface():GrGLCreateNativeInterface_android.cpp(.text+0x640):
error: undefined reference to 'glBindVertexArrayOES'
/Users/athos/Documents/android-ndk-r8d/toolchains/arm-linux-androideabi-4.6/prebuilt/darwin-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld:
./obj/local/armeabi/libskia_custom.a(GrGLCreateNativeInterface_android.o):
in function
GrGLCreateNativeInterface():GrGLCreateNativeInterface_android.cpp(.text+0x688):
error: undefined reference to 'glDeleteVertexArraysOES'
/Users/athos/Documents/android-ndk-r8d/toolchains/arm-linux-androideabi-4.6/prebuilt/darwin-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld:
./obj/local/armeabi/libskia_custom.a(GrGLCreateNativeInterface_android.o):
in function
GrGLCreateNativeInterface():GrGLCreateNativeInterface_android.cpp(.text+0x6bc):
error: undefined reference to 'glGenVertexArraysOES'
/Users/athos/Documents/android-ndk-r8d/toolchains/arm-linux-androideabi-4.6/prebuilt/darwin-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld:
./obj/local/armeabi/libskia_custom.a(GrGLCreateNativeInterface_android.o):
in function
GrGLCreateNativeInterface():GrGLCreateNativeInterface_android.cpp(.text+0x7a0):
error: undefined reference to 'glFramebufferTexture2DMultisampleIMG'
/Users/athos/Documents/android-ndk-r8d/toolchains/arm-linux-androideabi-4.6/prebuilt/darwin-x86/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld:
./obj/local/armeabi/libskia_custom.a(GrGLCreateNativeInterface_android.o):
in function
GrGLCreateNativeInterface():GrGLCreateNativeInterface_android.cpp(.text+0x7a4):
error: undefined reference to 'glRenderbufferStorageMultisampleIMG'

I believe these are related to OpenGL, as they are declared in gl2ext.h,
but since I included -lGLESv2 I thought I would be "covered". Did this
happen to anyone? Do you have any suggestion?

Thanks,
athos

[petra Z]

Hi,

I encountered the same problem as you. Do you have a method to solve the problem?

Please help me ,thanks a lot. 

在 2013年3月27日星期三UTC+8上午12时07分45秒，athos bacchiocchi写道：

[Athos Bacchiocchi]

I didn't solve yet, and due to the lack of time to explore the issue, I ended up using the the shared library compiled together with the sample app, specifically "libbench.so". It contains everything, surely also many useless stuff, but at least it works.

I guess that the functions causing the errors are not implemented in android's opengl, so one should find a way not to call them when compiling skia for android. I might be wrong, but it seems that all of them are inside an #ifdef that could help excluding them, but I don't remember which one, in this moment.

athos



Il 29/03/13 02.41, petra Z ha scritto:

[Janez Zemva]

Not necessarily unimplemented, you simply need to find them with egl and declare your own functions implementing them. They might be implemented, or not, depending on the graphics chip.

Example:

static PFNGLBINDVERTEXARRAYOESPROC pFNGLBINDVERTEXARRAYOESPROC;

static PFNGLDELETEVERTEXARRAYSOESPROC pFNGLDELETEVERTEXARRAYSOESPROC;

static PFNGLGENVERTEXARRAYSOESPROC pFNGLGENVERTEXARRAYSOESPROC;

static PFNGLISVERTEXARRAYOESPROC pFNGLISVERTEXARRAYOESPROC;

void glBindVertexArrayOES(GLuint array)

{

  (*pFNGLBINDVERTEXARRAYOESPROC)(array);

}

void glDeleteVertexArraysOES(GLsizei n, const GLuint *arrays)

{

  (*pFNGLDELETEVERTEXARRAYSOESPROC)(n, arrays);

}

void glGenVertexArraysOES(GLsizei n, GLuint *arrays)

{

  (*pFNGLGENVERTEXARRAYSOESPROC)(n, arrays);

}

GLboolean glIsVertexArrayOES(GLuint array)

{

  return (*pFNGLISVERTEXARRAYOESPROC)(array);

}

Here you "implement" the missing functions via some functions. Android leaves this up to you. If you fiddle in C/C++ you need to also know details like these.

2013/3/29 Athos Bacchiocchi <at...@ntrack.com>

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[petra Z]

Hi,

    I wrote a very simple sample, used the same method with your. Link is ok, but when I executed the program, "canvas.drawLine( 0, 0, 100, 100, paint ); "was crash.

    can you help me?

    thanks a lot.

   

    SkGraphics::Init();

LOGI( "before draw line"  );

SkPaint paint;

paint.setARGB( 255, 0, 0, 0 );

LOGI( "create bitmap"  );

SkBitmap bitmap;

bitmap.setConfig( SkBitmap::kARGB_8888_Config, 400, 400 );

bitmap.allocPixels();

LOGI( "create canvas"  );

SkCanvas canvas( bitmap );

canvas.drawLine( 0, 0, 300, 300, paint );

在 2013年3月29日星期五UTC+8下午10时48分39秒，athos bacchiocchi写道：

[Janez Zemva]

If you mean the code sample I've sent. Of course it crashed: I didn't initialize the function pointers in it - that was an exercise left over to you. Check this site on how to proceed further:

https://bitbucket.org/alfonse/glloadgen/wiki/Home

2013/4/1 petra Z <petr...@gmail.com>

--