c++ - Qt 4.7 - glTexSubImage2D returns GL_INVALID_OPERATION -

i'm using qglwidget draw own picture via opengl in qt 4.7.2. use opengl because want stretch image fast , less cpu usage.

for have 3 methods. 1 initialize opengl environment, 1 update image data different thread , 1 draw image itself.

the problem in updateimage method call of gltexsubimage2d() return gl_invalid_operation error. tried debug gdebugger 1 error. if context 1 of program see texture size 0x0, after call of gltexsubimage2d();

init opengl

void class::openglinit(void){    qglcontext* context = const_cast<qglcontext *>(qglcontext::currentcontext());    if (!context)    {     qdebug() << "can not current opengl context";     return;    }    context->makecurrent();    glgentextures(1,&texture);    glbindtexture(gl_texture_2d, texture);    glpixelstorei(gl_unpack_alignment, 1);    gltexparameteri(gl_texture_2d, gl_texture_min_filter, gl_linear);    gltexparameteri(gl_texture_2d, gl_texture_mag_filter, gl_linear);    gltexparameteri(gl_texture_2d, gl_texture_wrap_s, gl_clamp_to_edge);    gltexparameteri(gl_texture_2d, gl_texture_wrap_t, gl_clamp_to_edge);    gltexparameteri(gl_texture_2d,gl_texture_base_level,0);    gltexparameteri(gl_texture_2d,gl_texture_max_level,0);    glteximage2d(gl_texture_2d, 0, gl_rgba, 1024, 1024, 0, gl_rgba, gl_unsigned_int_8_8_8_8, null);    glbindtexture(gl_texture_2d,0); } 

update image

void class::updateimage(void){    datapointer = (u_int8_t*) malloc(1024*1024*4);    memcpy(datapointer,externalbuffer,1024*1024*4);     glbindtexture(gl_texture_2d, texture);    gltexsubimage2d(gl_texture_2d,0, 0,0,1024,1024,gl_rgba,gl_unsigned_int_8_8_8_8,datapointer);    //this line returns gl_invalid_operation  } 

draw image

void class::paintevent(qpaintevent *event){     qpainter painter(this);     painter.beginnativepainting();     glclearcolor(0.0f,0.0f,0.0f,0.0f);     glclear(gl_color_buffer_bit|gl_depth_buffer_bit);     //draw black screen     glenable(gl_texture_2d);     glbindtexture(gl_texture_2d, texture);     glbegin(gl_quads);         //draw picture         gltexcoord2f(0, 0);         glvertex2f(0, 0);         gltexcoord2f(1024, 0);         glvertex2f(1024, 0);         gltexcoord2f(1024, 1024);         glvertex2f(1024,1024);         gltexcoord2f(0, 1024);         glvertex2f(0, 1024);  glend(); gldisable(gl_texture_2d); painter.endnativepainting(); } 

i notice mentioned "update image thread", right? error might due missing ogl context in thread call 'updateimage'. please try call in same thread ogl context init , make current.