changing codes implemeted with cairo_t to Cairo::RefPtr<Cairo::Context> - gtk

Question

i have some codes which i need to reimplement with Cairo::RefPtrCairo::Context...It is a bit confusing since i could not find good example which uses pattern while we have Cairo::RefPtrCairo::Context instead of cairo_t..
Cairo::RefPtr<Cairo::Surface> surface =
Cairo::ImageSurface::create(Cairo::FORMAT_ARGB32, width, height);
Cairo::RefPtr<Cairo::Context> cr = Cairo::Context::create(surface);
cairo_pattern_t *cp = cairo_pattern_create_radial(x_off, y_off, 0, x_off, y_off, cent_point_radius);
cairo_pattern_add_color_stop_rgba(cp, 0.0, 0.7, 0.7, 0.7, 0.8);
cairo_pattern_add_color_stop_rgba(cp, 1.0, 0.1, 0.1, 0.1, 0.8);
cairo_set_source(cr, cp);
How i can change "cp" to something which is recognizable for cr->set_resource().....cr used to be a cairo_t,but then i had to change it to Cairo::RefPtrCairo::Context
best regards

Answer 1

Since you've already decided to do it the C++ way, why not go all the way in?
// Create image surface.
Cairo::RefPtr <Cairo::Surface> refSurface =
Cairo::ImageSurface::create(Cairo::FORMAT_ARGB32,
nWidth,
nHeight);
// Create Cairo context for the image surface.
Cairo::RefPtr <Cairo::Context> refContext =
Cairo::Context::create(refSurface);
// Create a radial gradient (pattern)
Cairo::RefPtr <Cairo::RadialGradient> refPattern =
Cairo::RadialGradient::create(x_off,
y_off,
0,
x_off,
y_off,
cent_point_radius);
// Add color stops to the pattern
refPattern->add_color_stop_rgba(0.0,
0.7,
0.7,
0.7,
0.8);
refPattern->add_color_stop_rgba(1.0,
0.1,
0.1,
0.1,
0.8);
// Set the pattern as the source for the context.
refContext->set_source(refPattern);
// Add a closed path and fill...