Re: [cairo-compmgr] Re: magnifier plugin prove of concept

[gandalfn <gandalfn@xxxxxxxxxxxxxxxx>]

hi, carlos

Very good job, you are in the right way.

Only some points : first instead create a window (which is redirected by
compositing), use cairo surface that you can create from root window
surface or cow surface in screen paint implementation like this:

if (!self->priv->surface)
{
  CCMWindow* root = ccm_screen_get_root_window(screen);
  cairo_surface_t* surface =     
                      ccm_drawable_get_surface(CCM_DRAWABLE(root));

  self->priv->surface = cairo_surface_create_similar(surface, w , h);
  cairo_surface_destroy(surface);
}

After in window paint implementation create a context from this surface
and paint window on it, like you do, but don't forget the magnifier
offset in screen:
....
cairo_t* ctx = cairo_create(self->priv->surface);

// Translate to -x,-y offset of magnifier to have same coords of screen
cairo_translate(ctx, -x_offset, -y_offset);
// Magnifier scale
cairo_scale(ctx, scale_x, scale_y);
// Set clip zone to size of magnifier to don't draw outsite the
magnifier surface
cairo_rectangle(ctx, 0, 0, width, height);
cairo_clip(ctx);
// Paint the window
ret = ccm_window_plugin_paint (CCM_WINDOW_PLUGIN_PARENT(plugin), window,
			       ctx, surface);
....

You can also in this point, test if window is visible in magnifier with
ccm_region_rect_in to don't draw it when is outside magnifier.

To finish, i think we need a new function in screen which get cow
context like this :

cairo_t* 
ccm_screen_get_context(CCMScreen* self)
{
  if (!self->priv->ctx)
  {
     self->priv->ctx =             
             ccm_drawable_create_context(CCM_DRAWABLE(self->priv->cow));
  }
  return self->priv->ctx;
}

or add this context at parameters of ccm_screen_plugin_paint.

and after in end of screen paint, we can paint the magnifier like this:

cairo_t* context = ccm_screen_get_context(screen);
cairo_set_source_surface(context, self->priv->surface, x_pos, y_pos);
cairo_paint(context);

I write this code very quickly, and it can contains some mistakes ;)

Nicolas
-- 
gandalfn <gandalfn@xxxxxxxxxxxxxxxx>

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