Re: Question about mouse coordinates in GDK images

[tomas tuxteam de]

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On Sun, Dec 10, 2006 at 06:43:07PM -0800, Erik Walter wrote:
> I'm trying to do a fairly simple thing and I haven't been able to  
> find any answers (that work) to my problem.
>
> I just need to find the mouse (pointer) coordinates relative to a GDK  
> image's origin (i.e. the pixel that would be set via a  
> gdk_image_put_pixel() that corresponds to the pointer location).
>
> the GDK Image I have is in a GtkImage, inside a GtkScrolledWindow  
> (i.e. via gtk_scrolled_add_with_viewport()) and that's inside a  
> GtkEventBox and that's inside a GtkWindow.
>
> So basically....
>
> GDKImage
> GtkImage
> GtkScrolledWindow
> GtkEventBox
> GtkWindow
>
> Both gdk_window_get_pointer() and gtk_widget_get_pointer() always  
> return coordinates relative to the base window.  But if you resize  
> the window to be larger than the image, it centers it in the window  
> and the coordinates are wrong.
>
> The only way I can think to deal with this is REALLY hacky,   
> basically attempting to "predict" where the image is based on the  
> assumption that it's centered in the main window's dimensions and  
> doing some guesswork.  But that seems like the wrong way to approach  
> this.

Would this help (warning: untested):

  GtkImage *img;
  struct GtkAllocation alloc;
  gint imgx, imgy;
  ...
  imgx = GTK_WIDGET(img)->allocation.x;
  imgy = GTK_WIDGET(img)->allocation.y;
  
(or whatever equivalent code).

I would assume that the GtkImage's size matches the size of the
contained GdkImage (at least if you set its padding to zero).

Regards
- -- tomÃs
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