Re: gtk_widget_set_size_request stopped working with GTK3

[Andrew Potter <agpotter gmail com>]

When creating a new widget subclass, you end up implementing
get_preferred_height/width. This allows you to specify both a
"minimum" and a "natural" size. Then in on_size_allocate() you can
decide to maybe set a clipped or scaled version of your pixbuf to a
GtkImage. When you do it this way, you don't need to put the image in
a scrolled window either.

Its a shame there are only methods to expose the minimum width and not
also the natural width on the default widgets, but I'd guess its
difficult to abstract across all widgets. But it does seem like
GtkImage should at least expose the natural width, as it seems like a
common problem one would have with pictures.

On Fri, Sep 28, 2012 at 11:28 PM, Tristan Van Berkom <tvb gnome org> wrote:
> Lets not go around the merry-go-round one more time.
>
> In GTK+3, widgets receive *at least* what they requested in the size
> requesting phase.
>
> User facing apis cannot undermine the minimal requirements for the geometry
> which a widget has requested.
>
> User facing apis can however, enforce a minimum size (i.e. the widget
> will be at least "this big")
> or they can configure a widget in such a way that it will require less size.
>
> The "pixel-size" thing not working for pixbufs could be considered an
> enhancement
> request bug for GtkImage.
>
> i.e. it should support clipping of pixbufs (and then, it should also
> need some alignment
> parameters to decide which portion of the input image should be
> clipped, also pixel-size
> does not really imply clipping directly, the user might very well
> expect the image to scale
> to the desired size).
>
> On Sat, Sep 29, 2012 at 2:28 AM, Steffen Gutmann <muibase yahoo com> wrote:
> [...]
>> Here is what I am trying to do.
>>
>> I have an image.  The center part of the image contains a logo that I want to display to the user.  Around the center part there is little extra content that is not important but nice to have.  With GTK2 I set the min size (properties "with-request" and "height-request") to just about the size of the logo, place the GtkImage into a GtkWindow, set the default size of the GtkWindow to slightly larger than the min size but smaller than the fulll size of the image, make the window resizable, and show it to the user.  GtkImage in GTK2 automatically clipped the image and centered it.  The user can enlarge the window and see more of the image, or shrink it down to the min size where only the logo stays visible.
>>
>> I have not found a way yet to achive the same with GTK3.
>
> a.) Create a GtkDrawingArea
>
> b.) Connect to "draw" signal
>
> c.) Use this code:
>
>    gdk_cairo_set_source_pixbuf (cr, pixbuf, x, y);
>    cairo_paint (cr);
>    (borrowed directly from:
> http://developer.gnome.org/gtk3/3.5/gtk-migrating-2-to-3.html)
>
>
> The above should pretty much get you what you want, just consider the widget's
> allocation at "draw" time and use that to offset the given x,y for
> gdk_cairo_set_source_pixbuf().
>
> Cheers,
>              -Tristan
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