Re: gtk_widget_set_size_request delayed until next allocation change

[jjacky <i am jack mail gmail com>]

On 04/27/13 02:35, Sandro Mani wrote:
> Hello,
>
> I have a GtkDrawingArea inside a GtkViewport, and I have a callback
> connected to the "size-allocate" signal of the GtkViewport which resizes
> the GtkDrawingArea by calling gtk_widget_set_size_request on the latter,
> see sample source code below.
>
> I however notice that the GtkDrawingArea allocates the requested size
> only the _next_ time the allocation of the GtkViewport changes, and
> hence the allocation of the GtkDrawingArea is the one requested for the
> previous allocation of the GtkViewport.
>
> The issue is best visible when maximizing and unmaximizing the window:
> when maximizing, the size of the GtkDrawingArea is still the one for the
> unmaximized state, and when unmaximizing again, the size of the
> GtkDrawingArea is the one for the maximized state.
>
> Question: Is this a mistake in my code or a Gtk bug? I'm using
> gtk3-3.8.1-1.fc20.x86_64

Seems you could fix it by setting GTK_RESIZE_IMMEDIATE as resize mode on
the viewport, although it seems to be deprecated.

I'm not sure what's the proper/recommended way to go it instead, but
instead of calling gtk_widget_queue_resize() and the
gtk_main_iteration() loop in resize_drawarea() you could call
gtk_container_resize_children() (on the viewport).
Although, since it triggers a new size-allocate, it might be a good idea
to block your handler to avoid it getting triggered again.

-j

> Thanks for any inputs.
>
> Sandro
>
> ------ Sample code: ------
> // gcc alloc.c -o alloc $(pkg-config --cflags --libs gtk+-3.0)
> #include <gtk/gtk.h>
> #include <stdio.h>
>
> void resize_drawarea (GtkWidget* viewport, GdkRectangle* rect, gpointer
> data)
> {
>   gtk_widget_set_size_request (GTK_WIDGET (data), rect->width / 2,
> rect->height / 2);
>   gtk_widget_queue_resize (GTK_WIDGET (data));
>   printf("set_size_request(%d, %d)\n", rect->width /2, rect->height / 2);
>   // Wait for size_request
>   while (gtk_events_pending ()) {
>     gtk_main_iteration ();
>   }
>   int w = gtk_widget_get_allocated_width (GTK_WIDGET (data));
>   int h = gtk_widget_get_allocated_height (GTK_WIDGET (data));
>   printf("allocation = %d x %d\n\n", w, h);
> }
>
> int main(int argc, char* argv[])
> {
>   gtk_init (&argc, &argv);
>   GtkWidget* window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
>   GtkWidget* viewport = gtk_viewport_new (NULL, NULL);
>   GtkWidget* drawarea = gtk_drawing_area_new ();
>
>   gtk_container_add (GTK_CONTAINER (window), viewport);
>   gtk_container_add (GTK_CONTAINER (viewport), drawarea);
>
>   gtk_widget_set_halign (drawarea, GTK_ALIGN_CENTER);
>   gtk_widget_set_valign (drawarea, GTK_ALIGN_CENTER);
>   GdkRGBA black = {0., 0., 0., 1.};
>   gtk_widget_override_background_color (drawarea, GTK_STATE_FLAG_NORMAL,
> &black);
>   gtk_window_set_default_size (GTK_WINDOW (window), 640, 480);
>
>   g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);
>   g_signal_connect (viewport, "size-allocate", G_CALLBACK
> (resize_drawarea), drawarea);
>
>   gtk_widget_show_all (window);
>   gtk_main ();
>   return 0;
> }
>
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