Re: Simple draw question
You should never draw anything in an enter/leave callback, but only in an expose event. Also note that creating/destroying a GC each time you draw it is very slow, so you should do something like this instead: Ok, I have questions here and they are because I really want to know why and not start anything. 1. Why is drawing in the enter in leave callback not something you should do? Is it because if you do to much it can cause a backlog of events? Merely a 'good design' question, but also because some prepare/release stuff is required before and after drawing on a GdkWindow (basicaly to set the clipping region and to setup the double buffer and copy its contents after the drawing operations). This is done by gdk_window_begin_paint_rect() and gdk_window_end_paint() which are automatically called by gtk when an expose event is processed. I think you can also call these yourself if you really want to keep your drawing within the leave/enter events, but a more 'conventional' way is to invalidate the window and then call gdk_window_process_updates() to process the expose event immediately. You'll find a lot of interesting things about that in the GdkWindow doc. 2. Actually while creating and destroying a GC may be slow (and I don't think it is actually that slow) it seems that in this case I should have just looked them up off the widget (which I didn't know there were several GCs off of the widget style). Not sure it is that slow, but using an existing one is obviously faster than creating it. It's also better (but of course not mandatory) to use the ones provided by the widget style, first because that's why they are here, and because it'll keep your app consistent if the user modify some style/resource settings (but I don't know much about that). For info, manys GCs are created by the style, see gtkstyle.h for a list of them. 3. I did try what you recommended and basically I found this. The expose event was not fired enough. I _think_ what happens is that GTK optimizes calls to event handlers and so if you send it 5 requests to expose on the same object and they stack up in the dispatcher, you only get one expose event called (this is actually the right thing to do) and so when I was testing this, I would get only one call to expose and so the box would never be drawn. (my guess could be totally wrong here). I don't understand what you mean here. It's true that gtk optimizes the invalidate calls, not by stacking them but by keeping an 'update_area' for each window and thus only redrawing the dirty part of it when nothing else has to be done (this is managed by an idle event). But even if you get only one call to expose, shouldn't it be enough to redraw it ? Finally, note that I'm definitely not a gtk wizard, so maybe am I only saying stupid things here ;) -- Cédric Lucantis ___ gtk-app-devel-list mailing list gtk-app-devel-list@gnome.org http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
Re: Simple draw question
Le samedi 5 mai 2007 00:48, Kevin DeKorte a écrit :
Hi,
I have a situation where I need to highlight an eventbox when a user
enters it and unhighlight it when the users leaves. I'm using this code
but the color I'm drawing in the leave_button_callback is always wrong
and varies from run to run with the program. Any ideas what I am doing
wrong. I was looking for a XOR option or something but I don't see it.
gboolean enter_button_callback (GtkWidget *widget, GdkEventCrossing
*event, gpointer data)
{
GdkGC *gc;
gc = gdk_gc_new(widget-window);
gdk_draw_rectangle(widget-window, gc, FALSE, 0, 0,
widget-allocation.width-1,
widget-allocation.height-1);
gdk_gc_unref(gc);
return FALSE;
}
gboolean leave_button_callback (GtkWidget *widget, GdkEventCrossing
*event, gpointer data)
{
GdkGC *gc;
GdkGCValues v;
GdkColor color;
GdkColormap *map;
gc = gdk_gc_new(widget-window);
map = gdk_gc_get_colormap(gc);
gdk_gc_get_values(gc,v);
gdk_colormap_query_color(map,v.background.pixel,color);
gdk_gc_set_foreground(gc,color);
gdk_draw_rectangle(widget-window, gc, FALSE, 0, 0,
widget-allocation.width-1,
widget-allocation.height-1);
gdk_gc_unref(gc);
return FALSE;
}
You should never draw anything in an enter/leave callback, but only in an
expose event. Also note that creating/destroying a GC each time you draw it
is very slow, so you should do something like this instead:
enter_button_callback()
{
gtk_widget_set_state(widget, GTK_STATE_PRELIGHT);
/* not sure this is required, as it's maybe called by set_state? */
/* you may use gdk_window_invalidate_* instead for better performances,
* see the docs for more infos */
gtk_widget_queue_draw(widget);
}
leave_button_callback()
{
/* same with GTK_STATE_NORMAL */
}
expose_button_callback()
{
gdk_draw_rectangle(widget-window, widget-state-fg_gc[widget-state],
...)
}
--
Cédric Lucantis
___
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Re: Simple draw question
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Hash: SHA1
Cédric Lucantis wrote:
Le samedi 5 mai 2007 00:48, Kevin DeKorte a écrit :
You should never draw anything in an enter/leave callback, but only in an
expose event. Also note that creating/destroying a GC each time you draw it
is very slow, so you should do something like this instead:
Ok, I have questions here and they are because I really want to know why
and not start anything.
1. Why is drawing in the enter in leave callback not something you
should do? Is it because if you do to much it can cause a backlog of
events?
2. Actually while creating and destroying a GC may be slow (and I don't
think it is actually that slow) it seems that in this case I should have
just looked them up off the widget (which I didn't know there were
several GCs off of the widget style).
3. I did try what you recommended and basically I found this. The expose
event was not fired enough. I _think_ what happens is that GTK optimizes
calls to event handlers and so if you send it 5 requests to expose on
the same object and they stack up in the dispatcher, you only get one
expose event called (this is actually the right thing to do) and so when
I was testing this, I would get only one call to expose and so the box
would never be drawn. (my guess could be totally wrong here).
enter_button_callback()
{
gtk_widget_set_state(widget, GTK_STATE_PRELIGHT);
/* not sure this is required, as it's maybe called by set_state? */
/* you may use gdk_window_invalidate_* instead for better performances,
* see the docs for more infos */
gtk_widget_queue_draw(widget);
}
leave_button_callback()
{
/* same with GTK_STATE_NORMAL */
}
expose_button_callback()
{
gdk_draw_rectangle(widget-window, widget-state-fg_gc[widget-state],
...)
}
Oh for others reading this the line should be
gdk_draw_rectangle(widget-window, widget-style-fg_gc[widget-state], ...)
Kevin
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Re: Simple draw question
I have been able, using GDK, to draw while entering and leaving. One
example could be in trying to create
a highlight effect as you enter a window.
Chris
Kevin DeKorte wrote:
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Hash: SHA1
Cédric Lucantis wrote:
Le samedi 5 mai 2007 00:48, Kevin DeKorte a écrit :
You should never draw anything in an enter/leave callback, but only in an
expose event. Also note that creating/destroying a GC each time you draw it
is very slow, so you should do something like this instead:
Ok, I have questions here and they are because I really want to know why
and not start anything.
1. Why is drawing in the enter in leave callback not something you
should do? Is it because if you do to much it can cause a backlog of
events?
2. Actually while creating and destroying a GC may be slow (and I don't
think it is actually that slow) it seems that in this case I should have
just looked them up off the widget (which I didn't know there were
several GCs off of the widget style).
3. I did try what you recommended and basically I found this. The expose
event was not fired enough. I _think_ what happens is that GTK optimizes
calls to event handlers and so if you send it 5 requests to expose on
the same object and they stack up in the dispatcher, you only get one
expose event called (this is actually the right thing to do) and so when
I was testing this, I would get only one call to expose and so the box
would never be drawn. (my guess could be totally wrong here).
enter_button_callback()
{
gtk_widget_set_state(widget, GTK_STATE_PRELIGHT);
/* not sure this is required, as it's maybe called by set_state? */
/* you may use gdk_window_invalidate_* instead for better performances,
* see the docs for more infos */
gtk_widget_queue_draw(widget);
}
leave_button_callback()
{
/* same with GTK_STATE_NORMAL */
}
expose_button_callback()
{
gdk_draw_rectangle(widget-window, widget-state-fg_gc[widget-state],
...)
}
Oh for others reading this the line should be
gdk_draw_rectangle(widget-window, widget-style-fg_gc[widget-state], ...)
Kevin
- --
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Simple draw question
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Hi,
I have a situation where I need to highlight an eventbox when a user
enters it and unhighlight it when the users leaves. I'm using this code
but the color I'm drawing in the leave_button_callback is always wrong
and varies from run to run with the program. Any ideas what I am doing
wrong. I was looking for a XOR option or something but I don't see it.
gboolean enter_button_callback (GtkWidget *widget, GdkEventCrossing
*event, gpointer data)
{
GdkGC *gc;
gc = gdk_gc_new(widget-window);
gdk_draw_rectangle(widget-window, gc, FALSE, 0, 0,
widget-allocation.width-1,
widget-allocation.height-1);
gdk_gc_unref(gc);
return FALSE;
}
gboolean leave_button_callback (GtkWidget *widget, GdkEventCrossing
*event, gpointer data)
{
GdkGC *gc;
GdkGCValues v;
GdkColor color;
GdkColormap *map;
gc = gdk_gc_new(widget-window);
map = gdk_gc_get_colormap(gc);
gdk_gc_get_values(gc,v);
gdk_colormap_query_color(map,v.background.pixel,color);
gdk_gc_set_foreground(gc,color);
gdk_draw_rectangle(widget-window, gc, FALSE, 0, 0,
widget-allocation.width-1,
widget-allocation.height-1);
gdk_gc_unref(gc);
return FALSE;
}
- --
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