Make LdCanvas zoom on mouse wheel.
This commit is contained in:
		@@ -160,6 +160,7 @@ static void on_adjustment_value_changed
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	(GtkAdjustment *adjustment, LdCanvas *self);
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static void on_size_allocate (GtkWidget *widget, GtkAllocation *allocation,
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	gpointer user_data);
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static void update_adjustments (LdCanvas *self);
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static void diagram_connect_signals (LdCanvas *self);
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static void diagram_disconnect_signals (LdCanvas *self);
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@@ -175,6 +176,8 @@ static gboolean on_button_press (GtkWidget *widget, GdkEventButton *event,
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	gpointer user_data);
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static gboolean on_button_release (GtkWidget *widget, GdkEventButton *event,
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	gpointer user_data);
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static gboolean on_scroll (GtkWidget *widget, GdkEventScroll *event,
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	gpointer user_data);
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static void ld_canvas_color_set (LdCanvasColor *color,
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	gdouble r, gdouble g, gdouble b, gdouble a);
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@@ -310,6 +313,8 @@ ld_canvas_init (LdCanvas *self)
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		G_CALLBACK (on_button_press), NULL);
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	g_signal_connect (self, "button-release-event",
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		G_CALLBACK (on_button_release), NULL);
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	g_signal_connect (self, "scroll-event",
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		G_CALLBACK (on_scroll), NULL);
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	g_object_set (self, "can-focus", TRUE, NULL);
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@@ -474,10 +479,8 @@ on_size_allocate (GtkWidget *widget, GtkAllocation *allocation,
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	gpointer user_data)
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{
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	LdCanvas *self;
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	gdouble scale;
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	self = LD_CANVAS (widget);
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	scale = ld_canvas_get_scale_in_px (self);
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	/* FIXME: If the new allocation is bigger, we may see more than
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	 *        what we're supposed to be able to see -> adjust X and Y.
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@@ -485,17 +488,28 @@ on_size_allocate (GtkWidget *widget, GtkAllocation *allocation,
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	 *        If the visible area is just so large that we must see more,
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	 *        let's disable the scrollbars in question.
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	 */
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	update_adjustments (self);
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}
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static void
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update_adjustments (LdCanvas *self)
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{
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	gdouble scale;
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	scale = ld_canvas_get_scale_in_px (self);
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	if (self->priv->adjustment_h)
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	{
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		self->priv->adjustment_h->page_size = allocation->width / scale;
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		self->priv->adjustment_h->page_size
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			= GTK_WIDGET (self)->allocation.width  / scale;
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		self->priv->adjustment_h->value
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			= self->priv->x - self->priv->adjustment_h->page_size / 2;
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		gtk_adjustment_changed (self->priv->adjustment_h);
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	}
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	if (self->priv->adjustment_v)
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	{
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		self->priv->adjustment_v->page_size = allocation->height / scale;
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		self->priv->adjustment_v->page_size
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			= GTK_WIDGET (self)->allocation.height / scale;
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		self->priv->adjustment_v->value
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			= self->priv->y - self->priv->adjustment_v->page_size / 2;
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		gtk_adjustment_changed (self->priv->adjustment_v);
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@@ -1006,6 +1020,29 @@ on_button_release (GtkWidget *widget, GdkEventButton *event, gpointer user_data)
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	return FALSE;
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}
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static gboolean
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on_scroll (GtkWidget *widget, GdkEventScroll *event, gpointer user_data)
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{
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	LdCanvas *self;
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	self = LD_CANVAS (widget);
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	switch (event->direction)
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	{
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	case GDK_SCROLL_UP:
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		self->priv->zoom *= 1.5;
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		break;
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	case GDK_SCROLL_DOWN:
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		self->priv->zoom /= 1.5;
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		break;
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	default:
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		return FALSE;
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	}
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	update_adjustments (self);
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	gtk_widget_queue_draw (widget);
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	return TRUE;
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}
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static gboolean
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on_expose_event (GtkWidget *widget, GdkEventExpose *event, gpointer user_data)
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{
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