Commit 8de17733 authored by Matthias Clasen's avatar Matthias Clasen
Browse files

Additions.

parent 2074c538
2003-06-30 Matthias Clasen <maclas@gmx.de>
* gtk/tmpl/gtkcontainer.sgml: Write a bit about size negotiation.
* gtk/tmpl/gtkwidget.sgml: Some additions.
2003-06-24 Matthias Clasen <maclas@gmx.de>
* gtk/gtk-docs.sgml: Move GtkIMContext to "Abstract Base Classes", since its abstract.
......
......@@ -5,7 +5,71 @@ GtkContainer
Base class for widgets which contain other widgets
<!-- ##### SECTION Long_Description ##### -->
<para id="child-properties">
<para>
A GTK+ user interface is constructed by nesting widgets inside widgets. Container widgets are the inner
nodes in the resulting tree of widgets: they contain other widgets. So, for example, you might have a
#GtkWindow containing a #GtkFrame containing a GtkLabel. If you wanted an image instead of a textual label
inside the frame, you might replace the #GtkLabel widget with a #GtkImage widget.
</para>
<para>
There are two major kinds of container widgets in GTK+. Both are subclasses of the abstract #GtkContainer
base class.
</para>
<para>
The first type of container widget has a single child widget and derives from #GtkBin. These containers
are <firstterm>decorators</firstterm>, which add some kind of functionality to the child. For example,
a #GtkButton makes its child into a clickable button; a #GtkFrame draws a frame around its child and
a #GtkWindow places its child widget inside a top-level window.
</para>
<para>
The second type of container can have more than one child; its purpose is to manage
<firstterm>layout</firstterm>. This means that these containers assign sizes and positions to their children.
For example, a #GtkHBox arranges its children in a horizontal row, and a #GtkTable arranges the widgets it
contains in a two-dimensional grid.
</para>
<para>
To fulfill its task, a layout container must negotiate the size requirements with its parent and its children.
This negotiation is carried out in two phases, <firstterm>size requisition</firstterm> and
<firstterm>size allocation</firstterm>.
</para>
<refsect2 id="size-requisition"><title>Size Requisition</title>
<para>
The size requisition of a widget is it's desired width and height. This is represented by a #GtkRequisition.
</para>
<para>
How a widget determines its desired size depends on the widget. A #GtkLabel, for example, requests enough space
to display all its text. Container widgets generally base their size request on the requisitions of their
children.
</para>
<para>
The size requisition phase of the widget layout process operates top-down. It starts at a top-level widget,
typically a #GtkWindow. The top-level widget asks its child for its size requisition by calling
gtk_widget_size_request(). To determine its requisition, the child asks its own children for their requisitions
and so on. Finally, the top-level widget will get a requisition back from its child.
</para>
</refsect2>
<refsect2 id="size-allocation"><title>Size Allocation</title>
<para>
When the top-level widget has determined how much space its child would like to have, the second phase of the
size negotiation, size allocation, begins. Depending on its configuration (see gtk_window_set_resizable()), the
top-level widget may be able to expand in order to satisfy the size request or it may have to ignore the size
request and keep its fixed size. It then tells its child widget how much space it gets by calling
gtk_widget_size_allocate(). The child widget divides the space among its children and tells each child how much
space it got, and so on. Under normal circumstances, a #GtkWindow will always give its child the amount of space
the child requested.
</para>
<para>
A child's size allocation is represented by a #GtkAllocation. This struct contains not only a width and height,
but also a position (i.e. X and Y coordinates), so that containers can tell their children not only how much
space they have gotten, but also where they are positioned inside the space available to the container.
</para>
<para>
Widgets are required to honor the size allocation they receive; a size request is only a request, and widgets
must be able to cope with any size.
</para>
</refsect2>
<refsect2 id="child-properties"><title>Child properties</title>
<para>
<structname>GtkContainer</structname> introduces <firstterm>child
properties</firstterm> - these are object properties that are not specific
to either the container or the contained widget, but rather to their relation.
......@@ -25,6 +89,7 @@ gtk_container_child_get_property(), gtk_container_child_get() or
gtk_container_child_get_valist(). To emit notification about child property
changes, use gtk_widget_child_notify().
</para>
</refsect2>
<!-- ##### SECTION See_Also ##### -->
<para>
......
......@@ -313,7 +313,7 @@ Evaluates to %TRUE if the #GTK_APP_PAINTABLE flag has been set on the widget.
Evaluates to %TRUE if the #GTK_DOUBLE_BUFFERED flag has been set on the widget.
</para>
@wid:
@wid: a #GtkWidget.
<!-- ##### MACRO GTK_WIDGET_SET_FLAGS ##### -->
......@@ -336,30 +336,34 @@ Turns off certain widget flags.
<!-- ##### USER_FUNCTION GtkCallback ##### -->
<para>
The type of the callback functions used for e.g. iterating over
the children of a container, see gtk_container_foreach().
</para>
@widget:
@data:
@widget: the widget to operate on
@data: user-supplied data
<!-- ##### STRUCT GtkRequisition ##### -->
<para>
A <structname>GtkRequisition</structname> represents the desired size of a widget. See
<xref linkend="size-requisition"/> for more information.
</para>
@width:
@height:
@width: the widget's desired width
@height: the widget's desired height
<!-- ##### STRUCT GtkAllocation ##### -->
<para>
A <structname>GtkAllocation</structname> of a widget represents region which has been allocated to the
widget by its parent. It is a subregion of its parents allocation. See
<xref linkend="size-allocation"/> for more information.
</para>
@x:
@y:
@width:
@height:
@x: the X position of the widgets area relative to its parents allocation.
@y: the Y position of the widgets area relative to its parents allocation.
@width: the width of the widgets allocated area.
@height: the height of the widgets allocated area.
<!-- ##### STRUCT GtkSelectionData ##### -->
<para>
......
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