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docs: Some cosmetic fixups

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Some leftover comments from the drawing model rewrite.
This commit is contained in:
Matthias Clasen 2019-02-24 10:37:33 -05:00
parent edc4f954c6
commit 8a0182e401
1 changed files with 10 additions and 12 deletions
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22
docs/reference/gtk/drawing-model.xml
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@ -45,7 +45,7 @@
windows gets raised to the top, then the application has to windows gets raised to the top, then the application has to
repaint it, so the previously obscured area can be shown. repaint it, so the previously obscured area can be shown.
When the windowing system asks an application to redraw When the windowing system asks an application to redraw
a window, it sends an <firstterm>frame event</firstterm> a window, it sends a <firstterm>frame event</firstterm>
(<firstterm>expose event</firstterm> in X11 terminology) (<firstterm>expose event</firstterm> in X11 terminology)
for that window. for that window.
</para> </para>
@ -64,16 +64,14 @@
tell the underlying surface that it needs to repaint itself. The tell the underlying surface that it needs to repaint itself. The
drawing cycle can also be initiated when a widget itself decides drawing cycle can also be initiated when a widget itself decides
that it needs to update its display. For example, when the user that it needs to update its display. For example, when the user
types a character in a <link types a character in an entry widget, the entry asks GTK to queue
linkend="GtkEntry"><classname>GtkEntry</classname></link> a redraw operation for itself.
widget, the entry asks GTK to queue a redraw operation for
itself.
</para> </para>
<para> <para>
The windowing system generates frame events for surfaces. The GDK The windowing system generates frame events for surfaces. The GDK
interface to the windowing system translates such events into interface to the windowing system translates such events into
emissions of the #GtkSurface::render signal on the affected surfaces. emissions of the ::render signal on the affected surfaces.
The GTK toplevel window connects to that signal, and reacts appropriately. The GTK toplevel window connects to that signal, and reacts appropriately.
</para> </para>
@ -205,21 +203,21 @@
<title>Hierarchical drawing</title> <title>Hierarchical drawing</title>
<para> <para>
During the Paint phase we will send a single ::render signal the toplevel During the Paint phase GTK receives a single ::render signal on the toplevel
window. The signal handler will create a snapshot object (which is a window. The signal handler will create a snapshot object (which is a
helper for creating a scene graph) and emit a GtkWidget::snapshot() signal, helper for creating a scene graph) and emit a GtkWidget::snapshot() signal,
which will propagate down the entire widget hierarchy. This lets each widget which will propagate down the widget hierarchy. This lets each widget
snapshot its content at the right place and time, correctly handling things snapshot its content at the right place and time, correctly handling things
like partial transparencies and overlapping widgets. like partial transparencies and overlapping widgets.
</para> </para>
<para> <para>
To avoid excessive work when generating scene graphs, GTK caches render nodes. To avoid excessive work when generating scene graphs, GTK caches render nodes.
GtkWidget keeps a reference to its render node (which in turn, will refer to Each widget keeps a reference to its render node (which in turn, will refer to
the render nodes of children, and grandchildren, and so on), and will reuse the render nodes of children, and grandchildren, and so on), and will reuse
that node during the Paint phase. Invalidating a widget (e.g. by calling that node during the Paint phase. Invalidating a widget (by calling
gtk_widget_queue_draw) discards the cached render node, forcing GTK to gtk_widget_queue_draw()) discards the cached render node, forcing the widget
regenerate it the next time it needs to snapshot the widget. to regenerate it the next time it needs to handle a ::snapshot.
</para> </para>
</refsect2> </refsect2>