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Ensure drawing context is set

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If somebody decides to use gtk_widget_set_double_buffered() in the
middle of a draw() then there's the risk of calling end_draw_frame()
with an invalid pointer.

Some overeager compilers may warn about the double_buffered bit field
changing values and leading to a potentially uninitialized variable.

In order to avoid compiler warnings or crashes, we can simply store the
value of the double_buffered bit field at the beginning of the rendering
and use that instead of the actual bit field.

https://bugzilla.gnome.org/show_bug.cgi?id=771463
This commit is contained in:
Emmanuele Bassi 2016-09-15 10:05:05 +01:00
parent 638c3e2e6b
commit bb705837bc
1 changed files with 8 additions and 2 deletions
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10
gtk/gtkwidget.c
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@ -17464,8 +17464,14 @@ gtk_widget_render (GtkWidget *widget,
gboolean do_clip;
cairo_t *cr;
int x, y;
gboolean is_double_buffered;
if (priv->double_buffered)
/* We take the value here, in case somebody manages to changes
* the double_buffered value inside a ::draw call, and ends up
* breaking everything.
*/
is_double_buffered = priv->double_buffered;
if (is_double_buffered)
{
/* We only render double buffered on native windows */
if (!gdk_window_has_native (window))
@ -17492,7 +17498,7 @@ G_GNUC_END_IGNORE_DEPRECATIONS
gtk_widget_draw_internal (widget, cr, do_clip);
if (priv->double_buffered)
if (is_double_buffered)
gdk_window_end_draw_frame (window, context);
else
cairo_destroy (cr);