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<a name="gtk-migrating-ClientSideWindows"></a>Migrating to client-side windows</h2></div></div></div>
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In version 2.18, GDK has been changed to use client-side windows. This
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means that there is no longer a 1-1 correspondence between <a href="http://library.gnome.org/devel/gdk3/gdk-Windows.html#GdkWindow"><span class="type">GdkWindows</span></a>
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means that there is no longer a 1-1 correspondence between <a href="../gdk/gdk-Windows.html#GdkWindow"><span class="type">GdkWindows</span></a>
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and windows in the underlying window system. In particular, it is no
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longer correct to assume that each window has an associated XID.
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Code that makes this assumption can sometimes be fixed by calling
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<a href="http://library.gnome.org/devel/gdk3/gdk-Windows.html#gdk-window-ensure-native"><code class="function">gdk_window_ensure_native()</code></a> on the windows in question.
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Calling <a href="http://library.gnome.org/devel/gdk3/gdk-X-Window-System-Interaction.html#gdk-x11-drawable-get-xid"><code class="function">gdk_x11_drawable_get_xid()</code></a> (or <a href="http://library.gnome.org/devel/gdk3/gdk-X-Window-System-Interaction.html#GDK-WINDOW-XID:CAPS"><code class="function">GDK_WINDOW_XID()</code></a>) from the
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<a href="../gdk/gdk-Windows.html#gdk-window-ensure-native"><code class="function">gdk_window_ensure_native()</code></a> on the windows in question.
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Calling <a href="../gdk/gdk-X-Window-System-Interaction.html#gdk-x11-drawable-get-xid"><code class="function">gdk_x11_drawable_get_xid()</code></a> (or <a href="../gdk/gdk-X-Window-System-Interaction.html#GDK-WINDOW-XID:CAPS"><code class="function">GDK_WINDOW_XID()</code></a>) from the
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X11-specific API on a non-native window will explicitly call
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<a href="http://library.gnome.org/devel/gdk3/gdk-Windows.html#gdk-window-ensure-native"><code class="function">gdk_window_ensure_native()</code></a>, so old code using this will continue to
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work. A small gotcha is that the <a href="http://library.gnome.org/devel/gdk3/gdk-X-Window-System-Interaction.html#GDK-WINDOW-XID:CAPS"><code class="function">GDK_WINDOW_XID()</code></a> call is no longer a
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<a href="../gdk/gdk-Windows.html#gdk-window-ensure-native"><code class="function">gdk_window_ensure_native()</code></a>, so old code using this will continue to
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work. A small gotcha is that the <a href="../gdk/gdk-X-Window-System-Interaction.html#GDK-WINDOW-XID:CAPS"><code class="function">GDK_WINDOW_XID()</code></a> call is no longer a
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trivial accessor for the XID of the window, and thus must not be called
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from another thread without taking locking precautions.
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using <code class="function">XRestackWindows()</code>. Fixing this properly requires to fix the code
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to use GDK functions to achieve whatever it is trying to achieve.
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To make this easier in the case of stacking order changes, we've added
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a <a href="http://library.gnome.org/devel/gdk3/gdk-Windows.html#gdk-window-restack"><code class="function">gdk_window_restack()</code></a> function.
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a <a href="../gdk/gdk-Windows.html#gdk-window-restack"><code class="function">gdk_window_restack()</code></a> function.
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One change that can cause problems for some applications is that GDK
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Problems can also occur when using cairo for drawing. One thing that can
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go wrong is clip handling. If you ever need to reset the clip region on
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a cairo_t (i.e. use <a href="/home/mclasen/gnome-3.0/install/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-reset-clip"><code class="function">cairo_reset_clip()</code></a>), you have to to use
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<a href="http://library.gnome.org/devel/gdk3/gdk-Cairo-Interaction.html#gdk-cairo-reset-clip"><code class="function">gdk_cairo_reset_clip()</code></a> instead. The reason for this is that the <a href="/home/mclasen/gnome-3.0/install/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-reset-clip"><code class="function">cairo_reset_clip()</code></a> call will remove the initial clip region that limits your drawing to
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a cairo_t (i.e. use <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-reset-clip"><code class="function">cairo_reset_clip()</code></a>), you have to to use
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<a href="../gdk/gdk-Cairo-Interaction.html#gdk-cairo-reset-clip"><code class="function">gdk_cairo_reset_clip()</code></a> instead. The reason for this is that the <a href="/usr/share/gtk-doc/html/cairo/cairo-cairo-t.html#cairo-reset-clip"><code class="function">cairo_reset_clip()</code></a> call will remove the initial clip region that limits your drawing to
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the client-side window at hand, so you will end up drawing over stuff
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outside the window. You also need to use <a href="http://library.gnome.org/devel/gdk3/gdk-Cairo-Interaction.html#gdk-cairo-reset-clip"><code class="function">gdk_cairo_reset_clip()</code></a> if you
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outside the window. You also need to use <a href="../gdk/gdk-Cairo-Interaction.html#gdk-cairo-reset-clip"><code class="function">gdk_cairo_reset_clip()</code></a> if you
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use a cairo_t that was not allocated in a double-buffered expose handler
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and keep it in use after window hierarchy changes (resizing, moving,
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stacking order changes). The easiest fix for this kind of problem is to
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simply create a new cairo context for each expose event.
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Due to a weird API in XClearArea the <a href="http://library.gnome.org/devel/gdk3/gdk-Windows.html#gdk-window-clear-area"><code class="function">gdk_window_clear_area()</code></a> call handled
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Due to a weird API in XClearArea the <a href="../gdk/gdk-Windows.html#gdk-window-clear-area"><code class="function">gdk_window_clear_area()</code></a> call handled
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a specified width or height of zero to mean "to end of window" for
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non-double-buffered drawing. This has been changed to be consistent with
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the docs and what happens in the double-buffered case. All code in GTK+
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that relied on this has been fixed, but it is possible (although unlikely)
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that third party applications rely on this. If you need to do this, just
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implement it yourself using <a href="http://library.gnome.org/devel/gdk3/gdk-Drawing-Primitives.html#gdk-drawable-get-size"><code class="function">gdk_drawable_get_size()</code></a>.
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implement it yourself using <a href="../gdk/gdk-Drawing-Primitives.html#gdk-drawable-get-size"><code class="function">gdk_drawable_get_size()</code></a>.
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