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cookbook: Cleaning up grammar and wording in mouse scroll recipe
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@ -347,13 +347,14 @@ clutter_stage_set_key_focus (stage, actor);
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</section>
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</section>
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<section id="events-mouse-scroll">
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<section id="events-mouse-scroll">
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<title>Detecting mouse wheel scrolling on an actor</title>
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<title>Detecting mouse scrolling on an actor</title>
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<section>
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<section>
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<title>Problem</title>
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<title>Problem</title>
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<para>You want to detect when the mouse wheel is scrolled on an
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<para>You want to detect when the mouse is scrolled on an
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actor.</para>
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actor (e.g. the pointer is over an actor when a mouse
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wheel is scrolled).</para>
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</section>
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</section>
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<section>
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<section>
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@ -373,21 +374,7 @@ clutter_actor_set_reactive (actor, TRUE);
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</programlisting>
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</programlisting>
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</informalexample>
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</informalexample>
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<para>Next, connect a callback handler to the
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<para>Next, create a callback handler to examine the scroll
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<code>scroll-event</code> signal of the actor:</para>
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<informalexample>
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<programlisting>
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<![CDATA[
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g_signal_connect (actor,
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"scroll-event",
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G_CALLBACK (_scroll_event_cb),
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NULL);
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]]>
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</programlisting>
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</informalexample>
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<para>Finally, create a callback handler to examine the scroll
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event and respond to it:</para>
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event and respond to it:</para>
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<informalexample>
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<informalexample>
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@ -398,7 +385,7 @@ _scroll_event_cb (ClutterActor *actor,
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ClutterEvent *event,
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ClutterEvent *event,
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gpointer user_data)
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gpointer user_data)
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{
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{
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/* determine the direction the mouse wheel was scrolled */
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/* determine the direction the mouse was scrolled */
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ClutterScrollDirection direction;
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ClutterScrollDirection direction;
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direction = clutter_event_get_scroll_direction (event);
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direction = clutter_event_get_scroll_direction (event);
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@ -424,6 +411,21 @@ _scroll_event_cb (ClutterActor *actor,
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]]>
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]]>
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</programlisting>
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</programlisting>
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</informalexample>
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</informalexample>
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<para>Finally, connect the callback handler to the
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<code>scroll-event</code> signal of the actor:</para>
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<informalexample>
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<programlisting>
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<![CDATA[
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g_signal_connect (actor,
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"scroll-event",
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G_CALLBACK (_scroll_event_cb),
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NULL);
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]]>
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</programlisting>
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</informalexample>
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</section>
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</section>
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<section>
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<section>
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@ -431,8 +433,8 @@ _scroll_event_cb (ClutterActor *actor,
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<para>A standard mouse wheel will only return up and
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<para>A standard mouse wheel will only return up and
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down movements; but in cases where the mouse has left and
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down movements; but in cases where the mouse has left and
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right scrolling (e.g. a trackball mouse), left and right scroll
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right scrolling (e.g. a trackball mouse or trackpad), left and
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events may also be emitted.</para>
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right scroll events may also be emitted.</para>
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<section>
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<section>
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<title>Creating a scrolling viewport for an actor</title>
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<title>Creating a scrolling viewport for an actor</title>
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@ -475,7 +477,7 @@ _scroll_event_cb (ClutterActor *actor,
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<orderedlist>
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<orderedlist>
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<listitem>
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<listitem>
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<para>Create the scrollable actor; it should be larger
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<para>Create the scrollable actor; it should be larger
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than the scrollview. This example uses a <type>ClutterTexture</type>,
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than the viewport. This example uses a <type>ClutterTexture</type>,
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but any <type>ClutterActor</type> will work:</para>
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but any <type>ClutterActor</type> will work:</para>
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<informalexample>
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<informalexample>
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<programlisting>
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<programlisting>
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@ -488,14 +490,15 @@ clutter_texture_set_keep_aspect_ratio (CLUTTER_TEXTURE (texture),
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/*
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/*
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* set the texture's height so it's as tall as the stage
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* set the texture's height so it's as tall as the stage
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* (STAGE_HEIGHT is define'd at the top of the file);
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* (STAGE_HEIGHT is define'd at the top of the file)
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* see <link linkend="textures-aspect-ratio">this recipe</link>
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* for more about loading images into textures
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*/
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*/
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clutter_actor_set_request_mode (texture, CLUTTER_REQUEST_WIDTH_FOR_HEIGHT);
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clutter_actor_set_request_mode (texture, CLUTTER_REQUEST_WIDTH_FOR_HEIGHT);
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clutter_actor_set_height (texture, STAGE_HEIGHT);
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clutter_actor_set_height (texture, STAGE_HEIGHT);
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/* load the image file */
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/*
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* load the image file;
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* see <link linkend="textures-aspect-ratio">this recipe</link> for more about loading images into textures
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*/
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clutter_texture_set_from_file (CLUTTER_TEXTURE (texture),
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clutter_texture_set_from_file (CLUTTER_TEXTURE (texture),
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image_file_path,
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image_file_path,
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NULL);
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NULL);
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@ -533,17 +536,17 @@ clutter_actor_set_clip_to_allocation (viewport, TRUE);
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<para>The key here is calling
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<para>The key here is calling
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<code>clutter_actor_set_clip_to_allocation (viewport, TRUE)</code>.
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<code>clutter_actor_set_clip_to_allocation (viewport, TRUE)</code>.
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This configures the <varname>viewport</varname> group so
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This configures the <varname>viewport</varname> group so
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that any of its children are clipped: i.e. only the area of
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that any of its children are clipped: i.e. only parts of
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the children which fits inside the group is visible. This
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its children which fit inside its allocation are visible. This
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in turn requires setting an explicit size on the group,
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in turn requires setting an explicit size on the group,
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rather than allowing it to size itself to fit its
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rather than allowing it to size itself to fit its
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children (the default).</para>
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children (the latter is the default).</para>
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</listitem>
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</listitem>
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<listitem>
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<listitem>
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<para>Put the scrollable actor into the scroll view and
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<para>Put the scrollable actor into the viewport; and
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the scroll view into its container (in this case,
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the viewport into its container (in this case,
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the default stage):</para>
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the default stage):</para>
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<informalexample>
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<informalexample>
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@ -557,8 +560,8 @@ clutter_container_add_actor (CLUTTER_CONTAINER (stage), viewport);
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</listitem>
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</listitem>
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<listitem>
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<listitem>
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<para>Create a callback handler for scroll event signals
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<para>Create a callback handler for <code>scroll-event</code>
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emitted by the viewport:</para>
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signals emitted by the viewport:</para>
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<informalexample>
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<informalexample>
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<programlisting>
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<programlisting>
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@ -625,15 +628,15 @@ _scroll_event_cb (ClutterActor *viewport,
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<para>The approach taken here is to move the scrollable
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<para>The approach taken here is to move the scrollable
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actor up, relative to the viewport. Initially, the
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actor up, relative to the viewport. Initially, the
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scrollable will have a <code>y</code> coordinate value
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scrollable will have a <code>y</code> coordinate value
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of <code>0.0</code> (it is aligned to the top of the viewport).
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of <code>0.0</code> (aligned to the top of the viewport).
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Scrolling up subtracts from the
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Scrolling up decrements the
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<code>y</code> coordinate (down to a minumum of
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<code>y</code> coordinate (down to a minumum of
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<code>viewport_height - scrollable_height</code>). This moves
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<code>viewport_height - scrollable_height</code>). This moves
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the top of the scrollable "outside" the clip area of the
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the top of the scrollable actor "outside" the clip area of the
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viewport; simultaneously, more of the bottom part of the
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viewport; simultaneously, more of the bottom part of the
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scrollable moves into the clip area, becoming visible.</para>
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scrollable moves into the clip area, becoming visible.</para>
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<para>Scrolling down adds to the <code>y</code> coordinate
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<para>Scrolling down increments the <code>y</code> coordinate
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(but only up to a maximum value of <code>0.0</code>).</para>
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(but only up to a maximum value of <code>0.0</code>).</para>
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<para>To see how this works in practice, look at
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<para>To see how this works in practice, look at
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@ -642,16 +645,17 @@ _scroll_event_cb (ClutterActor *viewport,
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set to <code>300</code> and the height of the viewport to
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set to <code>300</code> and the height of the viewport to
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<code>150</code>. This means that the <code>y</code>
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<code>150</code>. This means that the <code>y</code>
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coordinate value for the scrollable actor will vary between
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coordinate value for the scrollable actor will vary between
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<code>-150.0</code> (<code>150 - 300</code>), making
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<code>-150.0</code>: <code>150</code> (the viewport's height)
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its base visible and clipping the top; and
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<code>- 300</code> (the scrollable actor's height), making
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its base visible and clipping its top; and
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<code>0.0</code>, where its top is visible and its base
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<code>0.0</code>, where its top is visible and its base
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clipped.</para>
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clipped.</para>
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</listitem>
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</listitem>
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<listitem>
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<listitem>
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<para>Connect the callback handler to the signal; note
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<para>Connect the callback handler to the signal; note
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that we pass the scrollable (the texture) to the callback,
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that we pass the scrollable actor (the texture) to the callback,
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as we're moving the texture inside the viewport to
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as we're moving the texture relative to the viewport to
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create the scrolling effect:</para>
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create the scrolling effect:</para>
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<informalexample>
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<informalexample>
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