<doc>
  <legacy_id>1633</legacy_id>
  <name>constantMask</name>
  <type>property</type>
  <syntax>
    <example>set the constantMask of <i>image</i> to {true | false}</example>
  </syntax>
  <library></library>
  <objects>
    <image/>
  </objects>
  <synonyms>
  </synonyms>
  <classification>
    <category>Images &amp; Multimedia</category>
  </classification>
  <references>
    <property tag="filename">filename Property</property>
    <property tag="imagePixmapID">imagePixmapID Property</property>
    <property tag="alwaysBuffer">alwaysBuffer Property</property>
  </references>
  <history>
    <introduced version="1.0">Added.</introduced>
  </history>
  <platforms>
    <mac/>
    <windows/>
    <linux/>
    <ios/>
    <android/>
  </platforms>
  <classes>
    <desktop/>
    <server/>
    <web/>
    <mobile/>
  </classes>
  <security>
  </security>
  <summary>Specifies whether <glossary tag="animated GIF">animated GIFs</glossary> ignore changes in the <glossary tag="mask">mask</glossary> data when displaying the <glossary tag="GIF">GIF</glossary>.</summary>
  <examples>
    <example>set the constantMask of image "Demo" to true</example>
  </examples>
  <description>
    <p>Use the <b>constantMask</b> <glossary tag="property">property</glossary> to enable display of certain <glossary tag="animated GIF">animated GIF</glossary> <glossary tag="image">images</glossary>.</p><p/><p><b>Value:</b></p><p>The <b>constantMask</b> of an <keyword tag="image">image</keyword> is true or false.</p><p/><p>By default, the <b>constantMask</b> <glossary tag="property">property</glossary> of newly created <glossary tag="image">images</glossary> is set to false.</p><p/><p><b>Comments:</b></p><p>Some animated GIF images use an optimization technique in which the mask data is used to hold information about differences between successive frames. When played, these GIFs can have display problems because the mask data is being used in a non-standard way. Set the <b>constantMask</b> to true to correct the problem with these <glossary tag="GIF">GIFs</glossary>.</p><p/><p>Setting the <b>constantMask</b> to true may have some undesirable side effects--the <glossary tag="image">image's</glossary> appearance may be incorrect if you move it while the animation is playing, or if there is an <glossary tag="object">object</glossary> underneath it--so use this <glossary tag="property">property</glossary> only when necessary.</p><p/><p><code/><b>Note:</b><code/> If the <b>constantMask</b> is set to true, clicking a transparent portion of a <glossary tag="frame">frame</glossary> may unexpectedly send <glossary tag="message">messages</glossary> such as <message tag="mouseUp">mouseUp</message> to the <keyword tag="image">image</keyword>, instead of the <glossary tag="object">object</glossary> underneath the <keyword tag="image">image</keyword>. This is because when deciding whether the user has clicked a transparent <glossary tag="pixel">pixel</glossary>, LiveCode uses the <glossary tag="mask">masks</glossary> for all the <glossary tag="frame">frames</glossary>, rather than for the current <glossary tag="frame">frame</glossary>, if the <b>constantMask</b> is true.</p><p/><p><code/><img src="202653"/> <b>Important!</b><code/> Setting an <glossary tag="image">image's</glossary> <b>constantMask</b> <glossary tag="property">property</glossary> to true can cause problems with the <glossary tag="image">image's</glossary> appearance if you move it under <property tag="script">script</property> control while the animation is playing, or if there's an <glossary tag="object">object</glossary> underneath it. Avoid setting the <property tag="constantMask">constantMask</property> <glossary tag="property">property</glossary> to true unless necessary.</p>
  </description>
</doc>