docs/html/tools/performance/debug-gpu-overdraw/index.jd

page.title=Debug GPU Overdraw Walkthrough
meta.tags="android, performance, profiling, tools, rendering, overdraw"
page.tags="android", "performance", "profiling", "tools",  "rendering", "overdraw"
page.metaDescription=Use color-coding to show how many times each pixel is redrawn on the screen to reduce rendering overhead.
page.image=tools/performance/thumbnails/tools_debug_gpu_overdraw.png
page.article=true


@jd:body

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<h2>In this document</h2>
<ul>
  <li><a href="#WhatYouNeed">Prerequisites</a></li>
  <li><a href="#VisualizingOverdraw">Visualizing Overdraw</a></li>
</ul>

<h2>You should also read</h2>
<ul>
  <li><a href="{@docRoot}tools/performance/profile-gpu-rendering/index.html">
    Profile GPU Rendering Walkthrough</a></li>
  <li><a href="{@docRoot}tools/performance/hierarchy-viewer/index.html">
    Hierarchy Viewer Walkthrough</a></li>
</ul>

</div>

  <p>This walkthrough shows how to visualize overdraw on your mobile device by color-coding
  interface elements based on how often they are drawn underneath.</p>

  <p>What it's good for:</p>

  <ul>
    <li>Showing where an app might be doing more rendering work than necessary.</li>

    <li>Helping you see where you might be able to reduce rendering overhead.</li>
  </ul>

  <h2 id="WhatYouNeed">Prerequisites</h2>

  <ul>
    <li>A mobile device with <a href=
    "http://developer.android.com/tools/device.html#developer-device-options">Developer Options</a>
    enabled.</li>
  </ul>


  <h2 id="VisualizingOverdraw">Visualizing Overdraw on your Mobile Device</h2>

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  <ol class="padded">

    <div class="figure" style="">
      <img
    src="{@docRoot}images/tools/performance/debug-gpu-overdraw/gettingstarted_image01.png"
         alt=""
         width="400px" />
      <p class="img-caption">
        <strong>Figure 1. </strong>Steps for turning on Debug GPU Overdraw.
      </p>
    </div>

    <li>On your mobile device, go to <b>Settings</b> and tap <b>Developer Options</b>.</li>

    <li>In the <em>Hardware accelerated rendering</em> section,
      select <b>Debug GPU Overdraw</b>.</li>

    <li>In the <b>Debug GPU overdraw</b> popup, select <b>Show overdraw areas</b>.</li>
 </ol>
</div></li>

<li><div style="overflow:hidden">
<hr>
  <ol class="padded" start="5">

     <div class="figure" style="padding-right:100px">
      <img
    src="{@docRoot}images/tools/performance/debug-gpu-overdraw/gettingstarted_image02.png"
         alt=""
         width="180px" />
      <p class="img-caption">
        <strong>Figure 2. </strong>Example of<br>Debug GPU Overdraw output.
      </p>
    </div>

    <li>Don't panic as your screen turns into a delirium of colors.
      The coloring is provided to help you diagnose your app's display behavior.</li>

  </ol>
</div></li>

<li><div style="overflow:hidden">
<hr>
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     <div class="figure" style="">
      <img
    src="{@docRoot}images/tools/performance/debug-gpu-overdraw/gettingstarted_image03.png"
         alt=""
         width="300px" />
      <p class="img-caption">
        <strong>Figure 3. </strong>Color key for Debug GPU Overdraw output.
      </p>
    </div>

    <br><br>
    <li>The colors are hinting at the amount of overdraw on your screen for each pixel, as
      follows:

      <ul>
        <li><b>True color:</b> No overdraw</li>
        <li><b>Blue:</b> Overdrawn once</li>
        <li><b>Green:</b> Overdrawn twice</li>
        <li><b>Pink:</b> Overdrawn three times</li>
        <li><b>Red:</b> Overdrawn four or more times</li>
      </ul>
    </li>

</ol>
</div></li>

<li><div style="overflow:hidden">
<hr>
 <ol class="padded" start="7">

    <div class="figure" style="">
      <img
    src="{@docRoot}images/tools/performance/debug-gpu-overdraw/gettingstarted_image04.png"
         alt=""
         width="300px" />
      <p class="img-caption">
        <strong>Figure 4. </strong>Examples of undesirable and desirable
          <br>Debug GPU Overdraw output.
      </p>
    </div>

    <br><br><br>
    <li>Some overdraw is unavoidable. As you are tuning your app's
      user interface, the goal is to arrive at a visualization that shows mostly true
      colors and 1X overdraw in blue.</li>

  </ol>
</div></li>
</ul>