.. _user_interfaces-svg_tooltip:

user_interfaces example code: svg_tooltip.py
============================================

[`source code <svg_tooltip.py>`_]

::

    """
    SVG tooltip example
    ===================
    
    This example shows how to create a tooltip that will show up when
    hovering over a matplotlib patch.
    
    Although it is possible to create the tooltip from CSS or javascript,
    here we create it in matplotlib and simply toggle its visibility on
    when hovering over the patch. This approach provides total control over
    the tooltip placement and appearance, at the expense of more code up
    front.
    
    The alternative approach would be to put the tooltip content in `title`
    atttributes of SVG objects. Then, using an existing js/CSS library, it
    would be relatively straightforward to create the tooltip in the
    browser. The content would be dictated by the `title` attribute, and
    the appearance by the CSS.
    
    
    :author: David Huard
    """
    
    
    import matplotlib.pyplot as plt
    import xml.etree.ElementTree as ET
    from StringIO import StringIO
    
    ET.register_namespace("","http://www.w3.org/2000/svg")
    
    fig, ax = plt.subplots()
    
    # Create patches to which tooltips will be assigned.
    circle = plt.Circle((0,0), 5, fc='blue')
    rect = plt.Rectangle((-5, 10), 10, 5, fc='green')
    
    ax.add_patch(circle)
    ax.add_patch(rect)
    
    # Create the tooltips
    circle_tip = ax.annotate('This is a blue circle.',
                xy=(0,0),
                xytext=(30,-30),
                textcoords='offset points',
                color='w',
                ha='left',
                bbox=dict(boxstyle='round,pad=.5', fc=(.1,.1,.1,.92), ec=(1.,1.,1.), lw=1, zorder=1),
                )
    
    rect_tip = ax.annotate('This is a green rectangle.',
                xy=(-5,10),
                xytext=(30,40),
                textcoords='offset points',
                color='w',
                ha='left',
                bbox=dict(boxstyle='round,pad=.5', fc=(.1,.1,.1,.92), ec=(1.,1.,1.), lw=1, zorder=1),
                )
    
    
    # Set id for the patches
    for i, t in enumerate(ax.patches):
        t.set_gid('patch_%d'%i)
    
    # Set id for the annotations
    for i, t in enumerate(ax.texts):
        t.set_gid('tooltip_%d'%i)
    
    
    # Save the figure in a fake file object
    ax.set_xlim(-30, 30)
    ax.set_ylim(-30, 30)
    ax.set_aspect('equal')
    
    f = StringIO()
    plt.savefig(f, format="svg")
    
    # --- Add interactivity ---
    
    # Create XML tree from the SVG file.
    tree, xmlid = ET.XMLID(f.getvalue())
    tree.set('onload', 'init(evt)')
    
    # Hide the tooltips
    for i, t in enumerate(ax.texts):
        el = xmlid['tooltip_%d'%i]
        el.set('visibility', 'hidden')
    
    # Assign onmouseover and onmouseout callbacks to patches.
    for i, t in enumerate(ax.patches):
        el = xmlid['patch_%d'%i]
        el.set('onmouseover', "ShowTooltip(this)")
        el.set('onmouseout', "HideTooltip(this)")
    
    # This is the script defining the ShowTooltip and HideTooltip functions.
    script = """
        <script type="text/ecmascript">
        <![CDATA[
    
        function init(evt) {
            if ( window.svgDocument == null ) {
                svgDocument = evt.target.ownerDocument;
                }
            }
    
        function ShowTooltip(obj) {
            var cur = obj.id.slice(-1);
    
            var tip = svgDocument.getElementById('tooltip_' + cur);
            tip.setAttribute('visibility',"visible")
            }
    
        function HideTooltip(obj) {
            var cur = obj.id.slice(-1);
            var tip = svgDocument.getElementById('tooltip_' + cur);
            tip.setAttribute('visibility',"hidden")
            }
    
        ]]>
        </script>
        """
    
    # Insert the script at the top of the file and save it.
    tree.insert(0, ET.XML(script))
    ET.ElementTree(tree).write('svg_tooltip.svg')
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)