Increase the value of a variable being passed to call-template - xslt

Question

I have the following bit of xsl inside a template:
<xsl:variable name="current_x" select="position_x" />
<xsl:variable name="current_y" select="position_y" />
<xsl:if test="units_display='true'">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value"><xsl:value-of select="units" /></xsl:with-param>
<xsl:with-param name="text" select="'Units'" />
</xsl:call-template>
</xsl:if>
<xsl:if test="sensor_display='true'">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value"><xsl:value-of select="sensor" /></xsl:with-param>
<xsl:with-param name="text" select="'Type'" />
</xsl:call-template>
</xsl:if>
My call-template is like this:
<xsl:template name="DisplayBox">
<xsl:param name="current_x" select="0"/>
<xsl:param name="current_y" select="0"/>
<xsl:param name="value" />
<xsl:param name="text" />
<g transform="translate({$current_x},{$current_y})">
<rect x="20" y="150" width="220" height="20" fill="#FFFFFF" stroke="black" stroke-width="1" />
<text x="25" y="168" font-family="arial" font-size="20px" fill="black">
<xsl:value-of select="$value"/>
</text>
<line x1="90" y1="150" x2="90" y2="170" stroke="black" stroke-width="1" />
<text x="95" y="168" font-family="arial" font-size="20px" fill="black">
<xsl:value-of select="$text" />
</text>
</g>
</xsl:template>
This displays the value of 'value' and 'text' inside a rectangle. The thing I cannot work out how to do, however, is to not have them write on top of each other. I want to increase the current_y value if the test="xxxx_display=true. But I am at a loss of how to achieve this.
I can't work out how I can increase the value of current_y outside of the call-template.
EDIT:
There seems to be a problem in using transform translate in the call-template. It seems to ignore those values.
I have modded the code to now be:
<xsl:if test="units_display='true'">
<g transform="translate({position_x},{position_y})">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value">
<xsl:value-of select="units" />
</xsl:with-param>
<xsl:with-param name="text" select="'Units'" />
</xsl:call-template>
</g>
</xsl:if>
<xsl:if test="sensor_display='true'">
<g transform="translate({position_x},{position_y + 20})">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value">
<xsl:value-of select="sensor" />
</xsl:with-param>
<xsl:with-param name="text" select="'Type'" />
</xsl:call-template>
</g>
</xsl:if>
But, I don't want to hard-code 'position_y + 20'. I would like the 2nd value to be at position_y if the first value display was not true, but the 2nd value to be at position_y + 20 if the first value display was true. This must be possible somehow I would hope.

Answer 1

By the way, don't do this:
<xsl:with-param name="value"><xsl:value-of select="sensor" /></xsl:with-param>
when you mean this:
<xsl:with-param name="value" select="sensor" />
It's not only verbose, it's also incredibly inefficient: instead of simply passing a reference to a value, you are constructing a temporary tree containing a text node that holds a copy of the value. Creating new trees is an expensive operation.

Answer 2

Simply pass the the parameters current_x and current_y with the adjusted values like this:
<xsl:if test="units_display='true'">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value"><xsl:value-of select="units" /></xsl:with-param>
<xsl:with-param name="text" select="'Units'" />
<xsl:with-param name="current_x" select="position_x"/>
<xsl:with-param name="current_y" select="position_y + 100"/>
</xsl:call-template>
</xsl:if>
<xsl:if test="sensor_display='true'">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value"><xsl:value-of select="sensor" /></xsl:with-param>
<xsl:with-param name="text" select="'Type'" />
<xsl:with-param name="current_x" select="position_x"/>
<xsl:with-param name="current_y" select="position_y + 200"/>
</xsl:call-template>
</xsl:if>
EDIT: If you want to go with the second approach, try to change the sensor_display part to:
<xsl:if test="sensor_display='true'">
<xsl:variable name="offset">
<xsl:choose>
<xsl:when test="units_display='true'">20</xsl:when>
<xsl:otherwise>0</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<g transform="translate({position_x},{position_y + $offset})">
<xsl:call-template name="DisplayBox">
<xsl:with-param name="value">
<xsl:value-of select="sensor" />
</xsl:with-param>
<xsl:with-param name="text" select="'Type'" />
</xsl:call-template>
</g>
</xsl:if>
BTW, if you rephrase your question like this, it's better to start a new question.