Trying to create a custom instruments (without CLIPS right now), and I think I have the patterns hooked up correctly, but no data is appearing.

Debugging a Custom Instrument

Writing a custom instrument.

Have this in code in the app


```
@implementation MJSignpost


+ (os_log_t) log {
    static os_log_t log;
    if (log == 0) {
        // can try different categories
        log = os_log_create("com.appname.signposts", "MusicLayout");
    }
    return log;

} // log

@end

// ...
  os_signpost_interval_begin(MJSignpost.log,
                                   OS_SIGNPOST_ID_EXCLUSIVE,
                                   "Space Measure",
                                   "Spacing measure %{xcode:int64}llu",
                                   (unsigned long long)measureIndex);
// do something pretty expensive
        NSInteger elementCount = // calculate a weight
        os_signpost_interval_end(MJSignpost.log,
                                 OS_SIGNPOST_ID_EXCLUSIVE,
                                 "Space Measure",
                                 "Finished Spacing stack count %{xcode:uint64}llu",
                                 (unsigned long long)elementCount);
```

and have this XML file

```
<?xml version="1.0" encoding="UTF-8" ?>
<package>
    <id>com.appname.Layout-Instruments</id>
    <title>Layout Instruments</title>
    <owner>
        <name>App Name</name>
    </owner>
    
    <os-signpost-interval-schema>
        <id>space-measure</id>
        <title>Spacing Measure</title>
        
        <subsystem>"com.appname.signposts"</subsystem>
        <category>"MusicLayout"</category>
        <name>"Spacing Measures"</name>
        
        <start-pattern>
            <message>"Spacing measure " ?measure-index</message>
        </start-pattern>
        <end-pattern>
            <message>"Finished Spacing stack count " ?measure-elements</message>
        </end-pattern>
        
        <column>
            <mnemonic>measure-index</mnemonic>
            <title>Index</title>
            <type>uint64</type>
            <expression>?measure-index</expression>
        </column>
        <column>
            <mnemonic>measure-elements</mnemonic>
            <title>Elements</title>
            <type>uint64</type>
            <expression>?measure-elements</expression>
        </column>
        <column>
            <mnemonic>impact</mnemonic>
            <title>Impact</title>
            <type>event-concept</type>
            <expression>(if (&gt; ?measure-elements 50) then "High" else "Low")</expression> <!-- c.f. https://help.apple.com/instruments/developer/mac/current/#/dev66257045 -->
        </column>
    </os-signpost-interval-schema>
    
        
    <instrument>
        <id>com.appname.signposts-layout</id>
        
        <title>MusicJot Layout</title>
        <category>Behavior</category>
        <purpose>Profile score layout work</purpose>
        <icon>Generic</icon>
        
        <create-table>
            <id>space-measures</id>
            <schema-ref>space-measure</schema-ref>
        </create-table>
        
        <!-- Define graph to draw for your Instrument (optional) -->
        <graph>
            <title>Measure Spacing</title>
            <lane>
                <title>Measures</title>
                <table-ref>space-measures</table-ref>
                <plot-template>
                    <instance-by>measure-index</instance-by>
                    <label-format>%d</label-format>
                    <value-from>impact</value-from>
                    <label-from>measure-elements</label-from>
                    <disable-implicit-qualifier>true</disable-implicit-qualifier>  <!-- Disables the implicit use of layout information in the table. _not terribly useful -->
                </plot-template>
            </lane>
        </graph>
        
        <!-- Define at least one detail view for your Instrument -->
        <list>
            <title>Measure Layout</title>
            <table-ref>space-measures</table-ref>
            <column>start</column>
            <column>duration</column>
            <column>measure-index</column>
            <column>measure-elements</column>
        </list>
        
        <aggregation>
            <title>Summary: Elements</title>
            <table-ref>space-measures</table-ref>
            
            <hierarchy>
                <level>
                    <column>measure-index</column>
                </level>
            </hierarchy>
            
            <column>
                <count />
            </column>
            <column>
                <sum>measure-elements</sum>
            </column>
        </aggregation>
        
        <time-slice>
            <title>Time Slice: Elements</title>
            <table-ref>space-measures</table-ref>
            <column>start</column>
            <column>duration</column>
            <column>measure-index</column>
            <column>measure-elements</column>
        </time-slice>
    </instrument>
 </package>
```

I'm seeing the sign post data coming in to instruments, but nothing is appearing in the lane.

In the os_signpost table I'm seeing:

```
V Space Measure
    V Spacing measure 1
        Finished Spacing stack count 495
    V Spacing measure 2
        Finished Spacing stack count 495
```
Not sure how to approach debugging this. Looking in the instrument info panel, the schema is there, and the table has zero rows.