Debugging

Trial includes a variety of tools to aid in the inevitable debugging process.

Logging

Trial relies on the Verbose logger framework to print various status messages to its log. You can, of course, make use of all of Verbose's features yourself as well. You should add a local nickname for org.shirakumo.verbose (as v) to your package definitions for that.

When deployed, Trial will also automatically capture Verbose's log to a logfile that can be used for debugging crashes and other issues.

Trial also offers a number of useful shorthand macros:

• with-error-logging
  Will log any unhandled error that is signalled within the body.

• with-ignored-errors-on-release
  Does the same as with-error-logging but ignoring the error in release mode and propagating it to the debugger with a continue restart in development mode.

• with-timing-report
  Logs a report on the time taken to execute the body.

Watches

You can add a watchpoint for the result of a function with the observe function, or of an expression with the observe! macro. To remove the watchpoint again, you can use stop-observing.

In order for the watches to show up, you must have a display-controller in your scene. Typically you'll want to do this by using (enter (make-instance 'display-controller) scene) in your setup-scene.

You can also use an fps-counter instance to only observe the frame count. The fps-counter in particular is written to be as low latency as possible, and should have almost zero overhead.

Drawing

In order to debug visual information, you can use the following functions:

• debug-point
  Draws a point at the specified coordinate.

• debug-line
  Draws a line between the specified points.

• debug-text
  Shows the text at the specified point. The text can only contain ASCII characters.

• debug-triangles
  Draw a set of triangles as a line mesh.

• debug-vertex-array
  Draw a vertex array as a line mesh. This should work regardless of primitive shape used.

• debug-clear
  Clear all debug draws.

• debug-draw
  Generic version that dispatches to the above depending on the argument.

All of these are copying, meaning they won't update if their arguments are modified and they'll stick around until cleared away. All of the functions also accept the following arguments:

• :color
  The color of the lines or point.

• :debug-draw
  The debug-draw instance used to draw the elements. Defaults to using an entity named debug-draw and will create one if it doesn't exist yet.

• :update
  Whether the data should be uploaded to the GPU immediately. You may want to set this to NIL if you intend on drawing a large batch of debug info.

Note that all drawing calls are synchronised to the render thread. Meaning that if the call occurs outside of the render thread, it is scheduled asynchronously to run on it.

Renderdoc

Special mention should be made of the Renderdoc tool. While Trial allows redefinition of shaders at runtime, sometimes being able to capture the entire pipeline state and inspect it can be invaluable to figure out weird graphical issues. Renderdoc is ideal for this situation and works fine with Trial, as long as the underlying lisp process is called via Renderdoc.

To do so, create a small script like so:

(ql:quickload :swank)
(swank:create-server)
(ql:quickload :my-project)
(my-project::launch)

Then you can configure your implementation as a launch option in Rendedoc:

• Executable Path Eg: /usr/bin/sbcl

• Command-line Arguments Eg: --load /tmp/renderdoc.lisp

Launching it like that should allow you to connect via Slime on port 4005, and capture snapshots of the running process via Renderdoc.