Function reference • ggtrace

Sub-layer stages

Take a snapshot of a layer’s data in the sub-layer pipeline

layer_before_stat() layer_after_stat() layer_before_geom() layer_after_scale(): Inspect snapshots of sub-layer data

Workflow functions

These high-level functions take a ggplot object and a function or ggproto method, allowing interactions with the ggplot’s build pipeline as it is evaluated. Functions grouped into three “workflows”: Inspect, Capture, and Highjack.

with_ggtrace(): Generic workflow function which localizes a ggtrace call to a single ggplot object

Inspect workflow

Return values from or information about a method’s execution state for inspection

ggtrace_inspect_n(): Inspect how many times a method was called

ggtrace_inspect_which(): Inspect which calls to a ggproto method met a particular condition

ggtrace_inspect_vars(): Inspect the value of variables from a method

ggtrace_inspect_args(): Inspect the arguments passed into a method

ggtrace_inspect_return(): Inspect the return value of a method

ggtrace_inspect_on_error(): Get information about a ggproto method on error

Capture workflow

Record a method’s execution state, returning it as a function or environment

ggtrace_capture_fn(): Capture a snapshot of a method as a pre-filled function

ggtrace_capture_env(): Capture a snapshot of a method's execution environment

Highjack workflow

Manipulate a method’s behavior as it runs and return the modified graphical output

ggtrace_highjack_args(): Highjack a method's execution and modify its argument values

ggtrace_highjack_return(): Highjack a method's execution and make it return a user-supplied value

Contextualize errors at the layer and sub-layer level

Return information about the (sub-)layer ggproto method that errors while rendering

last_layer_errorcontext() last_sublayer_errorcontext(): Get the internal context of the last (sub-)layer error

Extending base::trace()

The low-level function ggtrace() extends base::trace() by managing the state of injected expressions (traces), which allows for contiguity across multiple traces and the inspection of evaluated expressions logged to the tracedump, via last_ggtrace() and global_ggtrace(). Unlike the high-level workflow functions, ggtrace() relies on the “side effect” of functions and methods being traced, which can be restored with gguntrace().

Trace

Lower-level functions for finer control over injecting expressions with trace

ggtrace(): Insert traces for delayed evaluation

ggedit(): Interactively edit a masking copy of the source code

gguntrace(): Remove any existing traces

Tracedumps

Log and interact with the output of expressions injected with trace

last_ggtrace() set_last_ggtrace() clear_last_ggtrace(): Retrieve the last tracedump created by ggtrace()

global_ggtrace() set_global_ggtrace() clear_global_ggtrace() global_ggtrace_state() global_ggtrace_on() global_ggtrace_off(): Retrieve all tracedumps created by ggtrace()

Helpers

Helpers for working with ggtrace

get_method() get_method_inheritance() ggbody() ggformals(): Get information about ggproto methods

is_traced(): Check if a method is being traced

Misc

Extending other debugging tools for use with ggplot internals

ggdebug() ggdebugonce() ggundebug(): Debug a ggproto method