mu/tools/browse_trace.readme.md

A debugging helper that lets you zoom in/out on a trace.

To try it out, first create an example trace:

$ cd linux
$ bootstrap/bootstrap translate [01]*.subx factorial.subx -o factorial
$ bootstrap/bootstrap --trace run factorial

This command will save a trace of its execution in a file called last_run. The trace consists of a series of lines, each starting with an integer depth and a single-word 'label', followed by a colon and whitespace.

Now browse this trace:

$ cd ..
$ tools/browse_trace linux/last_run

You should now find yourself in a UI showing a subsequence of lines from the trace, each line starting with a numeric depth, and ending with a parenthetical count of trace lines hidden after it with greater depths.

For example, this line:

2 app: line1 (30)

indicates that it was logged with depth 2, and that 30 following lines have been hidden at a depth greater than 2.

(As an experiment, hidden counts of 1000 or more are highlighted in red.)

The UI provides the following hotkeys:

• q or ctrl-c: Quit.

• Enter: 'Zoom into' this line. Expand lines hidden after it that were at the next higher level.

• Backspace: 'Zoom out' on a line after zooming in, collapsing lines below expanded by some series of Enter commands.

• j or down-arrow: Move cursor down one line.

• k or up-arrow: Move cursor up one line.

• J or ctrl-f or page-down: Scroll cursor down one page.

• K or ctrl-b or page-up: Scroll cursor up one page.

• h or left-arrow: Scroll cursor left one character.

• l or right-arrow: Scroll cursor right one character.

• H: Scroll cursor left one screen-width.

• L: Scroll cursor right one screen-width.

• g or home: Move cursor to start of trace.

• G or end: Move cursor to end of trace.

• t: Move cursor to top line on screen.

• c: Move cursor to center line on screen.

• b: Move cursor to bottom line on screen.

• T: Scroll line at cursor to top of screen.

• /: Search forward for a pattern.

• ?: Search backward for a pattern.

• n: Repeat the previous / or ?.

• N: Repeat the previous / or ? in the opposite direction.

After hitting /, the mini-editor on the bottom-most line supports the following hotkeys:

• ascii characters: add the key to the pattern.
• Enter: search for the pattern.
• Esc or ctrl-c: cancel the current search, setting the screen back to its state before the search.
• left-arrow: move cursor left.
• right-arrow: move cursor right.
• ctrl-a or home: move cursor to start of search pattern.
• ctrl-e or end: move cursor to end of search pattern.
• ctrl-u: clear search pattern before cursor
• ctrl-k: clear search pattern at and after cursor

wish list

• Simple regular expression search: . and *.
• Expand into lower depths as necessary when searching.
• Zoom out everything.
• Zoom out lines around the cursor to the highest (or specified) depth. Maybe a number followed by ]?