ExoTracker Newsletter #1

I just finished implementing timeline entry editing. Since I have school coming up, I decided to release a demo of its current state. Since my summary was getting a bit too long to post in Discord, I decided to write a blog post / newsletter.

Demo download

Windows 64-bit: https://ci.appveyor.com/api/buildjobs/3e0uv6sxov74g50d/artifacts/exotracker-v1.0.60-dev.7z

Source: https://gitlab.com/nyanpasu64/exotracker-cpp/-/tree/timeline-editor (currently commit d5386ea0). It only compiles in recent GCC and Clang (only tested Clang 10), due to using statement expressions.

Demo notes

Timeline system overview

tl;dr skip forward to "Demo feedback" if you want to just play with the program instead of reading documentation.

The frame/order editor is replaced with a timeline editor, and its functionality is changed significantly.

The pattern grid structure from existing trackers is carried over (under the name of timeline rows and grid cells). Each timeline row has its own length which can vary between rows (like OpenMPT, unlike FamiTracker). Each timeline row holds one timeline cell (or grid cell) per channel. However, unlike patterns, timeline cells do not contain events directly, but through several layers of indirection.

A timeline cell can hold zero or more blocks, which carry a start and end time (in integer beats) and a pattern. These blocks have nonzero length, do not overlap in time, occur in increasing time order, and lie between 0 and the timeline cell's length (the last block's end time can take on a special value corresponding to "end of cell")[1].

Each block contains a single pattern, consisting of a list of events and an optional loop duration (in integer beats). The pattern starts playing when absolute time reaches the block's start time, and stops playing when absolute time reaches the block's end time. If the loop duration is set, whenever relative time (within the pattern) reaches the loop duration, playback jumps back to the pattern's begin. A block can cut off a pattern's events early when time reaches the block's end time (either the pattern's initial play or during a loop). However a block cannot start playback partway into a pattern (no plans to add support yet).

Eventually, patterns can be reused in multiple blocks at different times (and possibly different channels).

[1] I'm not sure what to do if a user shrinks a timeline row, which causes an numeric-end block to end past the cell, or an "end of cell" block to have a size ≤ 0, etc.


The timeline system is intended to allow treating the program like FamiStudio or a tracker, with timestamps encoded relative to current pattern/frame begin, and reuse at pattern-level granularity. If you try to enter a note/volume/effect in a region without a block in place, a block is automatically created in the current channel, filling all empty space available (up to an entire grid cell) (not implemented yet).

It is also intended to have a similar degree of flexibility as a DAW like Reaper (fine-grained block splitting and looping). The tradeoff is that because global timestamps are relative to grid cell begin, blocks are not allowed to cross grid cell boundaries (otherwise it would be painful to convert between block/pattern-relative and global timestamps).

Unresolved questions


If you find any crash bugs, let me know. (Some tricky-to-get-right areas were deleting the last row in the timeline, or deleting a long row and the cursor moves into the next, shorter, row.)

If you have any UI or behavior suggestions, tell me too. (I personally think I got the code reasonably watertight, but the UI behavior is a toss-up and I have no clue how people will react.)

You can report issues at https://gitlab.com/nyanpasu64/exotracker-cpp/-/issues.