GIMP Undo History depth limit not configurable via Preferences

Question

GIMP utilizes an in-memory undo stack that captures image modifications as discrete snapshots. While the Undo History panel displays the current depth of this stack, there is no graphical interface within the Preferences dialog to adjust the maximum number of steps allowed.

The default limit is typically set to 20 steps, and older snapshots are discarded in a first-in-first-out manner once the threshold is reached. Although this value can be modified via manual configuration file edits or the --max-undo-steps command-line argument, these methods remain outside the core UI functionality.

Is there a roadmap for integrating the undo stack depth configuration directly into the GUI in future releases? How does the application handle memory pressure when the step limit is set significantly beyond the default via external configuration files?

Tasadduq Burney · Answer

Undo Depth Configuration in GIMP
There is currently no roadmap or scheduled release that integrates the undo stack depth configuration into the GIMP graphical user interface (GUI). As of GIMP 2.10.x and the 2.99/3.0 development branches, this setting remains excluded from the Preferences dialog.

External Configuration Methods
Because the GUI lacks this control, you must use one of the following two methods to modify the default limit of 20 steps:

Command-Line Argument: Launch the application using the following flag to set a session-specific limit:
    gimp --max-undo-steps 50
  
  Configuration File: Edit the gimprc file (typically located in ~/.config/GIMP/2.10/ on Linux or the equivalent AppData folder on Windows). Locate or add the following line:
    (max-undo-steps 50)

Note: GIMP must be restarted for changes in the gimprc file to take effect.

Memory Pressure and Resource Handling
GIMP handles undo steps by capturing image snapshots. When you increase the step limit beyond the default via external configuration, the application manages memory as follows:

Linear Growth: Memory consumption generally grows linearly with the number of undo steps. Each additional step requires additional image buffers to store the state of the canvas.
  RAM Exhaustion: If the undo limit is set significantly high, GIMP may consume all available physical RAM. This typically leads to system swapping (disk paging), which severely degrades performance.
  Termination: In extreme cases where the system cannot provide the requested memory, the application may crash or be terminated by the operating system's Out-Of-Memory (OOM) killer.

Verification Steps
To verify your new limit is active, perform the following:

Launch GIMP using one of the methods above.
  Open an image and perform a number of edits exceeding your new limit (e.g., 55 edits for a limit of 50).
  Open the Undo History panel; confirm that only the most recent 50 steps are retained and the oldest are discarded.

To provide a more specific memory recommendation, please specify your total available system RAM and the average resolution of the images you are processing.

GIMP Undo History depth limit not configurable via Preferences

1 answer

Undo Depth Configuration in GIMP

External Configuration Methods

Memory Pressure and Resource Handling

Verification Steps

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