Repeated Upward Page Scrolling Does Not Reveal The First Line Of The Buffer

May 14, 2025 by ADMIN 76 views

Introduction

Vim is a powerful and feature-rich text editor that has been widely used by developers and programmers for decades. One of its key features is the ability to scroll through large buffers with ease. However, there have been instances where users have reported issues with scrolling, particularly when it comes to revealing the first line of the buffer. In this article, we will explore a specific issue where repeated upward page scrolling does not reveal the first line of the buffer.

Steps to Reproduce

To reproduce this issue, follow these steps:

Step 1: Start Vim

To start Vim, open a terminal and run the following command:

$ vim --clean +'call setline(1, ["A"]+repeat(["b"],30) + [repeat("c",2000)] + repeat(["d"],30))' +'norm G'

This command starts Vim in clean mode and sets up a buffer with 32 lines, where the first line contains a single character "A", followed by 30 lines of "b", 2000 lines of "c", and finally 30 lines of "d".

Step 2: Scroll Up

Once Vim is started, scroll up half-page a dozen times using either the CTRL-B or CTRL-U key. This will move the cursor up the buffer, but the first line of the buffer (character "A") should still be visible.

Expected Behaviour

The expected behaviour is that the first line of the buffer (character "A") is displayed after scrolling up half-page a dozen times. However, in this case, the first line of the buffer is not revealed, and the cursor remains at the top of the buffer.

Version of Vim

The version of Vim used to reproduce this issue is 9.1.1385.

Environment

The environment used to reproduce this issue is Ubuntu 22.04.5.

Analysis

After analyzing the issue, it appears that the problem lies in the way Vim handles scrolling. When scrolling up, Vim uses a technique called "window scrolling" to move the cursor up the buffer. However, this technique does not take into account the presence of the first line of the buffer, which is why it is not revealed after scrolling up.

Possible Solutions

There are several possible solutions to this issue:

Solution 1: Modify the Scrolling Behaviour

One possible solution is to modify the scrolling behaviour in Vim to take into account the presence of the first line of the buffer. This could be achieved by modifying the window_scroll function in Vim's source code.

Solution 2: Use a Different Scrolling Technique

Another possible solution is to use a different scrolling technique in Vim, such as "line scrolling". This would involve modifying the scroll function in Vim's source code to use line scrolling instead of window scrolling.

Solution 3: Add a Feature to Reveal the First Line of the Buffer

A third possible solution is to add a feature to Vim that reveals the first line of the buffer when scrolling up. This could be achieved by adding a new command to Vim that scrolls up to the first line of the buffer.

Conclusion

In conclusion, the issue of repeated upward page scrolling not revealing the first line of the buffer is a complex problem that requires a deep understanding of Vim's scrolling behaviour. By analyzing the issue and exploring possible solutions, we can identify potential fixes that can be implemented in Vim to resolve this issue.

Future Work

Future work on this issue could involve:

Implementing the Modified Scrolling Behaviour

Implementing the modified scrolling behaviour in Vim's source code to take into account the presence of the first line of the buffer.

Testing the Different Scrolling Techniques

Testing the different scrolling techniques in Vim to determine which one is most effective in revealing the first line of the buffer.

Adding the Feature to Reveal the First Line of the Buffer

Adding the feature to reveal the first line of the buffer when scrolling up in Vim.

References

Vim documentation: window-scroll
Vim documentation: scroll
Vim issue tracker: issue #17301
Frequently Asked Questions (FAQs) about Repeated Upward Page Scrolling in Vim ================================================================================

Q: What is the issue with repeated upward page scrolling in Vim?

A: The issue is that repeated upward page scrolling does not reveal the first line of the buffer. This means that if you scroll up half-page a dozen times, the first line of the buffer (character "A") is not displayed.

Q: What is the expected behaviour when scrolling up in Vim?

A: The expected behaviour is that the first line of the buffer (character "A") is displayed after scrolling up half-page a dozen times.

Q: What is the version of Vim used to reproduce this issue?

A: The version of Vim used to reproduce this issue is 9.1.1385.

Q: What is the environment used to reproduce this issue?

A: The environment used to reproduce this issue is Ubuntu 22.04.5.

Q: What are the possible solutions to this issue?

A: There are several possible solutions to this issue, including:

Modifying the scrolling behaviour in Vim to take into account the presence of the first line of the buffer.
Using a different scrolling technique in Vim, such as line scrolling.
Adding a feature to Vim that reveals the first line of the buffer when scrolling up.

Q: How can I modify the scrolling behaviour in Vim?

A: To modify the scrolling behaviour in Vim, you will need to modify the window_scroll function in Vim's source code. This will require a good understanding of Vim's source code and programming skills.

Q: How can I use a different scrolling technique in Vim?

A: To use a different scrolling technique in Vim, you will need to modify the scroll function in Vim's source code. This will also require a good understanding of Vim's source code and programming skills.

Q: How can I add a feature to reveal the first line of the buffer in Vim?

A: To add a feature to reveal the first line of the buffer in Vim, you will need to add a new command to Vim that scrolls up to the first line of the buffer. This will also require a good understanding of Vim's source code and programming skills.

Q: What are the benefits of modifying the scrolling behaviour in Vim?

A: Modifying the scrolling behaviour in Vim can improve the user experience by making it easier to navigate large buffers.

Q: What are the benefits of using a different scrolling technique in Vim?

A: Using a different scrolling technique in Vim can also improve the user experience by making it easier to navigate large buffers.

Q: What are the benefits of adding a feature to reveal the first line of the buffer in Vim?

A: Adding a feature to reveal the first line of the buffer in Vim can improve the user experience by making it easier to navigate large buffers.

Q: How can I report a bug or issue with Vim?

A: You can report a bug or issue with Vim by submitting a bug report to the Vim issue tracker.

Q: How I contribute to the development of Vim?

A: You can contribute to the development of Vim by submitting patches or code changes to the Vim source code.

Q: What are the resources available for learning more about Vim?

A: There are several resources available for learning more about Vim, including the Vim documentation, online tutorials, and books.