Fix: 'Cache' top and bottom lines of textfile viewer to avoid overdraw. #9131
+70
−27
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The text file viewer calculated the number of lines required to set the scrollbar, but did not retain this information, so this was recalculated on every draw operation. This includes overdrawing text outside the bounds of the current scroll position. With this change the top and bottom lines for each line of text are remembered, and reflowing is avoided where possible. Text outside the current scroll bounds is not drawn. Additionally the scroll interval is now based on text lines instead of pixel lines, which increases the text capacity depending on the font size.
Text files with more than 64k wrapped lines would exceed the scrollbar capacity and cause an assert. This is harder to reach now that the scrollbar counts lines instead of pixels.
PeterN
force-pushed
the
textfile-cache-reflow
branch
from
e231434 to
0981ec6
Compare
rubidium42
approved these changes
Apr 29, 2021
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Motivation / Problem
The text file viewer calculated the number of lines required to set the scrollbar, but did not retain this information, so this was recalculated on every draw operation. This includes overdrawing text outside the bounds of the current scroll position.
This is a considerable performance drag, although possibly only really noticeable with a debug build. For me a large file took over a second for each redraw.
Description
With this change the top and bottom lines for each line of text are remembered, and reflowing is avoided where possible. Text outside the current scroll bounds is not drawn.
Additionally the scroll interval is now based on text lines instead of pixel lines, which increases the text capacity depending on the font size.
Limitations
This most likely stomps all over #7786, however this is a more specific change and smaller in scope. What this does is also very similar to parts of that change.
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.