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Fix invisible scroll bar on light themes - #4845

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confusinguser:bugfix/invisible-scroll-bar
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Fix invisible scroll bar on light themes#4845
confusinguser wants to merge 1 commit into
Kareadita:developfrom
confusinguser:bugfix/invisible-scroll-bar

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@confusinguser

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Fixed

Copilot AI lite review requested due to automatic review settings August 11, 2026 20:25

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Pull request overview

This PR addresses a UI usability issue where the scrollbar becomes effectively invisible when using the Book Reader’s light (“White” and “Paper”) themes, by introducing explicit theme-level scrollbar color variables and applying them in the reader container styling.

Changes:

  • Add --primary-color-scrollbar and --default-state-scrollbar CSS variables to the White theme.
  • Add --primary-color-scrollbar and --default-state-scrollbar CSS variables to the Paper theme.
  • Apply Firefox scrollbar-color styling for the Book Reader scroll container using the scrollbar CSS variables.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File Description
UI/Web/src/app/book-reader/_models/book-white-theme.ts Defines scrollbar CSS variables for the White book-reader theme to ensure contrast on light backgrounds.
UI/Web/src/app/book-reader/_models/book-paper-theme.ts Defines scrollbar CSS variables for the Paper book-reader theme to ensure contrast on light backgrounds.
UI/Web/src/app/book-reader/_components/book-reader/book-reader.component.scss Applies scrollbar-color (Firefox) using the theme-provided variables so scrollbars remain visible.

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Comment on lines 15 to +17
.reader-container {
scrollbar-color: var(--primary-color-scrollbar) transparent;

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As far as I know, there is no way to specify a separate hover color for scrollbars on Firefox, so I chose to use the primary color there as a compromise. Of course, this leads to a small inconsistency, but I think most Firefox-browsers make the scrollbar thin when not hovered, instead of having a separate hover color. Therefore, I think this is the best option

@majora2007

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I need to do some testing with this. I recall one of our users explicitly wanting invisible scrollbars for his eink on white mode. I can't recall if a user theme will allow that or not.

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Scroll bar is invisible with white and paper themes

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