GitAuto: Panning Vertically

[gitauto-ai]

Resolves #935

Why is this feature needed?

The current reader behavior in landscape mode when zoomed in does not properly support vertical panning. Users expect that tapping right or left will first attempt to pan up or down (depending on which edge of the page is visible) before moving to the next or previous page. This update aims to improve the user experience by enabling more intuitive navigation when the page is zoomed in.

What and how are we changing? Why this approach?

We modified the logic in PagerViewer to check for vertical panning before falling back to the horizontal page navigation. When a user taps right, the code now checks if it can pan down (instead of immediately panning right) using the holder.canPanDown() function. Similarly, when a user taps left, it checks if it can pan up before executing a pan left. This approach ensures that if there is spillover for vertical navigation, the reader will pan accordingly, and if the edge of the page is reached, it will then trigger the page change.

What actions are required from users?

No immediate actions are required from users. However, it is recommended to update to the latest version of the app to benefit from this enhanced panning behavior in landscape mode when zoomed in.

How does it work? (Technical details)

• In PagerViewer.kt:

• For the right tap event, the app now calls holder.canPanDown() to decide whether to pan vertically (down) or if not possible, then fall back to the existing behavior of panRight().
• For the left tap event, the app similarly uses holder.canPanUp() before calling panLeft().
  • These changes rely on the underlying capabilities of the page holder (canPanDown, panDown, canPanUp, panUp) to determine and execute the correct panning behavior.

Is it backwards compatible?

Yes, the change is backwards compatible. If the vertical panning conditions are not met, the application will utilize the existing horizontal pan behavior. Users who have not updated their reading patterns or whose pages do not have vertical panning capability will not notice any change in behavior.

Any other considerations?

We considered other approaches such as dynamically adjusting the pan behavior based on the zoom level or user settings; however, checking for the capability directly on the page holder and conditionally executing the appropriate pan provided the cleanest and most maintainable solution. Further testing will be necessary to ensure seamless performance across different page types and zoom levels.

git fetch origin
git checkout gitauto/issue-935-20250530-031454-hPbW
git pull origin gitauto/issue-935-20250530-031454-hPbW

[sourcery-ai]

Reviewer's Guide

Enhanced the pager navigation logic to attempt vertical panning (down/up) before default horizontal panning when the ‘navigateToPan’ config is enabled.

Updated Class Diagram for PagerViewer

classDiagram
    class PagerViewer {
        +moveToNext()
        +moveToPrevious()
    }

Loading

File-Level Changes

Change	Details	Files
Forward navigation now tries vertical panning down before panning right.	Wrapped holder.panRight() call in a canPanDown() check Invoke holder.panDown() if vertical movement is possible Fallback to holder.panRight() when downward pan isn’t available	app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerViewer.kt
Backward navigation now tries vertical panning up before panning left.	Wrapped holder.panLeft() call in a canPanUp() check Invoke holder.panUp() if upward movement is possible Fallback to holder.panLeft() when upward pan isn’t available	app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerViewer.kt

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#935	Enable vertical panning when zoomed in landscape mode, so that tapping right/left moves the page up/down to fit the whole page in the screen.	✅
#935	When the page reaches the top/bottom while zoomed in, tapping right/left should navigate to the next/previous page.	✅

Possibly linked issues

• Panning Vertically #935: The PR adds checks for vertical panning before allowing horizontal page changes, resolving the issue.

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