Image jumps unexpectedly when selection dragging against a window edge

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Anibina
Posts: 22
Joined: Fri Apr 26, 2019 7:53 am

Image jumps unexpectedly when selection dragging against a window edge

Post by Anibina »

XnView MP Windows
Version 1.0 64bits (Apr 28 2022)


Dragging a selection against a window edge, in a specific order, causes the image to jump unexpectedly.


Effect: Image moves unexpectedly

To reproduce:
1. Open an image, large enough so that parts of it end up outside the window when it's zoomed in
2. Zoom in to the middle of the image
3. Move the mouse pointer near the window's left edge
4. Hold down the left mouse button to start drawing a selection
5. Move the mouse pointer to the right of the window's right edge, to move the image to the left,
6. Keep moving the mouse pointer slightly outside the window's right edge, until the selection's left edge is outside the window's left edge.
6. Move the mouse pointer to the left of the window's left edge, to move the image to the right, until the selection's left edge scrolls into view.


Actual behaviour (bug): :bug:
The image jumps an unexpected amount.

The selection appears on the right half of the XnView MP window, for a split second.

Then the selections right edge appears in the middle of the window, and the selections left edge is at the window's left edge at the mouse pointer.

This same unexpected issue is also observed when the selection's top edge is scrolled above the window, then scrolled back slowly.

xnview_mp_image_jumps_when_dragging_selection_against_window_edge.mp4

Here's the part with the unexpected jump, in slow motion.

xnview_mp_image_jumps_when_dragging_selection_against_window_edge_slow_motion.mp4
Expected behaviour:
The selection's left edge should scroll into view slowly. Without the image and selection jumping unexpectedly.

The expected behavior is observed when the selection is started near the window's right edge.

And the selection is dragged outside the window's left edge, until the selection's right edge moves outside the window's right edge.

Then, the selection is dragged outside the window's right edge, until the selection's right edge scrolls into view.

Now the selection's right edge scrolls into view slowly.


This expected behavior is also observed when the selection is drawn near the window's bottom edge.

And the selection's bottom edge is first scrolled below the window's bottom edge, then back into view.

xnview_mp_image_doesnt_jump_when_dragging_selection_against_window_edge.mp4
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