Bug 458866

Summary:	Zooming in/out from Fit Zoom to Project jumps to the beginning of the timeline for projects over 300,000 frames long
Product:	[Applications] kdenlive	Reporter:	Karol <krzeszny>
Component:	Timeline & Editing	Assignee:	Jean-Baptiste Mardelle <jb>
Status:	CONFIRMED ---
Severity:	normal	CC:	erjiang
Priority:	NOR
Version First Reported In:	22.08.0
Target Milestone:	---
Platform:	Microsoft Windows
OS:	Microsoft Windows
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Karol 2022-09-08 08:11:13 UTC

SUMMARY
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STEPS TO REPRODUCE
1. Zoom in anywhere in the middle of a project
2. Click "Fit Zoom to Project"
3. Place your cursor somewhere on the timeline
4. Ctrl+mousewheel (on Windows) to zoom in/out at least once

OBSERVED RESULT
Zoom returns to the previous value (before clicking Fit Zoom to Project) but the timeline jumps to the beginning

EXPECTED RESULT
Gradually zooming on the cursor

SOFTWARE/OS VERSIONS
Windows: Version	10.0.19043 Build 19043

ADDITIONAL INFORMATION
The same result happens when you use the zoom slider manually while the cursor isn't on the timeline (it jumps to the beginning.)
Steps to reproduce this side bug:
1. Zoom in anywhere in the middle of a project
2. Move the zoom slider with your mouse or by pressing Ctrl+plus/minus

Comment 1 Karol 2022-09-08 08:40:45 UTC

After some trial and error it turns out this bug only happens in projects longer than 300 thousand frames. 
For example: longer than 166.(6) minutes at 30 fps or longer than 83.(3) minutes at 60 fps

Comment 2 erjiang 2022-09-12 18:12:38 UTC

Confirmed on latest master (e0bee1abf) and additionally noticed that the zoom/scroll bar at the bottom of the timeline disappears after "Fit Zoom to Project"