composer map item content shifts downwards when zoom level greater than 800%

[qgib]

Author Name: Mathieu Pellerin - nIRV (Mathieu Pellerin - nIRV)
Original Redmine Issue: 12151
Affected QGIS version: master
Redmine category:map_composer/printing
Assignee: Martin Dobias

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Since QGIS 2.6, the content of a map item will incrementally shifts downwards as the zoom level increases when starting at 800%. It effectively prevents using an extreme zoom value to fine-tune the location of a composer element (say an arrow item) and the content of a map item.

Steps to reproduce:

1. Open an existing QGIS project
2. Create a composer, or open an existing composer which has a map item
3. Make sure the map item you'll use is set to "cache"
4. Set the composer zoom level to 800%, pan the composer sheet so the map item's content is visible, and hit the map item's "Update preview" button
5. Set the composer zoom level to 825%, and hit the map item's "Update preview" button again
6. You'll notice the map item's content begins to shift downwards
7. Repeat the operation with zoom levels 850%, 875%, 900%, etc. to see the map item's content slowly sicking downwards :)

I'm setting this as a blocker, Nyall, feel free to downgrade if you think it shouldn't be set to such a high priority.

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• 800_percent.jpg (Mathieu Pellerin - nIRV)
• 825_percent.jpg (Mathieu Pellerin - nIRV)
• 875_percent.jpg (Mathieu Pellerin - nIRV)

[qgib]

Author Name: Mathieu Pellerin - nIRV (Mathieu Pellerin - nIRV)

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Adding screenshots that shows the issue; check the rulers to take note of the content shift.

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• 8397 was configured as 875_percent.jpg
• 8396 was configured as 825_percent.jpg
• 8395 was configured as 800_percent.jpg

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• 875_percent.jpg (Mathieu Pellerin - nIRV)
• 825_percent.jpg (Mathieu Pellerin - nIRV)
• 800_percent.jpg (Mathieu Pellerin - nIRV)

[qgib]

Author Name: Martin Dobias (@wonder-sk)

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• assigned_to_id was changed from Nyall Dawson to Martin Dobias

[qgib]

Author Name: Martin Dobias (@wonder-sk)

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Fixed in changeset "70a0a6e3afa3c789866491b5e9ce71a22a874af8".

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• status_id was changed from Open to Closed