Differential D7973

Make QPainter canvas render at device pixel size in hidpi mode
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Authored by alvinhochun on Sep 24 2017, 5:21 PM.

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Reviewers

rempt

Group Reviewers

Krita

Maniphest Tasks

T2299: Make the canvas behave in HiDPI mode
T5257: HiDPI canvas bugs

Summary

Before this change, the QPainter-based canvas will render in the "logical pixel" size, e.g. zoomed in 200% when dpi scale factor is 2x, which causes the canvas to render all blurry.

After this change, the QPainter-based canvas will render in the device pixel size. This does not change the existing view scaling, which means with a dpi scale factor of 2x, setting a scale level of 50% will result in a pixel-perfect canvas render, while 100% will be effectively 200%.

I would assume this works on Linux, but somebody should test this on OS X with a retina display...

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R37 Krita

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alvinhochun created this revision.Sep 24 2017, 5:21 PM

alvinhochun added tasks: T5257: HiDPI canvas bugs, T2299: Make the canvas behave in HiDPI mode.

I'm not sure I see any difference on OSX:

With the patch:

Withouth the patch:

But I'm notorious in not seeing these kind of things. The patch itself looks fine to me.

This revision is now accepted and ready to land.Sep 25 2017, 8:51 AM

Oh, I should've made some test images with 1-pixel-wide lines. Best to test at 50% zoom (assuming the mac uses 200% dpi scaling), and also test some random scale levels below 50% and within 50~100%.

Surely you shouldn't see any difference at 100% zoom...

Ok, here are three images for testing pixel-perfect rendering:

With these images the change should be pretty obvious at <100% and higher non-integral zoom levels. Here's what I get at 50% zoom, at scale factor 200% (view at original resolution):

@rempt Can you please test again with these images at 50% zoom and other non-integral zoom levels?

Here are six screenshots at 50%: I can do at another zoom level, but not right now. Dinner time...

alvinhochun mentioned this in D7982: Fix OpenGL canvas scaling algorithm in hidpi mode.Sep 25 2017, 4:36 PM

Hi, @alvinhochun!

Could you test if this test works fine on QPainter canvas?

https://phabricator.kde.org/D7982#148929

In D7973#148930, @dkazakov wrote:

Hi, @alvinhochun!

Could you test if this test works fine on QPainter canvas?

https://phabricator.kde.org/D7982#148929

No, it works the same way as the OpenGL canvas, but it's not a regression.

One thing I should also test is moving the Krita window between two monitors of different dpi scaling settings (Windows 10)...

alvinhochun added a dependent revision: D8044: Remove manual double buffering in QPainter canvas.Sep 28 2017, 8:16 PM

alvinhochun mentioned this in D8044: Remove manual double buffering in QPainter canvas.Sep 29 2017, 9:02 AM

Updated diff so it applies after D8044

rempt accepted this revision.Oct 2 2017, 8:25 AM

This revision is now accepted and ready to land.Oct 2 2017, 8:25 AM

alvinhochun mentioned this in T7130: Modify code that uses mouse coordinates to work in device pixel space under high DPI mode.Oct 3 2017, 10:59 AM

alvinhochun abandoned this revision.Oct 4 2017, 3:16 PM

alvinhochun mentioned this in T2299: Make the canvas behave in HiDPI mode.

Revision Contents
Changeset List

			Path	Packages
M			libs/ui/canvas/kis_image_patch.h (2 lines)
M			libs/ui/canvas/kis_image_patch.cpp (5 lines)
M			libs/ui/canvas/kis_prescaled_projection.h (2 lines)
M			libs/ui/canvas/kis_prescaled_projection.cpp (27 lines)
M			libs/ui/canvas/kis_qpainter_canvas.cpp (5 lines)

	Status	Author	Revision
	Closed	alvinhochun	D8044 Remove manual double buffering in QPainter canvas
	Abandoned	alvinhochun	D7973 Make QPainter canvas render at device pixel size in hidpi mode