Re: [platform-swt-dev] Correct Implementation for HiDPI

[Tom Schindl <tom.schindl@xxxxxxxxxxxxxxx>]

Yes the GC implementation simply multiplies the value it gets.

A problem with that approach although is that if you draw at the outline
of a canvas half of your line is drawn outside.

The only possibility to fix that is that you apply a transform because
everything is multiplied by eg 2.0 you can't offset the line 1px, this
leads to the problem that you can't stroke a rectangle but need to do
that line by line (top-line offset down, right line offet left, bottom
line offet top, left line offset right).

While HiDPI works very well on OS-X we have had major problems on Win32.

Tom

On 15.05.18 11:35, Sravan K Lakkimsetti wrote:
> Hi,
> 
> SWT scales automatically on Windows and Linux. Application won't have
> access to the screen coordinates. SWT does call a callback to the
> application for a new image when required (SWT supplies scale factor
> when it requests). If you use imageproviders(or imagedescriptor) you'll
> get sharper images otherwise the images and drawing gets scaled
> automatically will result in slightly blurred images.
> 
> Thanks and Regards,
> Sravan
> 
> Sravan Kumar Lakkimsetti
> IBM India Pvt Ltd,
> Embassy Golf Links Business Park, D Block,
> Off Indiranagar-Kormangla Inner Ring Road,
> Bangalore - 560071, India
> Phone: 91-80-41776858
> 
> -----Original Message-----
> From: Thomas Singer [mailto:ts-swt@xxxxxxxxxxx]
> Sent: Tuesday, May 15, 2018 2:28 PM
> To: platform-swt-dev@xxxxxxxxxxx
> Subject: Re: [platform-swt-dev] Correct Implementation for HiDPI
> 
> According to my understanding on macOS the zooming is handled
> transparently - for the application it looks like it does not have to
> perform any scaling itself, images are drawn scaled automatically by
> macOS and all paint operations are scaled automatically, too, with an
> unscaled coordinate-system. Is this right?
> 
> If using SWT as designed now, should SWT scale automatically, too, on
> Windows and Linux. Or is the application able to (and has to) access the
> full screen coordinates, thus painting each pixel even at 200% zoom?
> 
> --
> Best regards,
> Thomas Singer
> =============
> syntevo GmbH
> https://www.syntevo.com
> https://www.syntevo.com/blog
> 
> 
> On 2018-05-03 16:50, Thomas Singer wrote:
>> Hi all,
>>
>> For our application SmartGit (et al) we are using HiDPI support since
>> it first was supported in SWT by adding workarounds where necessary.
>> In the mean-time the SWT-API has changed significantly in this area
>> and I only adapted our SWT use to get it working. Though I have the
>> feeling we are not using it as designed according to the current API,
>> especially on Linux the HiDPI detection does not work reliable for us.
>>
>> Is there a documentation how to implement image handling and paint
>> operations correctly on HiDPI screens (we are just supporting 100% and
>> 200% zoom level)? Thanks in advance.
>>
>> --
>> Best regards,
>> Thomas Singer
>> =============
>> syntevo GmbH
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