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Re: Graphics issues

From: Eric Wasylishen
Subject: Re: Graphics issues
Date: Mon, 29 Aug 2011 21:17:05 -0600

Hi Andreas,

On 2011-08-29, at 5:08 AM, Andreas Schik wrote:

> Hi there,
> on the weekend, I update GNustep from SVN (trunk) and did a completely
> fresh installation. Since then, I have several graphics issues.
> 1. When using gnustep-art, GWorkspace does not display file icons. I am
> using a viewer in symbol mode. While the navigation control in the upper
> part displayes correctly, no file/directory icons are shown in the lower
> part (symbol view). This does not apply to to gnustep-cairo. Here, the
> correct file type icons are displayed.

This is fixed now. I made a mistake when modifying NSCachedImageRep last week 
(deleted the -draw method when I shouldn't have).

> 2. With both backends, it seems that images which do not have a
> resolution of 72x72 dpi are not displayed correctly. Details:

As far as I know, the current behaviour is correct and matches what Cocoa 
does.. but there may be bugs of course. It's tested somewhat in the GSTest 
Image-test and ImageSelection-test.

> - 72x72 is of course a value that applies to the very notebook I am
> using. Don't know whether this applies to other machines as well.

The GNUstep gui is rendered at 72x72dpi by default, so it applies to all 
machines, and the only way to change that right now is the GSScaleFactor user 
default (e.g. set to 2 for 144x144dpi). We ignore any DPI information from the 
X server.

The only exception is on Windows, where if you increase the system DPI in the 
Windows control panel, GNUstep will respect that. It does that by computing a 
scale factor, so 96 DPI in windows (the default) = 72 DPI in GNUstep.

> - Images are scaled in strange ways. I observed 75x75 dpi images to be
> upscaled in the Y direction only.

Hm, that shouldn't happen.

> There were also images with 90x90 dpi
> being downscaled.

I think that's expected. e.g. a 90x90 pixel image with a DPI of 90x90 would 
have a size of 1x1 inch or 72x72 points, and if the GUI is at the default DPI 
of 72, that maps to 72x72 pixels (so in other words the image is downscaled.)

> - Example is Etoile's MenuServer. While the middle part displays
> correctly, the left and right edges as well as the logo are distorted.
> The middle image is 72x72 dpi the others are 75x75 dpi.

I wasn't able to get MenuServer to work, but I tried drawing the 
EtoileLogo.tiff image in GSTest and it appeared correctly (a bit blurry and 
scaled up because of being 75dpi). So I'm not sure what is going wrong here.

> 3. gnustep-cairo does not handle themes very well. Neos, at least has
> some glitches, e.g. missong knobs on scrollbars. Not a major problem,
> though.
A few images in the Neos theme just need to be set to 72dpi. The scroller knobs 
are actually being drawn, but they're really hard to see because they are 96dpi 
and being downscaled.

Sorry about the trouble created by having images with a DPI != 72 being scaled. 
It's inconvenient but I think it's correct in the long run.

Hope this helps,

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