[PATCH] Add support for Hi-DPI displays

[julian37]

It would be nice if 0 A.D. could take advantage of Hi-DPI displays, such as Apple's Retina displays.

As far as I can tell, this requires the following:

• Upgrading to SDL2, which adds the SDL_WINDOW_ALLOW_HIGHDPI flag
• Ensuring the GUI remains at the original size (i.e. magnifying it by 2x with respect to 3D graphics)

And the following are nice-to-haves:

• Doubling the resolution of the prerendered fonts for crisp text rendering
• Providing all bitmap graphics in double the resolution (seeing that 4K displays are on the horizon, perhaps new bitmaps graphics should be prepared at 4x the resolution)

I've attached a simple-minded patch for the first issue (SDL2 support) to ticket #2041, and I've prepared a patch to address issues 2 and 3 (scaled-up GUI and high-res fonts), will attach it shortly.

[historic_bruno]

SDL2 support has been merged into SVN. It's not yet the default for OS X, but will be for A17 and this task can be worked on.

[historic_bruno]

r16223 added a GUI scaling option.

[historic_bruno]

patch by orangy from #3692

[historic_bruno]

#3692 was a duplicate, I moved the patch here.

[Itms]

Move tickets from the review queue to the rfc one.

[Moul]

I am using a HiDPI screen almost 4K and 13': It not very good to play with it. Here a screenshot with current SVN version a21: ​http://pix.toile-libre.org/upload/original/1473526126.png

[fabio]

Hi, to scale the GUI see ​here.

[Vladislav Belov]

Too few time remaining for A21 release.

[wraitii]

Attached patch is rebased, fixed, and I added a config flag to enable/disable it. The problem is that high DPI is excruciatingly slow on my system, and I suspect it would be similar or many other people.

It would be great if the renderer could have a resolution independent from the screen/GUI resolution, i.e. render the GUI at retina resolution and then renderer at non-retina, but that would require us to decouple the renderer resolution and it's not that easy and probably requires using frame buffers all the time and I don't believe we want to support that now.

[elexis]

Moving to the new WIP milestone.

[Stan]

Use c++ casts as c casts are not tested on compile time.

[Stan]

Add back the default.cfg changes.

[wraitii]

​https://code.wildfiregames.com/D1925

[Langbart]

duplicate ticket closed #6726