Implement GUI scaling for HighDPI displays and accessibility (SDL2 only)

[falbrechtskirchinger]

This PR implements a global scaling of the window content in the SDL2 driver (a stub has been added to the the WinAPI driver).

The window zoom can be adjusted in the options screen by selecting the desired zoom level from a combo box or by holding down Control and scrolling.

The zoom behavior in the menu screens is a little janky due to how the controls are sized. I've not investigated this any further. After looking at #1579 again, I suspect this is related to RescaleWindowProp/ScaleWindowPropUp. Maybe there's something to be done?

I don't own a HighDPI display myself and have only tested it on setups where windowSize == renderSize. Some optional improvements are under consideration for this PR and are listed in the to-do list below.

Fixes #533
Closes #1579

To-do:

• Actual play testing.
• Dynamically generate the list of window zooms and filter to avoid UI elements becoming inaccessible on small(er) screens.
• Auto-select sensible windowZoom when a HighDPI setup is detected instead of always defaulting to 100%.
• Add tests.
• Maybe add a windowZoom parameter to CreateScreen() to avoid unnecessary calls at the start of the game. (An unnecessary micro-optimization.)
• Split out PointF using alias into a separate PR. There're a few other places that could be updated but are functionally unrelated to this PR. (Done: Add using alias PointF = Point<float> and refactor #1597)
• Split out rounding functions. (Done: Add iround() and round PointF->PointInt by default #1599)
• Refactor based on split-out PRs.
• Investigate RescaleWindowProp/ScaleWindowPropUp. (Current behavior seems fine.)
• Fix soft cursor drifting on zoom change.
• Should the setting be renamed to (G)UI scale and Zoom Game World be removed and always disabled?
• Remove CI commit. (Submit separate PR. CI: Update Boost versions #1596)
• Requires Bump C++ standard version to C++17 #1618, which requires:
  • Bump C++ standard version to C++17 libutil#30
  • Bump C++ standard version to C++17 libsiedler2#24

[falbrechtskirchinger]

I've incorporated @Spikeone's feedback and added an option to decouple scaling the game world from scaling the GUI. On HighDPI setups, some scaling is applied regardless of the setting.

I want to note that I very specifically chose the term "window zoom" (inspired by VSCode) over "GUI scale" because the game world was scaled as well (I wasn't eager to figure out how not to when I started and was far less familiar with the code base than I am now). Unlike in 3D games where scaling is limited to the GUI/HUD and scaling the game world makes no sense due to the perspective projection.

Arguably, this setting could be removed, "Window Zoom" be renamed to "GUI Scale," and the game world scaled depending on DPI, as is the case with the setting turned off.

[Xellzul]

@falbrechtskirchinger
Hey, had quick look at this PR (e64943e) on Windows 11 at 6880x2880 (21:9) resolution:

Everything works as expected except:
Taking in-game screenshots using F12, this was the result with scaling (note the size 1720 x 720 of the screenshot was exact 1/4 of used resolution of 6880x2880 using 400% scaling):

In-game graph was thin

Few screenshots:
https://imgur.com/a/VX9xn1u

[falbrechtskirchinger]

@Xellzul Thank you! I'm away for a few days but should be able to fix those issues over the weekend.

[falbrechtskirchinger]

Both issues should be fixed. As expected, they required minimal changes, though the line drawing could be optimized by calculating the line width only once at a higher level – sacrificing a degree of abstraction – or by implementing BeginDrawLine()/EndDrawLine() functions to calculate and set the width once per multiple draw calls.

iwStatistics could also benefit from a significant rewrite, as many draw positions are specified manually. (In a separate PR and at a later date, of course.)

[falbrechtskirchinger]

• Should the setting be renamed to (G)UI scale and Zoom Game World be removed and always disabled?

I'm making an executive decision and going ahead with the change. "Window Zoom" becomes "GUI Scale" and the DPI scale always scales the game world view. I'm also moving from using unsigned to a new type that encapsulates all the precomputed values and the functions to transform points, obviating some of the additions to `IVideoDriver, as well as further additions or redundant calculations.

[falbrechtskirchinger]

Discovered a few minor things, but otherwise am quite happy with the state of this PR.

[falbrechtskirchinger]

I've started using C++17 features. CI is expected to fail accordingly.

[falbrechtskirchinger]

@Flamefire The rebase is done. Once you approve the changes a force-push should happen automatically within about a minute.
I've added a few more doc comments and applied one of your suggestions to another line.

[Flamefire]

LGTM!

[Flamefire]

Thanks a lot for your effort!

[Blackpearl1]

I just used the newest nightly(e37a322)

I change the GUI zoom to 200% and.... nothing happen.
Restartet the game and... nothing happen.

I Use 3840x2160 (16:9)

Whats wrong?

[falbrechtskirchinger]

I just used the newest nightly(e37a322)

I change the GUI zoom to 200% and.... nothing happen. Restartet the game and... nothing happen.

I Use 3840x2160 (16:9)

Whats wrong?

@Blackpearl1 Changing the GUI scale in the options screen should have an immediate effect.
I need more information:

• What's your OS?
• Are you using the SDL2 video backend/driver? (WinAPI is not supported.)
• Did you get any warning messages when leaving the options screen?
• Could you post screenshots of the options screen with two different GUI scales selected?

The most likely scenario is that you're using the WinAPI backend. If you didn't get a warning message when leaving the options screen, I made some mistake in determining whether the selected GUI scale is supported.

[Blackpearl1]

@falbrechtskirchinger

Are you using the SDL2 video backend/driver? (WinAPI is not supported.)

That was my fault.
I used the win...whatever

I changed it to SDL2 and now it works like a charm. Thank you :D nice job.

The Message that it wont work with the win...whatever comes after changing to SDL2...