23

There was a time when computer graphics had to deal with non-square pixels. Happily that time ended once everyone had VGA or better.

But Windows 2 supported both EGA and VGA. And while the latter has resolution 640x480, the best the former can do is 640x350. That's not just fewer pixels overall, it's non-square pixels.

What did Windows do about this?

Provide two complete sets of icons and fonts, one for each aspect ratio?

Design for EGA and accept that everything will look a bit squashed on VGA?

Design for VGA and accept that everything will look a bit elongated on EGA?

Design for halfway in between, and accept that everything will look a little bit distorted on either display?

Something else?

16
  • 13
    There was a time when Windows even supported CGA in all its 640×200 glory! Feb 22, 2023 at 13:36
  • 7
    @StephenKitt And even Hercules Monochrome - Which has somewhat of a luxury crisp and clear look today.
    – tofro
    Feb 22, 2023 at 13:42
  • 7
    @tofro indeed, I mentioned CGA because of its extreme pixel ratio; Hercules produced very nice displays (especially since monochrome displays don’t have a shadow mask). Feb 22, 2023 at 13:45
  • 5
    The standard bitmap fonts (Courier, MS Serif, MS Sans Serif, Small Fonts, Terminal, FixedSys, System) were shipped as part of the graphics driver. The graphics driver supplied these fonts matching the pixel size and aspect ratio to provide a device-independent font display as much as possible. Feb 22, 2023 at 20:06
  • 4
    As an aside, it should be noted that all 16 bit versions of Windows supported EGA, not just Windows 2. (I ran versions up to 3.11 on a machine with an EGA, and the machine was originally supplied with 1.02 which I presume worked, although I admit I never actually tested it).
    – occipita
    Feb 23, 2023 at 13:34

2 Answers 2

38

Most of Windows’ display model is device-independent, or at least provides all the information required to produce consistent displays, and it’s the display drivers that handle discrepancies. As a result, programs look similar regardless of the display’s aspect ratio:

Reversi in 640×200 mode on CGA

Reversi in 640×350 mode on EGA

Reversi in 640×480 mode on VGA

(I’ve scaled these to 4:3, so the images all have the same width and height, but that doesn’t give an accurate representation of how the displays would look on real CGA or EGA monitors.)

When dealing with graphical output, Windows programs use logical coordinates, and those coordinates are mapped to physical coordinates using a configurable mapping. Programs which care about the squareness of squares etc. can request a mapping where logical coordinates correspond to real-world dimensions, e.g. 0.1mm, 0.01mm, 0.01” and so on (although the actual physical result can vary widely, depending on the user’s display adjustments), or even request an “isotropic” mode allowing them to scale their coordinate system as they wish while preserving aspect ratios.

In the screenshots above, note in particular the circles used on the board. The Reversi program only asks Windows to draw circles, and the display driver takes care of actually drawing the circles with whatever horizontal-to-vertical ratio is appropriate. The game board does end up varying in size, because the available display area is different. The CGA and EGA screenshots are of Windows 1.01, with its icon bar at the bottom of the screen; the VGA screenshot is of Windows 2, which gives maximised windows more room (because it eliminated the icon bar, instead allowing icons for minimised windows to appear anywhere on the screen and thus to be covered by windows).

Fonts are provided by display drivers (although they can choose to re-use Windows-provided fonts); if you look at Windows installation disks, you’ll see font files for CGA, EGA, VGA, and possibly 8514/A. This is similar to BIOS support for “plain” text mode (CGA text mode uses 8 vertical pixels per character, EGA uses 14, VGA 16). Many programs use text size as a reference for their general layouts (but users of Windows 3 who tried SVGA modes with the SVGA font probably remember programs which didn’t, and ended up being unusable in that mode; SVGA modes could also be used with VGA fonts, avoiding that problem).

There is one part of the UI that doesn’t adjust: the mouse pointer, which ends up stretched out on EGA and even more so on CGA. Mouse coordinates are always reported as device coordinates.

Icons are device-independent bitmaps, scaled appropriately. In the screenshots above, the icons have approximately the same physical height, even though that requires using a very different number of pixels vertically.

Dialog boxes have a specific coordinate system designed to ensure that their contents remain usable across a variety of outputs (when used properly…).

See the “Introduction to GDI” chapter in Charles Petzold’s Programming Windows for details.

6
  • 3
    If you'd rather demonstrate VGA on Windows 1, I have a patch for that: seasip.info/DOS/Win1/index.html
    – john_e
    Feb 23, 2023 at 9:29
  • 4
    If I understand you right, you're saying that the display driver is programmed with information about the shape of the pixels, and it uses that information to ensure that a square looks like a square on any device that it supports; is that right? The pictures that you've attached seem pretty misleading, since at first glance, they seem to be showing the opposite of what you're actually saying. Feb 23, 2023 at 11:33
  • 2
    @TannerSwett yes, that’s right. Ignore the EGA screenshot (the middle one), it is indeed misleading; the CGA and VGA screenshots show squares which are pretty much squares, and circles which have pretty much the same width and height (calling the CGA circles circles would be rather generous). If you ignored aspect ratio, and drew an 80×80 pixel square, it would be square on a 4:3 VGA output (assuming the user hadn’t adjusted it to no longer be 4:3), occupying 1/8 of the width and 1/6 of the height, but elongated on a 4:3 CGA monitor, occupying 1/8 of the width and 2/5s of the height! Feb 23, 2023 at 13:00
  • 2
    @TannerSwett so instead, on CGA an 80×80 pixel device-independent square would be rendered as an 80×33 on-screen pixel square. Feb 23, 2023 at 13:01
  • 1
    Icon scaling could get a little weird with some applications and displays. My school ran Windows 3.0 on RM Nimbus PCs which have an odd display resolution (retrocomputing.stackexchange.com/questions/5099 suggests 320x250 which sounds about right) which meant it used a very odd icon size (16x32? Not sure) which ended up with some 3rd party applications only displaying half of their icons.
    – occipita
    Feb 23, 2023 at 13:45
0

The standard display device during this time was an analog CRT display. Most of this type of monitor had horizontal/vertical size adjustments that could be used to square things up.

3
  • 1
    Not enough to make up for a program assuming pixels are square, certainly not on CGA, and typically not on EGA either (and even if it were possible, it would result in significant horizontal black bars). Feb 23, 2023 at 15:52
  • 1
    Recommended setup for picture width/height was to obtain a 4:3 picture aspect ratio. You only get square pixels if the pixel/line count also has a 4:3 ratio, as 640x480 on the VGA card does. Feb 23, 2023 at 21:50
  • Most of the programs assume the monitor is adjusted as expected and pixels are non-square, so most programs would look wrong if you tweak the size adjustment to have square pixels.
    – Justme
    Feb 24, 2023 at 9:14

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .