5.3 Display

Scale. View > Scale 1x/2x/3x, or press F2 to cycle. Scaling is always a whole number of pixels, so the picture stays sharp.

Fullscreen. F11, or View > Fullscreen. The image is centred with black bars, keeping the correct shape. F11 again returns. (Esc will not: it is the Break key.) On a Mac, macOS takes F11 for Show Desktop: use Control+Command+F (⌃⌘F), the green button in the title bar, or View > Fullscreen.

CRT effect. One choice, in View or Settings > Preferences: off, Scanlines, Soft scanlines, TV or PC monitor. Choosing one switches the others off, and unchecking it turns the effect off.

• Scanlines overlays soft scanlines, for a more period-accurate look.
• Soft scanlines (View > CRT Soft Scanlines) draws the same idea on the GPU: softer, slightly blurred lines than Scanlines. It needs a graphics card with OpenGL; on a computer without one (software OpenGL) it costs much more processor time than Scanlines, which is why it is a separate choice.
• TV draws the display through a GPU emulation of a cathode-ray tube: a curved screen (the whole picture stays inside the glass, with a thin black margin), bloom around bright areas, scanlines and a phosphor mask.
• PC monitor is the same, flatter.

The same frame in each mode, off, Scanlines and Soft scanlines above, TV and PC monitor below, on the NextZXOS welcome screen.

It is off by default. Scanlines is a simple overlay drawn by jnext itself, on any computer and at no extra cost. While the effect is off nothing extra is created or drawn. If a GPU look cannot run on this computer, jnext says so and carries on with the normal display (with the software Scanlines, if Soft scanlines was the choice; a saved choice is tried again at the next start). The Soft scanlines, TV and PC monitor entries are absent from builds made without GPU support.

Layers. The Next composites several video layers — the classic ULA screen, Layer 2, the tilemap and up to 128 sprites — and the running program decides their stacking order and transparency. There is nothing to configure; it is simply what you see.

You can, however, pull them apart, which is useful when something looks wrong and you want to know which layer is responsible:

jnext --headless demo.nex --delayed-screenshot l2.png \
    --delayed-screenshot-layers layer2 \
    --delayed-screenshot-frames 200 --delayed-automatic-exit-frames 250

The same frame with only Layer 2, and with only the sprites. Excluded layers are treated as switched off, so what remains still composites normally. Leaving out ula also removes the border, since that is the ULA's job.

Screenshots. File > Save Screenshot… (Alt+S) or the toolbar Screenshot button asks for a name and writes the file. JNEXT remembers the directory. For scripted, repeatable captures, see chapter 7.

Quick screenshots. When you want a sequence of captures, the dialog is the slow part. File > Quick Screenshot (Alt+K) writes immediately, with no dialog at all: the file is named after the date and time (jnext-20260718-103412.png) and lands in the quick-screenshot directory, which the status bar names each time so a capture is never lost. Two captures in the same second get -02, -03 and so on rather than overwriting each other. The directory (by default ~/.jnext/screenshots, created on first use) and the format are set under Settings > Preferences > Paths.

Two formats, chosen by the extension. There is no format option anywhere; the name you give decides.

• .png is the picture — every layer, the border, the palette, exactly as the window shows it. A 640x256 frame is written as a 640x512 file so the pixels are square.
• .scr is the classic ZX screen dump that Spectrum graphics tools read and write: a copy of the ULA screen memory as it stands, taken from whichever screen bank is on display. Nothing is converted, so the bytes are exactly what the program put there.

.scr has a real limit, and it is worth knowing before you rely on it: the format can only describe the classic ULA screen. Layer 2, the tilemap, the sprites, the LoRes modes and the Next palettes have no place in it and are simply not in the file — capture a Layer 2 game as .scr and you get whatever happens to be left in the ULA screen memory, which is often nothing. Use .png for those.

In the Timex hi-colour and hi-res modes the file is 12288 bytes instead of the usual 6912: those modes use two screen planes and both are written, which is what Timex-aware tools expect. The file does not record which of the two modes produced it, because the format has nowhere to say so.

The same choice applies on the command line:

jnext --headless demo.nex --delayed-screenshot shot.scr \
    --delayed-screenshot-frames 200 --delayed-automatic-exit-frames 250

--delayed-screenshot-layers is refused with a .scr, since a screen dump has no layers to choose between.

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