Fullscreen spans all monitors when capturing All Displays

[ozy24]

Summary

Makes Fullscreen (Ctrl+Shift+G) span the entire virtual desktop (all monitors) when capturing All Displays, instead of only the nearest monitor.

Motivation

ShaderGlass already captures every connected monitor via the existing "All Displays" input (NULL HMONITOR), and applies the correct virtual-screen offset for Glass alignment. The only gap was Fullscreen: ToggleBorderless used MonitorFromWindow and so only ever covered one monitor, leaving no way to span the overlay across all displays.

What changed

• ToggleBorderless — when "All Displays" is the active capture (capture API, no window, NULL monitor, not image/device), sizes the borderless window to SM_XVIRTUALSCREEN / SM_YVIRTUALSCREEN / SM_CXVIRTUALSCREEN / SM_CYVIRTUALSCREEN. All other capture modes are unchanged (still nearest monitor).
• SaveProfile — persists the "All Displays" selection by writing CaptureDesktop "All Displays" for the NULL-monitor case. LoadProfile already matches that name, so the selection (and its menu checkmark) is restored on load instead of falling through to nothing selected. Only applies on Win10 2004+/Win11 where the NULL-monitor entry exists; never for image/device/window captures.
• MANUAL.html — one-line note documenting the behaviour.

How to use

1. Input → Desktop → All Displays
2. Start capture (Glass mode)
3. Fullscreen / Ctrl+Shift+G to span all monitors

Single-monitor, window, and file capture behaviour is unchanged.

[mausimus]

Interesting, I guess it doesn't say that in Microsoft's docs so AI couldn't know but you can pass NULL HMONITOR and that will capture all desktops (it's already what ShaderGlass defaults to). So to handle multi-monitor output all that's needed is to make the window span all screens (you can kinda resize it manually even now but can't make fully borderless).

[ozy24]

Thanks for the feedback @mausimus!

Reworked as you suggested. Dropped the multi-monitor compositor - "All Displays" (NULL HMONITOR) already captures every screen and ShaderGlass::Initialize already applies the virtual-screen offset, so the only change needed was making Fullscreen span all monitors.

Now a single commit: when "All Displays" is active, ToggleBorderless sizes to SM_X/Y/CX/CYVIRTUALSCREEN; otherwise unchanged. Down to ShaderWindow.cpp + a one-line MANUAL.html note. Builds clean on Release|x64.

[mausimus]

Ok I tried it and it does work, some people have indeed asked for this feature. The issues I have are:

• it should not be the default; with multi monitor setups I think you normally fullscreen something on one monitor and want to ShaderGlass fullscreen on top of just that; most shaders are also built for single display (bezels etc.)
• this feature should be for advanced users only hidden behind a checkbox in the Output menu "Fullscreen on All Displays" (placed after the existing Fullscreen menu item); only if someone ticks it then they would get new behavior when entering fullscreen

[ozy24]

Hello, yes, that makes sense. My use case is slightly different from most Shaderglass users, as I use particular shaders to reduce eye strain, where multi-display spanning makes more sense. I'll get the PR updated accordingly.

[ozy24]

Hello,

I've updated the PR.

What changed

• Fullscreen no longer spans all monitors by default. The default behavior is unchanged: fullscreen still covers only the monitor nearest the ShaderGlass window.
• Added an opt-in checkbox in the Output menu: Fullscreen on All Displays, placed directly after Fullscreen.
• The checkbox is off by default and is persisted in settings, so it stays as you left it across restarts.
• When the checkbox is ticked and you enter fullscreen, ShaderGlass spans the entire virtual desktop — but only if All Displays is also selected as the desktop input. That way every monitor has actual captured content; otherwise the extra monitors would just show black.
• With any other input (single monitor, window, file, etc.), fullscreen still covers a single monitor, even if the checkbox is ticked.

How to use it

Input → Desktop → All Displays
Output → tick Fullscreen on All Displays
Fullscreen (Ctrl+Shift+G)
To stick after restart, save as default profile while All Displays is selected.

Happy to adjust anything if you'd like it handled differently.