glue-embedded-game-preview

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name: glue-embedded-game-preview description: How the Game tab's live preview embeds and resizes the real running game window, and its zoom/resolution status bar. Triggers: GameHostView, WinformsHost, Runner_MoveWindow, BottomStatusBar, ZoomControl, CurrentDisplayInfoDto, SetParent game window. version: 1.0.0

Glue Embedded Game Preview

The "Game" tab does not render the game into a WPF surface. Glue launches the game as a real, separate process and reparents its native window (SetParent, GameHostView.xaml.cs::EmbedHwnd) into a WinForms Panel hosted by a WindowsFormsHost (GameHostView.xaml → WinformsHost).

Resize flow

WinformsHost_SizeChanged/MainGrid_SizeChanged → SetGameToEmbeddedGameWindow sends a Runner_MoveWindow command — not over the DTO socket, but as a raw _eventCaller/ReactToPluginEvent string handled by CompilerPlugin.HandleEvent (case "Runner_MoveWindow"), which calls Runner.MoveWindow → the real Win32 MoveWindow API directly on gameHandle. Every resize is the real game process's actual OS window changing size/position for real, in-process — there's no visual scaling on Glue's side, and whatever the game's own AspectRatioBehavior/ResizeBehavior (see below) does with that size happens the same as it would for an end user.

WinformsHost and its underlying WinForms Panel (winformsPanel, GameHostView constructor) always stay full-size, filling MainGrid (Stretch, no explicit size/alignment) — even in fixed-size preview mode. Letterboxing is achieved by moving/sizing only the real embedded game window (via Runner_MoveWindow's X/Y/Width/Height) smaller than winformsPanel, whose own dark BackColor (FromArgb(30,30,30), set in the GameHostView constructor) shows through the margins as letterbox bars.

Landmine — do not center by resizing/repositioning WinformsHost/winformsPanel (the ANCESTOR) instead of the game window itself. An earlier version of fixed-size preview did exactly that (WinformsHost.HorizontalAlignment/VerticalAlignment = Center + explicit Width/Height, always passing X=0,Y=0 to Runner_MoveWindow). It looked correct visually but broke rectangle-select and zoom-around-cursor by exactly the centering offset: gameHandle's position relative to its own immediate parent (winformsPanel) never changed, so it never received a native move notification — only its ancestor moved. MonoGame/SDL's cached window position (used to translate the cursor's absolute screen position into client-relative mouse coordinates) went stale by that offset. The fix was to always keep winformsPanel full-size/unmoved and instead pass the letterbox offset as Runner_MoveWindow's X/Y — since that's a real position change to gameHandle relative to its own immediate parent, it generates the native move notification MonoGame/SDL needs.

Landmine — "connected" does not mean the game can handle a DTO yet

Runner_GameStarted fires as soon as the game process has a MainWindowHandle (Runner.cs), which is earlier than the game being able to act on anything. In generated Game1.Initialize, GameConnectionManager is constructed (and connects) several statements before GlueControlManager, with CameraSetup.SetupCamera between them. In that window the socket is live but GlueControlManager.Self is null, so nothing can dispatch an incoming DTO. Anything sent on game startup therefore needs a retry budget that outlasts graphics-device setup, not just the connection (BorderlessRetryPolicy). Waiting on GameCommunication_Connected does not close this — connected is precisely the state where it fails.

Retry on Succeeded, never on the reply's content. The game answers that window with GameConnectionManager.NotReadyPayload and Glue turns it into an unsuccessful GeneralResponse, so Succeeded is the readiness signal. Most HandleDto overloads return void — SetBorderlessDto included — and a healthy game answers those with an empty payload, so a "did it send anything back?" check never becomes true no matter how long the budget is.

Zoom / resolution status bar

BottomStatusBar.xaml (ZoomControl + resolution TextBlock) is fed by CurrentDisplayInfoDto, pushed from GlueControl.Editing.CameraLogic (Embedded/Editing/CameraLogic.cs, game process only — PushZoomLevelToEditor) and applied on the Glue side in CommandReceiving/CommandReceiver.cs::HandleDto(CurrentDisplayInfoDto), which writes CompilerViewModel.CurrentZoomLevelDisplay/ResolutionDisplayText. Zoom itself (ChangeZoomDto, +/-) is a separate concept from window size — it scales Camera.Main.OrthogonalHeight inside the game and is independent of what size the embedded OS window actually is. None of this zoom state is persisted to the project file; it resets every Glue launch.

Landmine — GameCommunicationPlugin.csproj has no implicit globbing

<EnableDefaultCompileItems>false</EnableDefaultCompileItems> means a new .cs file under this project (e.g. adding a class next to GameHostView.xaml.cs) silently compiles into nothing until it's added to the <Compile Include="GlueControl\Views\... <ItemGroup> by hand - no error, the type just doesn't exist for anything that references the assembly (CS0103 in a consumer, not in this project).

Project's target resolution vs. live preview size

The project's configured target resolution/aspect ratio lives in DisplaySettingsViewModel/GlueCommon/SaveClasses/DisplaySettings.cs (Glue/Plugins/EmbeddedPlugins/CameraPlugin/) — edited via the Camera Settings panel (CameraSettingsControl.xaml) — and normally only takes effect through codegen (CameraSetupCodeGenerator.cs) for what a built game does at startup/on resize. By default the live preview's WinformsHost panel ignores it and always stretches to fill the tab.

The "fixed-size preview" toggle (BottomStatusBar's aspect-ratio icon, CompilerViewModel.IsFixedSizePreview, issue #2035) is the one exception: when on, GameHostView.SetGameToEmbeddedGameWindow sizes/centers the real embedded game window (not WinformsHost — see the resize-flow landmine above) to DisplaySettings.ResolutionWidth/Height scaled to fit the panel (FixedSizePreviewCalculator, unit-tested). Landmine: "100%" there is not the raw resolution — it's ResolutionWidth/Height * DisplaySettings.Scale / 100 (FixedSizePreviewCalculator.GetEffectiveTargetResolution), since Scale (Camera Settings' desktop scale, e.g. 400%) is how a real launched window is already upscaled from the project's internal resolution. Using the raw resolution previews the wrong size for any project with a non-100% Scale.

Landmine — editor zoom "100%" is not the same "100%" as a real launch

CameraLogic's own zoom (+/-, zoomLevels) is an editor-only pan/zoom convenience: its 100% means "1 world unit = 1 window pixel," computed purely from Camera.Main.DestinationRectangle.Height (UpdateCameraToZoomLevel) — it has no idea what Data.Scale is. The real generated game (CameraSetupCodeGenerator.cs ~line 696) instead sets Camera.Main.OrthogonalHeight = DestinationRectangle.Height / (Data.Scale / 100), which — at the window's natural size (ResolutionHeight * Scale / 100 pixels tall) — always works out to OrthogonalHeight == ResolutionHeight, independent of Scale. Scale is a pure pixel-multiplier (crisp upscaling), not a "show more/less world" zoom.

Fixed-size preview mode locks onto that value, not editor-zoom-100%: CameraLogic.SetFixedSizePreviewLock pins OrthogonalHeight to a constant (DisplaySettings.ResolutionHeight, sent via SetFixedSizePreviewLockDto) regardless of the embedded window's current pixel size — so when the Glue panel is too small and the window gets letterbox-shrunk (FixedSizePreviewCalculator), the whole picture optically shrinks uniformly (screenshot-thumbnail style) instead of revealing more world, which is what using editor-zoom-100% would have done. DoZoomPlus/DoZoomMinus (mouse wheel, Ctrl+/- hotkeys, and the Glue UI's ChangeZoomDto all route through these two) no-op while locked. The lock is re-sent whenever ResolutionChanged fires (MainCompilerPlugin) but not ScaleChanged — Scale only affects window pixel size (SetGameToEmbeddedGameWindow), never the locked OrthogonalHeight target.

Landmine — editor zoom % ratio does match Data.Scale; don't assign OrthogonalHeight an absolute value

DestinationRectangle.Height / OrthogonalHeight is panel-size-invariant and equals Data.Scale/100 at the matching zoom level — only an absolute OrthogonalHeight assignment (vs. the divisor formula) breaks that. See UpdateCameraToZoomLevel's forceToGameDefault (issue #2044).