fix(LuaRenderer): visible pink alpha mask on platforms without LWA_COLORKEY support

[Aurumaker72]

Changes LuaRenderer and GDIPresenter to use UpdateLayeredWindow with ULW_COLORKEY instead of relying on the DWM compositing a window with LWA_COLORKEY properly.

Closes #243.

[Copilot]

Pull request overview

Addresses issue #243 by changing how the Lua overlay layers are composited, aiming to prevent the magenta/pink colorkey mask from becoming visible on platforms where LWA_COLORKEY is unreliable/unsupported.

Changes:

• Removes the GDI “front DC” path and WM_PAINT-based GDI overlay presentation.
• Consolidates the overlay window classes into a single lua_overlay class.
• Presents GDI overlay content via UpdateLayeredWindow(..., ULW_COLORKEY) from the render loop.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/Views.Win32/lua/LuaTypes.h	Removes gdi_front_dc from the Lua rendering context since the GDI overlay is no longer blitted via WM_PAINT.
src/Views.Win32/lua/LuaRenderer.cpp	Reworks overlay window creation/registration and switches GDI overlay presentation to UpdateLayeredWindow colorkey updates.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

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[Copilot]

GDIPresenter::init() allocates a new compatible bitmap but never initializes it. Because end_present() now uses UpdateLayeredWindow(..., ULW_COLORKEY), any pixels that aren’t explicitly drawn/cleared can show up as garbage or as an opaque overlay. Initialize the back DC to the mask color right after creating/selecting m_gdi_bmp (same approach as in resize()).

Suggested change

	// Initialize the back-buffer bitmap to the mask color to avoid garbage pixels
	RECT init_rect = {0, 0, (LONG)m_size.width, (LONG)m_size.height};
	const auto init_brush = CreateSolidBrush(m_mask_color);
	FillRect(m_gdi_back_dc, &init_rect, init_brush);
	DeleteObject(init_brush);

[Copilot]

gdi_overlay_hwnd is created as a layered/visible child window, but (in lazy-init cases where has_gdi_content remains false) it never gets a colorkey-applied UpdateLayeredWindow call and there is no WM_PAINT handler anymore. That can leave an opaque overlay painted by DefWindowProc (regression vs the old SetLayeredWindowAttributes path). Consider either (1) calling UpdateLayeredWindow(..., ULW_COLORKEY) once here after the initial FillRect to establish full transparency, or (2) creating the GDI overlay hidden and only showing/updating it after mark_gdi_content_present() flips has_gdi_content true.

Suggested change

	// Ensure the initial GDI overlay is fully transparent by applying the color key once.
	{
	LOGBRUSH lb{};
	COLORREF color_key = RGB(0, 0, 0);
	if (GetObject(g_alpha_mask_brush, sizeof(lb), &lb) == sizeof(lb))
	{
	color_key = lb.lbColor;
	}
	SIZE size = {static_cast<LONG>(ctx->dc_size.width), static_cast<LONG>(ctx->dc_size.height)};
	POINT pt_src = {0, 0};
	UpdateLayeredWindow(ctx->gdi_overlay_hwnd,
	nullptr,
	nullptr,
	&size,
	ctx->gdi_back_dc,
	&pt_src,
	color_key,
	nullptr,
	ULW_COLORKEY);
	}