bgiGetFocusedCanvas

Returns the ID of the canvas that currently has input focus. Returns g_focusedCanvasID value directly. Returns -1 for main window focus, canvas ID (>0) for specific canvas focus, or 0 for no focus.

This function queries which canvas window has keyboard/mouse focus. g_focusedCanvasID is cached from last sysUpdateEvents() call - ensures consistent focus state throughout frame (doesn't query Windows focus directly). -1 indicates main window has focus. Canvas IDs are positive integers from bgiCreateCanvas3D. 0 indicates no BGI window has focus (user clicked outside application). Focus determines which canvas receives keyboard/mouse input. Use for routing input to correct viewport in multi-canvas applications. Common pattern: check focused canvas, only process input for that canvas. sysUpdateEvents() updates focus by tracking WM_SETFOCUS messages. Focus != active render target (active is for rendering, focused is for input). User clicks canvas to give it focus. Alt+Tab or clicking outside removes focus (returns 0).