bgiSetCanvasImageShader

Sets a custom image rendering shader for a specific canvas. Searches g_canvasMap for canvasID. If found, sets canvas.activeImageShader = shaderID. If canvas not found, function silently does nothing. No return value.

This function enables per-canvas image shader customization. ShaderID is from image shader loading function. Canvas.activeImageShader is stored in DX12Canvas structure. When b2dSetCanvasFilter is active for this canvas, this shader is used for image rendering (unless overridden by per-draw shader). Allows different image effects per viewport (wireframe in editor canvas, textured in preview canvas). ShaderID 0 means use global image shader (default). Shader persists until changed or cleared. Per-draw shaders (BBR_DrawImageShader) can still override canvas shader. Use for viewport-specific rendering modes, material previews, debug visualizations. Silent failure if canvas doesn't exist. Common pattern: set wireframe shader for editor viewport, standard shader for game viewport.