function HandleAllocated: Boolean;
bool __fastcall HandleAllocated();
Indicates whether the TCanvas object has acquired a handle to a device context.
Use HandleAllocated to determine whether the Handle property is set to an HDC value. HandleAllocated indicates whether the canvas has acquired a device context. Use HandleAllocated rather than reading the Handle property. When an application reads the Handle property, TCanvas automatically allocates a new device context and returns its handle if the property had not been previously set.