Accessing DLLs

Logo provides several commands to ease the direct access to Windows. One of the most interesting features of Logo is its ability to call any routine contained in a Windows DLL. This makes it possible to call virtually any Windows routine, but it also opens the path to writing own routines for Logo, thus enhancing the overall functionality of Logo. The .WINDOWS command converts it inputs to character strings and numbers and passes these values to a routine located within a DLL. In addition to the inputs, you will have to supply the name of the routine to be called. Additionally, you may supply the name of the DLL where the routine is located. Logo recognizes all entry points located in the standard Windows 3.0 and 3.1 DLLs, so there is no need to supply these names.

Besides .WINDOWS, Logo offers access to its internal window handles and device contexts as well as to the Windows messaging system. The .HINST command outputs the instance handle of Logo. The .HWND command outputs the handle of any Logo window, and the .GETDC and .FREEDC commands provides access to the Device Context for the Graphics Window. The .MESSAGE and .WNDPROC commands allow you to intercept Windows messages, and the .WINDOWPOINT and .TURTLEPOINT commands help you in converting between window and turtle coordinates.