Stoping a window from scrolling down

I don't understand your question.  Ignoring the part about drag
and drop for now, you are writing your own app in C right?  And,
you are using fopen() to open a file?  And, you are then reading this file into an internal text buffer you control and then
subsequently displaying it in your application's window?

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I have no clue what you are talking about here.  If you are not pulling my leg, either re-post your question from a completely different perspective or post sample code that fails.  'fopen()' has nothing to do with scrolling text windows, so, I fail to see the connection between your question and problem,

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Sorry, there must be some massive mis-communication here.  I go back to my original comment.  I asked you three questions, of which you answered the first two: you are using C, you are calling fopen().  What about my third question?  Furthermore, after you open a file with fopen(), you now have a FILE *.  Your program must be doing something to read the text of the file into a buffer(s) of your application, which your program then displays using TextEdit calls or QuickDraw calls?  Please be specific as to what calls you are making to read and actually display the text of the file.  Excuse me for being condescending, but fopen() does NOT display text to a screen or cause scrolling of displayed text.  So, your problem is not with fopen() in particular.

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