[教学]：用AcDbDistof()函数后要修改系统变量DBMOD,如何解决?

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通过该教学,朋友们可以学到如何修改只读的系统变量DBMO,可以欺骗ACAD,告诉它图形并没有编辑修改过.

Acdbdistof() modifies the database (dbmod)  
ID    30563  
Applies to:    AutoCAD 2000

Date    6/22/2000  

This document is part of    Visual Lisp   AcDbDatabase   ObjectARX   System Variable     


Question
Whenever there is a call to acdbDisToF() the DBMOD variable is modified, even
though the drawing is not modified.  Why does this occur?
Answer
The implementation of ads_distof() used in AutoCAD R14 was changed in AutoCAD
2000.

In AutoCAD 2000, an AutoCAD variable does the conversion. After finishing the
conversion, it sets the variable back to the previous value, and the result of
the variable change is that DBMOD gets modified.

To solve this problem you can use these two new functions:

AcApDocument::pushDbmod()
AcApDocument::popDbmod()

pushDbmod() saves the current setting of DBMOD, and popDbmod() restores the
value. Between the two calls you can use functions that modify the database.
These functions should be used only to do the drawing initialization when a new
drawing is created, or when a drawing is opened.

Please note that calls to pushDbmod() must be paired with calls to popDbmod().

To solve the problem with acdbDisToF(), you can capsulate the call between the
new functions:
// Before using acdbDisToF() save the current DBMOD value.
curDoc()->pushDbmod();

// Do the conversion.
double value;
acdbDisToF("1.234", 2, &value);

acutPrintf("\nFloat value: %f", value);

// Restore the previous value of DBMOD.
curDoc()->popDbmod();