The huge difference between the first call to Cdialog::onpaint () and the Last Call to Cdialog::onpaint () in the MFC OnPaint () function

The big difference between the first call to Cdialog::onpaint () and the Last Call to Cdialog::onpaint () in the OnPaint () function is that if you do not pay attention to this problem there will be an unreasonable drawing problem-the effect is not coming out! After two hours of torture, the problem lies in the following lessons:

the Cdialog::onpaint () function is called first in the OnPaint () function:

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2. Add a bitmap background to the main form client area
4. void Cbackimagedlg::onpaint ()
6. {
8. Cdialog::onpaint () //First Call
10. CPaintDC DC (this); //device context for painting
14. CRect rect;
16. GetClientRect (&rect);
18. CDC Dcmem; //Define a Toolbox (device context)
22. Dcmem.createcompatibledc (&DC); /// establish an associated DC
24. CBitmap Bmpbackground; //Bitmap Object
26. Bmpbackground.loadbitmap (IDB_BITMAP1); //idb_bitmap is your own figure corresponding to the ID
28. BITMAP BITMAP;
30. Bmpbackground.getbitmap (&BITMAP); //Establish a binding relationship
32. CBitmap *pbmpold=dcmem.selectobject (&bmpbackground); //Save the original CDC object and select the new CDC object into the DC
36. dc. Setstretchbltmode (Coloroncolor); //Prevent BMP image distortion
38. dc. StretchBlt (0,0,rect. Width (), Rect. Height (), &dcmem,0,0, bitmap.bmwidth,bitmap.bmheight,srccopy);
42. Dcmem.selectobject (Pbmpold);
44. Bmpbackground.deleteobject ();
46. Dcmem.deletedc ();
50. }

Running effect: Background bitmap doesn't come out, it's hard to detect what's wrong

The last call to the Cdialog::onpaint () function in the OnPaint () function:

[CPP]View PlainCopy  

2. void Cbackimagedlg::onpaint ()
4. {
6. CPaintDC DC (this); //device context for painting
10. CRect rect;
12. GetClientRect (&rect);
14. CDC Dcmem; //Define a Toolbox (device context)
18. Dcmem.createcompatibledc (&DC); /// establish an associated DC
20. CBitmap Bmpbackground; //Bitmap Object
22. Bmpbackground.loadbitmap (IDB_BITMAP1); //idb_bitmap is your own figure corresponding to the ID
24. BITMAP BITMAP;
26. Bmpbackground.getbitmap (&BITMAP); //Establish a binding relationship
28. CBitmap *pbmpold=dcmem.selectobject (&bmpbackground); //Save the original CDC object and select the new CDC object into the DC
32. dc. Setstretchbltmode (Coloroncolor); //Prevent BMP image distortion
34. dc. StretchBlt (0,0,rect. Width (), Rect. Height (), &dcmem,0,0, bitmap.bmwidth,bitmap.bmheight,srccopy);
38. Dcmem.selectobject (Pbmpold);
40. Bmpbackground.deleteobject ();
42. Dcmem.deletedc ();
46. Cdialog::onpaint (); //Last Call
48. }

Run Effect: Background bitmap effect came out

Summarize:

A code, two positions, two effects! If you are not careful, this error is imperceptible, I used to draw for the client area has been very smooth, but today careless to make this mistake, I spent 2.5 hours to check my code (this project has more than 2000 lines of code!) Start guessing is caused by interference between the code, and finally notice that the position of Cdialog::onpaint () in the OnPaint () function is misplaced! Hey.

Leave a little notes and remind yourself!

http://blog.csdn.net/qq2399431200/article/details/17739087

The huge difference between the first call to Cdialog::onpaint () and the Last Call to Cdialog::onpaint () in the MFC OnPaint () function