Delphi automatically adjusts the ComboBox drop-down list width (PostMessage cb_setdroppedwidth)

Called in the Formshow event of the window where the ComboBox is located

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2. Procedure Setcomboboxlistwidth (Acombobox:tcombobox);
4. Var
6. I:integer;
8. Nmaxlen, nminwidth: integer;
10. Nfontwidth:integer;
12. Ncboleft: integer;
14. Ctlcustom:tcontrol;
16. Begin
18. Ncboleft: = Acombobox.  Left;
20. Ctlcustom: = Acombobox;
22. With acombobox do
24. begin
26. Nfontwidth: = Round (Abs (Font.  Height/ 2));
28. nmaxlen:= 0;
30. For i:=0 to Items. count-1 do
32. begin
34. if Length (items[i]) * nfontwidth > Nmaxlen Then
36. nmaxlen:= length (items[i]) * nfontwidth+5;
38. end;
40. if Items. Count > Dropdowncount Then
42. Nmaxlen: = Nmaxlen + 20;
44. if Nmaxlen > Width Then
46. begin
48. if Items. Count>dropdowncount Then
50. begin
52. SendMessage (Handle, Cb_sethorizontalextent, nmaxlen+5, 0);
56. {Resolution Small causes the width of the comboboxlist to exceed the screen}
58. The //while section is used to remove a ComboBox control relative to the horizontal axis of the form
60. While not (Ctlcustom. Parent is tform) do
62. begin
64. Ncboleft: = Ncboleft + Ctlcustom. Parent.  Left;
66. Ctlcustom: = Ctlcustom.  Parent;
68. end;
70. Nminwidth: = Min (n, Nmaxlen); //Use a number less than Nmaxlen to compare
72. if (ncboleft + nminwidth) > Screen. width- then//do not exceed the screen and keep the window scroll bar width, approx.
74. Nminwidth: = Screen.  width-25-ncboleft;
76. Nminwidth: = Max (Nminwidth, Width); //not less than the width of the control itself
80. PostMessage (Handle, Cb_setdroppedwidth, Nminwidth, 0);
82. End
84. Else
86. PostMessage (Handle, Cb_setdroppedwidth, Nmaxlen, 0);
90. Showhint: = True;
92. End
94. Else
96. begin
98. SendMessage (Handle, Cb_sethorizontalextent, 0, 0);
100. PostMessage (Handle, Cb_setdroppedwidth, Width, 0);
102. end;
104. end;
106. End

http://blog.csdn.net/youthon/article/details/8179348

Delphi automatically adjusts the ComboBox drop-down list width (PostMessage cb_setdroppedwidth)