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Project: Drop Files Components.
Unit: PJDropFiles.
Class: TPJCtrlDropFiles
Applies to: ~>5.0
property ManagedControl: TWinControl;
ManagedControl refers to the associated control for which file drops are managed. If this property is nil then no files drops are handled.
At some point between Delphi XE and Delphi 12 TPJCtrlDropFiles stopped working correctly when ManagedControl was associated with a TComboBox or related control. Any attempt to drop a file on the managed control is rejected.
The circumstances under which the bug occurs are not fully understood, depends on the value of the combo box’s Style property as follows:
| TComboBox.Style property value | Behaviour |
|---|---|
csSimple |
File drops are accepted. |
csDropDownList |
File drops not accepted (there is no edit window). |
csDropDown (default) |
File drops not accepted if ManagedControl is set at design time. However, if ManagedControl is cleared then set at run time then File drops are accepted. |
csOwnerDrawFixed |
Not tested, but not expected to work since there is no edit box. |
csOwnerDrawVariable |
Not tested, but not expected to work since there is no edit box. |
For a discussion of the problem see issue #6 in the ddablib/dropfiles repository on GitHub.
One possible way to work around this issue is to use a TPJDropFiles component instead of TPJCtrlDropFiles. Place a TPJDropFiles component on a form and make it the parent of the TComboBox, then size the TPJDropFiles to the same size as the combo box. The TPJDropFiles should then capture file drops made over the the combo box.