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Recently, I was asked to write a thumbnail control to preview a certain
numbers of pictures from a database. At the beginning, I was just lazy and want to
get one over the net. After a few days, unluckily, I still got nothing. With my
boss pressure, I finally have to write it once. Thank you to my boss if you find
this piece of code is useful.
You are suggested to know a little bit about the use of custom control. I
would recommend you to try the MFC Grid Control by Chris Maunder and his great
articles at beginner level about "Creating Custom Controls".
Using the code
Although I have recommended you to have basic knowledge from previous articles, I
will still provide step-by-step instructions to use the control.
Step 1: Create a Dialog resource with a custom control on it.
<p<img src="/KB/miscctrl/ThumbNailCtrl/step1.png" alt="Step 1" width="678" height="487">
Type "CThumbNailControl" in class and "IDC_FRAME_THUMB" in ID
Step 2: Create a class and associate it to the preivous created dialog.
Go to the header file of the class. Insert a include and a variable like below:
class CThumbNailDlg : public CDialog
Step 3: And then go to the cpp file to add the line "DDX_Control(pDX, IDC_FRAME_THUMB, m_cThumbFrame);"
void CThumbNailDlg::DoDataExchange(CDataExchange* pDX)
DDX_Text(pDX, IDC_MSG, m_sMsg);
<code>DDX_Control(pDX, IDC_FRAME_THUMB, m_cThumbFrame);</code>
Step 4: Now, go to OnInitDialog. An initialization is required here. The two integers
are the width and heigh of a thumbnail button. You must call the "m_cThumbFrame.InitializeVariables"
once. The default size is width=100 & height=75.
m_cThumbFrame.InitializeVariables( 200, 150 );
m_cThumbFrame.Add( "fish.bmp" );
m_cThumbFrame.Add( "pinboard.bmp" );
m_cThumbFrame.Add( "chess.bmp" );
m_cThumbFrame.Add( "box.bmp" );
return TRUE; }
Callback for L/R Mouse Clicks
Now, the control is ready to use. You only have to add a few more codes to response to the left and
right mouse clicks (L/R MouseDown). In the header file of your dialog, add the following lines.
afx_msg LRESULT OnTnbLClicked( WPARAM wParam, LPARAM lParam );
afx_msg LRESULT OnTnbRClicked( WPARAM wParam, LPARAM lParam );
In the Message Map section of the dialog cpp file, add...
ON_REGISTERED_MESSAGE( UWM_ON_TNB_LCLICKED, OnTnbLClicked )
ON_REGISTERED_MESSAGE( UWM_ON_TNB_RCLICKED, OnTnbRClicked )
Now, you can add two functions to response to the 2 events.
LRESULT CThumbNailDlg::OnTnbLClicked( WPARAM wParam, LPARAM )
LRESULT CThumbNailDlg::OnTnbRClicked( WPARAM wParam, LPARAM )
Some Known Issues
A smart reader like you may question for the supportted image formats. I am sorry
that the current version could only support the bitmap file. Perhaps in the later
version, I will add the code to support other formats. Interested readers could
could refer to the article "Simple class for drawing pictures (jpg, tif, gif,
etc...)" by Peter Hendrix or any other to integrate the codes together. I would
be grateful if you spend the efforts to help me. ^_^
Another issue is about the calling of AfxMessageBox with mouse clicked action. You have to call
ResetTrackFlag immediately after the popup of message box. I don't have time to deeply resolve it.
Just write one more function to reset the flag. You may refer to and try modify the
CThumbNailDlg::OnTnbRClicked in demo project to see the problem.
If you would like to give me comments and any suggestions, leave me a message or an email.
2002/10/25 Version 1.0 First relese.